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Sauropod dinosaurs

January 2011

January 2011

In book: Field Guide to English Wealden Fossils (pp.476–525)
Publisher: Palaeontological Association, London,
Editors: D. J. Batten

Authors:

Paul Upchurch

University College London

Philip David Mannion

University College London

Paul M. Barrett

Natural History Museum, London

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Citation - Upchurch, P., Mannion, P. D, & Barrett, P. M. (2011b). Sauropod dinosaurs. In:

Batten, D. J., Ed.), Field Guide to English Wealden Fossils. Palaeontological

Association, London, 476–525.

SAUROPOD DINOSAURS

by Paul Upchurch1, Philip D. Mannion1 and Paul M. Barrett2

1Department of Earth Sciences, University College London, Gower Street, London, WC1E

6BT, UK; 2Department of Palaeontology, Natural History Museum, Cromwell Road,

London, SW7 5BD, UK; emails: p.upchurch@ucl.ac.uk, p.mannion@ucl.ac.uk and

p.barrett@nhm.ac.uk

SAUROPODS were long-necked herbivorous dinosaurs that dominated many terrestrial

ecosystems during the Jurassic and Cretaceous periods (Upchurch et al. 2004: Text-figs

1, 2). These animals are most famous for their gigantic size: the largest sauropods (such

as Argentinosaurus) reached body lengths of around 30 metres and might have weighed

as much as 50,000 kg (Sander et al. 2011). This group is characterised by numerous

skeletal features (see below), many of which probably relate to either weight bearing or

their herbivorous diets (Upchurch et al. 2004; Harris 2006).

Sauropods originated in the Late Triassic and, by the Middle Jurassic, had achieved

a virtually global distribution (Upchurch et al. 2004). This group apparently suffered a

major extinction at the Jurassic/Cretaceous boundary, losing 60–80 percent of its species

diversity (Upchurch and Barrett 2005; Mannion et al. 2011). During the Cretaceous,

sauropod diversity recovered so that, by the end of this period, species numbers were

similar to those during the heyday of sauropods in the Late Jurassic. However, instead of

broad tooth-crowned forms such as Camarasaurus, mamenchisaurids and turiasaurs

(Gilmore 1925; Pi et al. 1996; Royo-Torres et al. 2006), and the low-browsing narrow-

toothed diplodocids and dicraeosaurids (Hatcher 1901; Janensch 1935–36) that

characterised the Late Jurassic, Early Cretaceous faunas were dominated by

rebbachisaurids and titanosauriform sauropods such as brachiosaurids and titanosaurs

(see Barrett and Upchurch [2005] for an overview of these changes: Text-figs 1-3). This

means that the Early Cretaceous Wealden deposits of the UK are interesting and

important because they mark the early stages of the transition to the titanosaur-dominated

faunas that are common in the Late Cretaceous.

The classification of sauropod dinosaurs is based on our understanding of their

evolutionary relationships (e.g. Wilson 2002; Upchurch et al. 2004; Curry Rogers 2005;

Harris 2006; Wilson and Upchurch 2009; Whitlock in press). A simplified evolutionary tree

is shown in Text-figure 3, with the names of some key sauropod clades marked. For the

purposes of understanding the different varieties of sauropod that occur in the Early

Cretaceous of England, the reader need only be familiar with a few of the major groups

within the Neosauropoda. The latter group includes most Late Jurassic and virtually all

Cretaceous forms and can be regarded as the most advanced and successful sauropod

radiation. Neosauropods are divided into two groups, the Diplodocoidea and Macronaria

(Text-fig. 3). As their name suggests, the Diplodocoidea includes famous animals such as

Diplodocus, a rather lightly built Late Jurassic form that possessed a long low skull,

slender teeth and a whiplash tail (Text-figs 1, 2). The Diplodocoidea is divided into three

families, Rebbachisauridae, Dicraeosauridae and Diplodocidae (Text-fig. 3): to date, only

the rebbachisaurids can be confirmed as present in the Early Cretaceous of the UK. The

apparent absence of diplodocids and dicraeosaurids might simply reflect bad luck in the

sense that we have not yet found them. However, diplodocids and dicraeosaurids might be

genuinely absent from Wealden deposits for evolutionary reasons: diplodocids suffered

severe extinctions at the Jurassic/Cretaceous boundary (see above), and dicraeosaurids

are known mainly from the Southern Hemisphere (Upchurch et al. 2004; Sereno et al.

2007).

Macronaria includes the Titanosauriformes which itself is divided into two important

groups, the Brachiosauridae and Somphospondyli (Text-fig. 3). Brachiosaurids are best

represented by Brachiosaurus and Giraffatitan from the Late Jurassic of North America

and Africa respectively (Text-figs 1D, 2E). These animals had relatively long forelimbs,

which raised their shoulder regions further above ground level and, with the assistance of

a particularly long neck, might have facilitated high-browsing of leaves from tree canopies

(Upchurch and Barrett 2000). The other clade of titanosauriforms, the Somphospondyli

(which includes the Titanosauria) , became very diverse during the Cretaceous and

includes both the smallest and largest known adult sauropods (Sander et al. 2011).

Titanosaurs also possessed relatively slender teeth that resemble those of diplodocoids,

and their pelvic and tail regions may have been specialised in such a way as to allow

these animals to rear up onto their hind limbs (with the tail as the third leg of a ‘tripod’) in

order to increase the height of the head during browsing (Wilson and Carrano 1999).

The gigantic size of sauropod skeletons has left its mark on the quality of their fossil

record. On the one hand, the shear quantity of bone in a sauropod skeleton, and the

robust nature of elements such as the femur, mean that individual bones stand a very

good chance of surviving the fossilization process. On the other hand, the depositional

conditions that characterise most Wealden Supergroup sediments made it very unlikely

that a 30 metre long skeleton would be buried quickly and completely enough for

articulated skeletons and skulls to be preserved. Consequently, the sauropod fossil record

from the Wealden Supergroup consists of a large number of fragments, including isolated

teeth, individual vertebrae and occasional large limb bones, with only rare examples where

several bones are found in association or articulation. The fragmentary nature of Wealden

sauropods in turn means that their taxonomy and nomenclature has become somewhat

complex and confused. This results largely from ‘historical obsolescence’ (see Wilson and

Upchurch 2003), combined with inadvisable taxonomic practices such as erecting new

names for highly incomplete material and the referral of one taxon to another (even when

their type specimens display no anatomical overlap). Where possible, we have retained

existing names in order that the current account can be compared more easily with the

extensive literature on Wealden sauropods, but it should be noted that there are very few

satisfactory diagnoses. Furthermore, we discuss several specimens that are undiagnostic

at the generic and species level (e.g. Rebbachisauridae indet.): this is done so that we can

present a more complete picture of the diversity of Wealden sauropod clades than would

be apparent solely from the list of named taxa.

RECENT DISCOVERIES

Sauropod remains are not particularly abundant in the Wealden Supergroup, but new finds

of isolated bones and teeth are recorded regularly. Notable recent examples from the

Wessex Formation of the Isle of Wight include the discovery of associated limbs from

several different individuals. One of these, consisting of the tibia and complete foot, was

found at Sudmoor Point and donated to the Natural History Museum by Mr Alan Parfitt

(NHMUK R16500). This specimen and an isolated caudal vertebra collected from near

Chilton Chine by Mr David Richards (NHMUK R16483) are currently under study by the

authors and will be described elsewhere. In addition, sauropod limb material is being

excavated from a site between Brook Chine and Hanover Point under the auspices of

Dinosaur Isle Museum (M. Munt, pers. comm., 2011). Several other notable sauropod

specimens from the Isle of Wight are currently held in several private collections (PMB,

pers. obs.).

Sauropod discoveries are less frequent in the mainland Hastings Beds and Weald

Clay Groups, reflecting the closure of many inland quarries and the nature of the

sediments that form the Hastings Beds Group coastal exposures in Sussex, which are

composed principally of durable sandstones, rather than the soft mudstones that comprise

the Isle of Wight Wessex Formation exposures. Nevertheless, there has been a recent

report of a small sauropod tooth collected by Mr Alan Prowse from the upper Wadhurst

Clay Formation of Freshfield Lane Brickworks, near Danefield in West Sussex

(Anonymous 2007). Finally, an isolated sauropod metacarpal was discovered on the

beach at Bexhill by Mr Frank Hamill (Anonymous 2005). The stratigraphical provenance of

this specimen is unknown, but it clearly pertains to one of the horizons in the Hastings

Beds Group. The specimen was originally referred to Diplodocidae (Anonymous 2005), but

it is now regarded as Sauropoda indet. (Mannion et al. in press). As with material from the

Wessex Formation, several sauropod specimens from the mainland Hastings and Weald

Clay Groups are currently in private hands (PMB, pers. obs.).

IDENTIFYING SAUROPOD MATERIAL

Here we present a short introduction to recognising sauropod elements (see Text-Figs 2

and 4-16). Recommended further sources of reading for sauropod anatomy are: Salgado

et al. (1997), Wilson and Sereno (1998), Wilson (2002) and Upchurch et al. (2004).

Sauropod skulls can generally be separated into two categories: short-snouted and high-

domed in basal forms (Text-Fig. 2D,E)), and long-snouted and low-domed in diplodocoids

and titanosaurs (Text-Fig. 2B,C,F). Sauropod teeth possess wrinkled enamel (Text-Figs

15, 16) and show two end-member morphologies. More basal sauropods have spoon-

shaped teeth (e.g. Oplosaurus [Text-Fig. 16]) whereas the teeth of titanosaurs and

diplodocoids are pencil-shaped. Basal titanosauriforms, such as ‘Pleurocoelus’ (Text-Fig.

15), have an intermediate shape. Rebbachisaurid teeth can be distinguished by the

presence of asymmetrical enamel, with the enamel several times thicker on the labial

(outer) than on the lingual (inner) side of the tooth crown (Sereno et al. 1999).

Sauropod necks have at least 12 cervical vertebrae. Cervical centra have strongly

convex anterior ‘balls’ and are concave at their posterior ends (the opisthocoelous

condition) (Text-Fig. 4A, B). They can be distinguished from other elements of the

vertebral column in that the parapophysis (i.e., an elliptical facet for articulation with the

rib) is situated at the anteroventral corner of the lateral surface. The lateral surface

typically possesses a deep pneumatic excavation (‘pleurocoel’ or lateral foramen) that

extends for most of the centrum length (Text-Fig. 4A). Prominent bony ridges (laminae)

are present on the cervical centrum, neural arch and spine (Text-Fig. 4A), and these are

also found in the dorsal (and often sacral and caudal) vertebrae too (see Wilson [1999] for

a thorough treatment of sauropod vertebral laminae). Cervical ribs tend to be extremely

long, extending between one and three times the length of the centrum beyond the

posterior margin of the cervical vertebra; however, diplodocoid cervical ribs are much

shorter and usually do not extend beyond the posterior end of the centrum.

Most sauropods have 12 or 13 dorsal vertebrae, whereas diplodocids (e.g.

Diplodocus) tend to have only 10. The parapophysis moves upwards along the dorsal

sequence and is situated on the lateral surface of the prezygapophyses by most middle-

posterior dorsal vertebrae (Text-Fig. 1C). In most sauropods, the anterior dorsal centra are

opisthocoelous (Text-Figs 12, 13), but the anterior face becomes flat along the dorsal

series. However, in macronarians, this opisthocoely is retained throughout the dorsal

column. Sauropod dorsal centra generally possess large, deep lateral foramina (Text-Figs

12, 13), with this foramen situated within a shallow fossa in titanosaurs (see Xenoposeidon

[Taylor and Naish 2007] for an example). A hyposphene-hypantrum articulation system is

present in the middle-posterior dorsal vertebrae of most sauropods (Text-Fig. 4C), with the

exception of titanosaurs and rebbachisaurids. The hyposphene is a triangular ‘wedge’ of

bone that lies immediately below the postzygapophyses. This ‘wedge’ fits into the

hypantrum, the latter being a slot-like region below and between the prezygapophyses.

The dorsal ribs of titanosauriforms differ from other sauropods in being pneumatic, with

openings present at their proximal ends; they are also plank-like, whereas the ribs of other

sauropods are more rounded in horizontal cross section through their shafts.

The sauropod sacrum consists of five or more co-ossified vertebrae and these often

show similar features to the preceding dorsal vertebrae and succeeding anteriormost

caudal vertebrae. Sauropod tails usually consist of approximately 40-50 caudal vertebrae,

although this number is greatly increased in diplodocids (70-80). The centra of sauropod

caudal vertebrae usually have flat or gently concave articular surfaces (Text-Fig. 4D);

however, in the anterior caudal vertebrae of flagellicaudatans (diplodocids and

dicraeosaurids [Text-Fig. 4E]) and particularly in titanosaurs, the posterior surface

becomes convex (the procoelous condition). The procoelous condition is retained in the

middle caudal vertebrae of derived titanosaurs (Text-Fig. 10). Flagellicaudatans and some

derived titanosaurs also have ‘whiplash’ tails, with distal caudal centra that are four-to-five

times as long as they are high. The middle-posterior caudal vertebrae of titanosauriforms

can be distinguished from other sauropods by their anteriorly shifted neural arches, such

that the posterior half of each centrum is exposed dorsally. Sauropod caudal vertebrae

tend to lack lateral openings, although they are present in diplodocids. Chevrons (or

haemal arches) are present along the anterior-middle portion of the tail, although they are

usually absent in the first few caudal vertebrae. They are composed of two proximal

branches (rami) either side of a haemal canal, with a single distal blade (Text-Fig. 7G). In

most sauropods, the proximal end of the haemal canal is bridged by bone; however the

haemal canal is proximally open in macronarians and non-flagellicaudatan diplodocoids.

The haemal canal usually comprises approximately 25% of the chevron length; however,

this proportion is greatly increased in titanosauriforms, nearing 50% in titanosaurs. With

the exception of titanosauriforms, most sauropods possess forked chevrons in the middle

of their tail (Text-Fig. 4F).

The internal tissue structure of sauropod vertebrae can sometimes be observed

when there is a broken surface. In the presacral vertebrae of most sauropods, it is solid or

a very fine, spongy texture, with occasional large camerae. However, titanosauriform

presacral vertebrae show a ‘honeycomb’-like internal structure (known as camellate) and

this sometimes continues into the sacral and caudal vertebrae (as well as the ilium) in

derived titanosaurs (see Wedel et al. [2000a, b, 2003] for more details on the internal

pneumaticity of sauropods).

The sauropod scapula has a prominent proximal expansion (acromial plate) and a

narrower distal blade. In rebbachisaurids, the blade forms a ‘racquet’-shape (Text-Fig. 6).

Sauropods have long forelimbs, with the humerus approximately 80% of the femur length

in most forms. This value is lower in diplodocoids, whereas the humerus and femur are

close to the same length in brachiosaurids. Sauropod humeri are straight in anterior view,

with transversely expanded proximal and distal ends (Text-Fig. 8). The deltopectoral crest

(which runs along the proximolateral margin of the anterior surface of the humerus)

expands medially in some titanosauriforms, whereas it projects mainly anteriorly in other

sauropods. The distal articular surface of the humerus is anteroposteriorly convex in

titanosaurs, such that it is visible in anterior and posterior view. The proximal end of the

sauropod ulna is triradiate (Text-Fig. 5A). The ulna lacks a bulge on its proximal surface

(olecranon process), but this is present in titanosaurs. The proximal end of the radius

inserts into a deep excavation on the anterior part of the proximal ulna, formed by the

triradiate shape described above (Text-Fig. 5A). The five stout metacarpals are held in a

vertical ‘colonnade’, forming a horseshoe-shaped manus in horizontal cross-section (Text-

Fig. 5B). Sauropods also display extreme reduction of the manual phalanges, except the

claw on the pollex (1st digit); this claw is greatly reduced in titanosauriforms (Text-Fig. 5B)

and all manual phalanges are lost in derived titanosaurs.

The sauropod ilium lacks the brevis shelf and fossa present in other saurischians. The ischial peduncle of the ilium is also

greatly reduced (Text-Fig. 5C). In most sauropods, the anterior process of the ilium tapers to form a

subtriangular outline in lateral view, whereas it is rounded in titanosauriforms (Text-Fig.

5C). The ischial articulation of the pubis is usually approximately 33% of the pubis length

in sauropods (Text-Fig. 14A), but this increases to over 45% in some macronarians. The

pubis is generally shorter than the ischium in most sauropods, but this is reversed in

titanosauriforms (Text-Fig. 14).

The sauropod femoral shaft is straight in anterior and lateral views (Text-Fig. 5D).

The femoral lesser trochanter is generally absent and the fourth trochanter is strongly

reduced. At mid-shaft the femur is anteroposteriorly compressed; this compression is

accentuated in many titanosauriforms, in which the transverse diameter is at least 180%

the anteroposterior diameter. Titanosauriform femora are also distinct from other

sauropods in having a medially deflected proximal third, which produces a lateral bulge

(Text-Fig. 5D). The sauropod tibia has strongly expanded proximal and distal ends, with a

vertically elongate ridge (cnemial crest) projecting laterally from the anterolateral corner of

the proximal end (Text-Fig. 5E). In most neosauropods the distal end has subequal

anteroposterior and transverse diameters, whereas it is anteroposteriorly compressed in

many somphospondylans, as well as some basal sauropods. The medial surface of the

proximal end of the neosauropod fibula bears a striated triangular area and there is a

prominent lateral bulge at approximately mid-height. The sauropod astragalus (i.e. the

major ankle bone) lacks the pit and foramina immediately below the anterior surface of its

ascending process and the medial end is typically strongly reduced both anteroposteriorly

and dorsoventrally (Text-Fig. 5F). The five metatarsals that comprise the sauropod pes

have a spreading morphology (Text-Fig. 5G). Metatarsal I is the shortest and most robust

element in the pes, with a characteristic D-shaped proximal articular end (Text-Fig. 5G).

Metatarsal V is funnel-shaped in dorsal view, with a transversely narrowed distal end

(Text-Fig. 5G). Claws are present on digits I-III and tend to be laterally compressed.

Institutional abbreviations. IWCMS and MIWG, Dinosaur Isle, Sandown, Isle of Wight;

NHMUK, The Natural History Museum, London.

DIPLODOCOIDEA

Introduction

Rebbachisaurids (Text-fig. 1C, 2C) represent a group of basal diplodocoids (Wilson 2002)

whose remains are currently known only from the Cretaceous, although phylogenetic

analyses imply an origination no later than the Late Jurassic (Upchurch and Barrett 2005;

Sereno et al. 2007). The earliest known remains are found in late Hauterivian–early

Barremian deposits from the southwest coast of Croatia (Dalla Vecchia 1998). Barremian-

aged rebbachisaurids are also known from the Isle of Wight (Sereno and Wilson 2005;

Mannion 2009) and Argentina (Apesteguía 2007). Rebbachisaurids reached their peak in

diversity during the Aptian–Cenomanian (Sereno et al. 2007), before going extinct at the

end of the Coniacian (Apesteguía 2007). Members of this family are currently known only

from South America, Africa and Europe (Whitlock in press)).

Rebbachisaurids display a wide range of body sizes, from the gigantic

Rebbachisaurus (approximately 20 m long) to the diminutive Nigersaurus (approximately

9 m long; Text-fig. 1C; Sereno et al. 2007). Members of this clade possess a number of

derived character states, including: asymmetric tooth enamel; the dorsolateral orientation

of transverse processes in dorsal vertebrae; and a racquet-shaped scapula blade (Wilson

2002; Sereno et al. 2007; Whitlock in press). Their skull elements are often extremely thin-

walled and their skeletons are typically lightly built, making them particularly susceptible to

destruction, or poor preservation, as a result of taphonomic processes (Sereno et al. 2007;

Mannion 2009).

Systematic palaeontology

SAUROPODA Marsh, 1878

NEOSAUROPODA Bonaparte, 1986

DIPLODOCOIDEA Marsh, 1884 (sensu Upchurch, 1995)

REBBACHISAURIDAE Sereno et al., 1999

Unnamed rebbachisaurid

Text-figure 6

Material. IWCMS.2001.201–3, teeth (Naish and Martill 2001, pl. 36, figs 1–3); MIWG

5384, a neural arch and spine of an anterior caudal vertebra (Mannion et al. in review);

and MIWG 6544, a portion of scapula blade (Mannion 2009, fig. 2; Text-fig. 6). Although all

belonging to rebbachisaurids, there is no evidence that these separate specimens pertain

to the same individual or taxon.

Locality and horizon. All of the above specimens were found in the vicinity of Brighstone

Bay, Isle of Wight and each pertains to the Wessex Formation (Barremian: Rawson 2006).

Hutt (2001) and Naish and Martill (2001, 2007) stated that the teeth were found at

Sudmoor Point, Isle of Wight: however, the discoverer of these specimens (D. Fowler) has

confirmed that they were actually recovered from Brighstone Bay (D. Fowler, pers. comm.,

2009). More precise information is available on the locality of the portion of scapula: this

was found in a red-brown clay bed at Brighstone Bay, 100m east of Grange Chine

(Mannion 2009, fig. 1).

Discussion. The three teeth (IWCMS.2001.201-3) were illustrated (without description) in

Naish and Martill (2001, pl. 36, figs 1–3), and discussed briefly by Sereno and Wilson

(2005), Naish and Martill (2007) and Mannion (2009). The teeth have slender crowns that

are subcircular in cross-section near the root and become trapezoidal at mid-crown height.

The crowns terminate at the apex in double wear facets in which both the labial and lingual

facets lie at a high angle to the long-axis of the crown. On the basis of these features,

these teeth were identified as probably belonging to a rebbachisaurid diplodocoid by

Sereno and Wilson (2005, p. 170), who noted that they are almost identical to those of

Nigersaurus in terms of shape and wear pattern.

The neural arch and spine of an anterior caudal vertebra (MIWG 5384) has

received little attention previously, even though it possesses a large number of

taxonomically relevant characters. Upchurch (1995) suggested it may have

flagellicaudatan affinities, whereas Hutt (2001) listed it as Sauropoda indet. A recent

review of European diplodocoid material (Mannion et al. in press), however, suggested

that this specimen is probably from a rebbachisaurid (see also Mannion et al. in review).

For example, the ventral margins of the caudal ribs slope dorsolaterally as in other

rebbachisaurids (Whitlock in press). The Isle of Wight specimen retains a hyposphenal

ridge extending from the midline junction of the postzygapophyses to the top of the

posterior neural canal opening: this ridge is present in most eusauropods as well as the

Spanish rebbachisaurid Demandasaurus (PU and PDM, pers. obs., 2009; Torcida

Fernández-Baldor et al. in press), but is lost in all other rebbachisaurids. The presence of

the hyposphenal ridge was interpreted as a derived reversal in the phylogenetic analysis

of Mannion et al. (in press) and we tentatively suggest that the Spanish and Isle of Wight

rebbachisaurids might be closely related (see also Mannion et al. in review).

The portion of scapula (MIWG 6544; Text-fig. 6) was identified as belonging to a

indeterminate rebbachisaurid by Mannion (2009) on the basis of the presence of the

following derived character states: (1) the scapula blade starts to expand dorsally very

close to its junction with the proximal (acromial) plate; (2) in lateral view, the dorsal margin

of the blade reaches, or exceeds, the height of the dorsal margin of the acromial

expansion; (3) the blade expands prominently both dorsally and ventrally (the only non-

rebbachisaurid where this occurs is Haplocanthosaurus); and (4) a hook-like process

projects from the posterodorsal part of the acromial expansion and is separated from the

base of the scapular blade by a ‘U’-shaped concavity in lateral view (see Mannion 2009,

fig 2). In general, the Isle of Wight specimen most closely resembles the scapula of the

Early Cretaceous rebbachisaurid Nigersaurus (Sereno et al. 1999, 2007) according to

Mannion (2009).

A tibia and fibula (MIWG 5308) were found at the same locality as the portion of

scapula, and it has been suggested that they might represent part of the same individual

(Hutt 2001). However, there is no serious basis for their association (S. Hutt, pers. comm.,

2008; Mannion 2009). For example, Brighstone Bay has produced several other sauropod

specimens that almost certainly belong to non-rebbachisaurids, such as titanosauriforms

(see Table 1). The tibia and fibula are therefore provisionally regarded as Eusauropoda

indet. pending further study.

In summary, there is at least one rebbachisaurid in the Wessex Formation of the

Isle of Wight. Although more than one rebbachisaurid taxon could have been present,

there is no strong support for this based on currently available data. The observation that

the scapula and caudal vertebra resemble those of Nigersaurus and Demandasaurus,

respectively, also suggests that the Isle of Wight animal was a member of the

Nigersaurinae subfamily of the Rebbachisauridae (see Whitlock in press; Mannion et al. in

review). Moreover, the neural arch of the anterior caudal vertebra hints at the probability

that the Isle of Wight form is distinct from all other rebbachisaurid taxa (Mannion et al. in

review), though it would be premature to erect a new generic and species name for this

taxon given the extremely incomplete nature of the material to hand.

Other putative diplodocoid remains

Several other Wealden sauropod specimens have been identified as diplodocoids (e.g.

Charig 1980; Blows 1998; Naish and Martill 2001, 2007; Table 1). These include: NHMUK

unnumbered, a tooth (Blows 1998); NHMUK R8924, a forked chevron and NHMUK

R9224, a caudal vertebra (Charig 1980; Naish and Martill 2001, pl. 35, figs 2–4); MIWG

6593, a fragment of ischium (Naish and Martill 2001, p. 234); a metacarpal III or IV from

Bexhill, East Sussex (Anonymous 2005; Naish and Martill 2007); NHMUK R10141, a

‘metatarsal’ (Blows 1998); and NHMUK R11187, a metatarsal I (Upchurch 1995). Recent

taxonomic revisions and reviews (e.g. Upchurch et al. 2004; Upchurch and Mannion 2009:

Mannion et al. in press), however, have cast doubt on the diplodocoid affinities of most of

these specimens. For example, forked or ‘skid’-like chevrons were initially regarded as

highly characteristic of diplodocoids (e.g. McIntosh 1990a), but they are now also known to

occur widely in basal eusauropods as well (Wilson and Sereno 1998; Upchurch et al.

2004; Bandyopadhyay et al. 2010). Thus, forked chevrons probably represent a derived

state that first evolved in basal eusauropods and was retained by most diplodocoids, but

then lost in titanosauriforms and perhaps rebbachisaurids. The occurrence of a forked

chevron in the Early Cretaceous of the Isle of Wight thus indicates the presence of either a

dicraeosaurid or diplodocid, or the persistence of a non-neosauropod lineage beyond the

Jurassic/Cretaceous boundary.

Some of the other specimens can be shown to be non-diplodocoids. For example,

the tooth crown mentioned by Blows (1998, p. 34) as ‘an isolated diplodocid-like tooth from

the Isle of Wight’, is more probably from a titanosauriform (Mannion et al. in press).

Similarly, the caudal centrum (NHMUK R9224) assigned to the Diplodocidae by Charig

(1980) has an anteriorly placed neural arch, a synapomorphy of the Titanosauriformes

(Upchurch et al. 2004; Mannion et al. in press).

The diplodocid identification of the Bexhill metacarpal was rejected by Upchurch

and Mannion (2009, p. 1204), and the fragment of ischium mentioned by Naish and Martill

(2001) is very incomplete and preserves no definitive diplodocoid synapomorphies. The

large metatarsal I (NHMUK R11187) noted by Upchurch (1995) does possess a prominent

laterodistal process, as occurs in flagellicaudatan diplodocoids (Upchurch et al. 2004;

Mannion et al. in press), but this feature is also seen in some brachiosaurids and basal

eusauropods such as Shunosaurus (Upchurch 1998). Moreover, this specimen might

actually come from the Late Jurassic Oxford Clay of Bedfordshire (Mannion et al. in press).

Finally, the ‘metatarsal’ mentioned by Blows (1998, p. 34) is actually a metacarpal IV(?)

that lacks its proximal end. Since there are currently no known diplodocoid

synapomorphies pertaining to metacarpals (Upchurch and Mannion 2009; Mannion et al.

in press), this specimen, and that from Bexhill, cannot be assigned to this group. Recently,

D. Naish (pers. comm. 2011) has noted that the Bexhill metacarpal possesses a flange-

like structure that extends from the distal end along the lateral margin. This is potentially a

derived feature shared with other diplodocids (Bonnan 2001), although similar flanges are

also seen in many titanosaurs (Apesteguía 2005). The phylogenetic significance of this

laterodistal flange requires further detailed evaluation.

For the present, therefore, we suggest that the only convincing evidence for the

occurrence of diplodocoids in the Early Cretaceous of the UK is provided by the

rebbachisaurid specimens discussed above.

TITANOSAURIFORMES

Introduction

Titanosauriformes comprises all sauropods descended from the most recent common

ancestor of Brachiosaurus and Saltasaurus (Salgado et al. 1997). It therefore

encompasses the Brachiosauridae and Somphospondyli, with the latter including

Titanosauria (Text-fig. 3). Collectively, titanosauriforms make up nearly half of known

sauropod diversity, including some 95 valid species (Mannion et al. 2011; Mannion and

Calvo in press). Titanosauriforms are mainly represented by brachiosaurids during the

Middle and, especially, the Late Jurassic (e.g. Riggs 1904; Janensch 1950, 1961),

although ghost ranges and some trackways demonstrate that titanosaurs must also have

been present during the Middle Jurassic (Day et al. 2002, 2004; Upchurch and Barrett

2005; Mannion et al. 2011). During the Cretaceous, somphospondylans (especially

titanosaurs) became increasingly abundant and diverse (Barrett and Upchurch 2005;

Curry Rogers 2005; Upchurch and Barrett 2005; Chure et al. 2010; Mannion and

Upchurch 2010b; Mannion et al. 2011).

Titanosauriforms are characterised by several derived features, including: (1) the

neural arches of middle caudals are anteriorly shifted so that the posterior halves of each

centrum are exposed dorsally; (2) pneumatisation of thoracic ribs; (3) anterior thoracic ribs

have widened ‘plank’-like shafts; (4) reduction or loss of the pollex claw; (5) the anterior

process of the ilium is rounded in lateral view (rather than tapering to form a subtriangular

outline in other sauropods); (6) the long-axis of the ilium is tilted upwards so that the dorsal

margin of the anterior process is the highest part of the element in lateral view; and (7) the

proximal third of the femur is deflected medially (Salgado et al. 1997; Wilson 2002;

Upchurch et al. 2004).

Systematic palaeontology

SAUROPODA Marsh, 1878

NEOSAUROPODA Bonaparte, 1986

TITANOSAURIFORMES Salgado et al., 1997

BRACHIOSAURIDAE Riggs, 1904

Unnamed brachiosaurid

Material. MIWG 7306, a partial cervical vertebra (possibly cervical 6); IWCMS 2003.28, a

poorly preserved vertebra (Naish et al. 2004, figs 2–4).

Locality and horizon. The Wessex Formation (Barremian: Rawson 2006) exposed in the

foreshore between Chilton Chine and Sudmoor Point, Isle of Wight. Naish et al. (2004)

examined matrix adhering to MIGW 7306 and suggested that the specimen probably

eroded out of plant debris bed L1 (see Stewart 1978), which lies immediately above the

Sudmoor Point Sandstone Member at this locality.

Discussion. MIGW 7306 was described and figured by Naish et al. (2004, figs 2–4; see

also Naish and Martill 2001, 2007), and identified as a brachiosaurid sauropod that is

probably more closely related to Sauroposeidon (Wedel et al. 2000a, b) than to Giraffatitan

(Janensch 1914, 1935–36, 1950, 1961; Paul 1988; Taylor 2009). This specimen is a very

large and elongate cervical vertebra that has been damaged and distorted. The internal

structure of this element is composed of variably sized, but generally large, camellate

chambers that resemble those in the cervicals of Giraffatitan (Wedel et al. 2000a, b; Wedel

2003, p. 349). Similar chambers are also present in several diplodocids (Wedel 2003), but

the majority of other sauropods either possess a more dense bone tissue structure or, in

the case of somphospondylans, have numerous small camellae creating an irregular

‘spongy’ texture (Wilson and Sereno 1998). In MIWG 7306 the lateral surface of the

centrum and arch bear a number of pneumatic fossae, and the ‘pleurocoel’ itself is large

and divided by several laminae (as occurs in derived eusauropods such as

mamenchisaurids and neosauropods: Upchurch et al. 2004). The strongest evidence for

assignment of MIWG 7306 to the Brachiosauridae, concerns two potential derived

character states shared with Sauroposeidon: (1) the area occupied by fossae on the

lateral surface of the cervical vertebrae is at least 50 percent of the total area in these

forms; and (2) the posterior centroparapophyseal laminae originate more posteriorly than

in other taxa (Naish et al. 2004). There is also some evidence that the Isle of Wight

specimen represents a distinct taxon, since the cervical diapophysis (i.e. the transverse

process that articulates with the tuberculum of the cervical rib) is broader anteroposteriorly

than in other closely related forms, and there is a unique rhomboidal fossa on the

diapophysis near its posterior edge (Naish et al. 2004). Naish et al. (2004) suggested that

this material was probably referable to one of the named taxa already known from the Isle

of Wight (e.g. Eucamerotus, Ornithopsis or Oplosaurus), but noted that the absence of

overlapping specimens precluded referral at that time. However, the brachiosaurid

affinities of these other Isle of Wight taxa are not as strongly supported (see below) as

those of MIWG 7306, and it is conceivable that the latter specimen represents a distinct

member of the Brachiosauridae.

TITANOSAURIFORMES Salgado et al., 1997

SOMPHOSPONDYLI Wilson and Sereno, 1998

Pelorosaurus conybeari (Melville) Mantell, 1850

Text-Figure 7

Syntypes. NHMUK 28626, a right humerus; NHMUK R2544–2547, four anterior caudal

vertebrae; NHMUK R2548–2550, three anterior chevrons (Melville 1849; Mantell 1850;

Owen 1859; Naish and Martill 2001, fig. 8.9; Text-fig. 7). All of these vertebrae and

chevrons could belong to a single individual, and they were found very close to the

humerus (see below).

Referred material. Mantell (1850) mentioned two ‘middle’ caudals (NHMUK R2166 and

28646a) and a ‘distal’ caudal with chevron still attached (NHMUK R2144).

Locality and horizon. Cuckfield, West Sussex. Grinstead Clay Member of the Tunbridge

Wells Sands Formation, Hastings Beds Group (Valanginian) (Rawson 2006).

Diagnosis. Pelorosaurus conybeari can be distinguished from other sauropods on the

basis of the unusual combination of a long slender humerus with a shallow anconeal

fossa, moderately deep pits or excavations below each caudal rib (Text-fig. 7C, D), and

the absence of a hyposphenal ridge on the anterior caudal vertebrae (Text-fig. 7E, F).

Discussion. The four anterior caudal vertebrae and three chevrons (NHMUK R2544–

2550), and many other vertebrae, were originally identified as belonging to ‘Cetiosaurus

brevis’ by Owen (1842). Most of the specimens assigned to this species were re-identified

as Iguanodon by Melville (1849). Melville concluded, however, that NHMUK R2544–2550

belonged to Cetiosaurus and erected the new species ‘C. conybeari’, even though ‘C.

brevis’ was available and had priority (Ostrom 1970; Steel 1970; Naish and Martill 2001,

2007; Upchurch and Martin 2003; Taylor and Naish 2007; Upchurch et al. 2009). In 1850,

Mantell erected the genus name Pelorosaurus for a large humerus that had apparently

been found ‘a few yards’ away from the place where the caudal vertebrae and chevrons

had been recovered, but he did not mention a specific name. Subsequently, most workers

have accepted that the humerus, caudals and chevrons probably belong to the same

individual and these specimens have generally been known as ‘Pelorosaurus conybeari’

(e.g. McIntosh 1990a; Upchurch et al. 2004), even though ‘Pelorosaurus brevis’ or

‘Cetiosaurus brevis’ might have been more appropriate. One problem is that the name

Cetiosaurus has typically been used to refer to the relatively well-known Middle Jurassic

sauropod exemplified by the type and referred specimens of C. oxoniensis Phillips, 1871

in Oxford and a partial skeleton from Rutland (Upchurch and Martin 2002, 2003). In order

to stabilise this complex nomenclature, Upchurch and Martin (2003) proposed that C.

oxoniensis should be regarded as the type (and currently only) species of Cetiosaurus,

and that the Cuckfield material should be known as Pelorosaurus conybeari. The

designation of C. oxoniensis as the type species of Cetiosaurus has been proposed

formally to the ICZN (Upchurch et al. 2009), whereas the changes required to stabilise the

name of the Cuckfield material need a separate petition. For the present, however, we

follow most recent authors in discussing the Cuckfield material as Pelorosaurus conybeari.

The shaft of the humerus is rather slender relative to its length (transverse width of

shaft at midlength divided by humerus length = 0.12). Damage to the medial margin, and

loss of a large section of the proximolateral portion, means that the precise profile of the

proximal end cannot be determined. The long-axes of the proximal and distal ends are

subparallel, so that the shaft displays little torsion. The deltopectoral crest extends down

the anterolateral margin of the shaft to a point approximately 38 percent of humerus length

from the proximal end. This crest is not especially robust, nor does it expand medially

across the anterior face of the shaft. The concave area at the distal end of the posterior

surface (i.e. the anconeal fossa) is shallow. The anterior caudal centra are amphicoelous

and bear posterolaterally directed caudal ribs (Text-fig. 7). Beneath each rib base, there is

a moderately deep pit, which might represent a pneumatic fossa. The neural spines are

subrectangular in lateral view and are directed posterodorsally. Each postzygapophyseal

facet meets its partner on the midline close to the top of the posterior neural canal

opening: thus, there is no hyposphenal ridge linking this junction to the top of the canal as

occurs in most other sauropods (Upchurch 1995; Upchurch et al. 2004). The chevrons are

‘open’ proximally (i.e. there is no portion of bone linking the left and right rami above the

haemal canal: Text-fig. 7G). The haemal canal is relatively long, occupying approximately

50 percent of chevron length.

NHMUK R2144 is the ‘distal’ caudal with fused chevron mentioned by Mantell

(1850), although it appears to belong to approximately the same part of the tail as the two

‘middle’ caudals NHMUK R2166 and 28646a. These three specimens are labelled as

‘Iguanodon anglicus, previously C. brevis’, but they clearly belong to a sauropod (see

below) and are currently stored with other sauropod specimens in the NHMUK collections.

These caudals are amphicoelous and lack ribs. The neural arches are placed closer to the

anterior end of the centrum than to the posterior end, as occurs in other titanosauriforms

(Upchurch et al. 2004). The chevron of NHMUK R2144 has a tall haemal canal compared

to the total length of the element (however, the precise ratio of haemal canal length to

chevron length cannot be determined in this specimen because the distal part of the blade

is missing). The proximal end of this chevron lacks a ‘bridge’ of bone over the haemal

canal. Similar ‘open’ chevrons were probably also present in the other two middle caudals,

based on the fact that their posterior chevron facets are placed widely apart and separated

by a ‘U’-shaped trough. Despite the relatively distal position of NHMUK R2144, its chevron

was not ‘forked’ or ‘skid’-like. As noted in the discussion of specimen NHMUK R8924 (see

above), ‘forked’ middle chevrons probably represent the plesiomorphic condition for

eusauropods, suggesting that the unforked nature of NHMUK R2144 probably represents

the derived state seen in titanosauriforms. There is no evidence that these three middle

caudals were found in close association with the type humerus and caudals. Nevertheless,

the morphology of the type material of Pelorosaurus conybeari and the three middle

caudals from Cuckfield is consistent with them belonging to a single basal titanosauriform

taxon (see below).

Pelorosaurus conybeari has played a significant role in the complex taxonomic

history of Wealden sauropods. Lydekker (1888a) assigned numerous other specimens

(e.g. teeth, NHMUK 20004–5, R1610; a caudal vertebra, NHMUK 28646; and the shaft of

a smaller left humerus, NHMUK R713) to Pelorosaurus conybeari: however, the teeth

cannot be compared with the type material, and the caudal and humerus do not display

the required diagnostic features (see Naish and Martill 2001). Next, Lydekker (1890a, b,

1892) argued that the four anterior caudals that had previously formed the type material of

Cetiosaurus brevis, along with ‘Bothriospondylus robustus’ and the forelimb of

‘Pelorosaurus becklesii’ (see below), all belonged to the same species of ‘Morosaurus’ (as

‘M. brevis’). Later still, Lydekker (1893) suggested that the dorsal vertebra NHMUK R2095,

which is now the holotype of Xenoposeidon, was referable to Pelorosaurus, but the

evidence used to justify this is inadequate (Taylor and Naish 2007).

The diagnosis of Pelorosaurus conybeari is unsatisfactory (Blows 1995, 1998;

Naish and Martill 2007). Diagnostic characters have been proposed by Blows (1995) and

Upchurch et al. (2004), but they provide only weak evidence for the distinctness of

Pelorosaurus conybeari at the global scale. For example, the anconeal fossa at the distal

end of the posterior surface of the humerus is relatively shallow, but this is a subtle feature

and difficult to quantify and compare with other taxa. At present, however, Pelorosaurus

conybeari is the only taxon that combines an elongate slender humerus with caudal

vertebrae that lack a hyposphenal ridge and possess moderately deep depressions on the

lateral surface of the centrum immediately below the base of each rib.

The very elongate humerus, the absence of hyposphenal ridges on the anterior

caudal vertebrae, and presence of the tall haemal canals (see above), all support the

placement of Pelorosaurus conybeari within the Titanosauriformes (Curry Rogers and

Forster 2001; Upchurch and Martin 2003), but its position within this clade is unclear.

McIntosh (1990a) and Naish and Martill (2001) identified Pelorosaurus as a brachiosaurid,

based on features such as the elongate shape of the humerus and its well-developed

deltopectoral crest. However, Taylor and Naish (2007) noted that the type humerus differs

from those of Brachiosaurus and Giraffatitan in having a less well-developed deltopectoral

crest. Given that Wilson and Sereno (1998) argued that the large deltopectoral crest is a

brachiosaurid synapomorphy, the brachiosaurid affinities of Pelorosaurus might be called

into question. Similarly, although elongate humeri are certainly present in brachiosaurids

such as Brachiosaurus and Giraffatitan, they also occur in forms such as Chubutisaurus

which, according to some studies (e.g. Salgado et al. 1997) is more closely related to

titanosaurs. Salgado and Calvo (1997) suggested that Pelorosaurus is more closely

related to Titanosauria than to Brachiosauridae. This view received support from Upchurch

and Martin (2003) who noted that the caudal vertebrae of Pelorosaurus lack a

hyposphenal ridge as is also the case in several somphospondylan genera (e.g.

Alamosaurus, Isisaurus and Saltasaurus). Here, therefore, we provisionally regard

Pelorosaurus conybeari as a valid, but currently very poorly diagnosed, basal

titanosauriform that is potentially more closely related to Somphospondyli than to

Brachiosauridae.

Xenoposeidon proneneukos Taylor and Naish, 2007

Holotype. NHMUK R2095, a partial dorsal vertebra that preserves the centrum and base

of the neural arch (Lydekker 1893, fig. 1; Taylor and Naish 2007, figs 3–5).

Locality and horizon. Ecclesbourne Glen, East Sussex. Ashdown Formation, Hastings

Beds Group (late Berriasian–Valanginian: Rawson 2006). There is uncertainty surrounding

the locality from which NHMUK R2095 was recovered. Taylor and Naish (2007) present

some circumstantial evidence to support the proposed provenance from Ecclesbourne

Glen. Interestingly, however, the ‘Discussion’ at the end of Lydekker’s report before a

Geological Society of London audience includes a comment in which this specimen is

referred to as “…the new vertebra from Tilgate” (H. G. Seeley in Lydekker 1893, p. 280).

Nevertheless, as noted by D. Naish (pers. comm., 2011), Lydekker specifically stated that

this specimen came from a locality near Hastings, suggesting that Seeley’s mention of

‘Tilgate’ is probably an error.

Diagnosis. Taylor and Naish (2007) diagnosed Xenoposeidon on the basis of the

following autapomorphies: (1) the neural arch covers the dorsal surface of the centrum,

with its posterior margin continuous with that of the posterior articular face; (2) the neural

arch slopes anteriorly at 35° to the vertical; (3) a broad, flat featureless area occurs on the

lateral face of the neural arch; (4) accessory centroparapophyseal and

centropostzygapophyseal laminae meet ventrally to form a an inverted ‘V’-shape; (5) the

neural canal is asymmetrical (small and circular posteriorly, but tall and teardrop-shaped

anteriorly); (6) supporting laminae form a vaulted arch over the anterior neural canal

opening.

Discussion. NHMUK R2095 consists of the centrum (lacking its anterior articular face)

and damaged neural arch of a dorsal vertebra. The lateral pneumatic fossa has a rounded

subtriangular outline and ramifies deeply within the centrum. Internally, the tissue structure

of the bone appears to be formed from relatively large camerae, as occurs in some

diplodocoids and brachiosaurids (Wedel 2003). Few details can be gleaned from the

neural arch region because the zygapophyses, diapophyses and neural spine are missing.

The arch clearly bore several laminae on its lateral surfaces that presumably supported

structures such as the parapophyses and diapophyses from below, but their precise

homologies with those seen in other sauropods are difficult to ascertain. The fact that the

parapophysis cannot be detected implies that this structure lay in a relatively high position,

suggesting that this specimen represents a middle or posterior dorsal vertebra. As noted

by Taylor and Naish (2007), there are well-developed centroprezygapophyseal laminae

that form a vaulted concavity over the anterior neural canal opening.

Taylor and Naish (2007) argued that Xenoposeidon possesses a mosaic of

character states that make it difficult to place within any of the currently recognised

sauropod clades. For example, these authors noted that NHMUK R2095 has a relatively

elongate centrum, as also occurs in the posterior dorsal vertebrae of brachiosaurids. In

contrast, the lateral pneumatic opening lies within a fossa as is seen in many titanosaurs

but not brachiosaurids (Bonaparte and Coria 1993; see also Mannion and Calvo in press).

However, placement within the Somphospondyli is itself also problematic because

Xenoposeidon lacks the camellate tissue structure that characterises this clade (Wilson

and Sereno 1998). Taylor and Naish (2007) therefore identified Xenoposeidon as

Neosauropoda incertae sedis. The view that Xenoposeidon represents an enigmatic and

potentially new group of sauropods was further reinforced by these authors’ phylogenetic

analysis which failed to place this genus in a single stable position. Here, we tentatively

regard NHMUK R2095 as belonging to a very basal somphospondylan. This view is

supported by the position of Xenoposeidon in Taylor and Naish’s (2007) majority-rule

cladogram.

TITANOSAURIFORMES Salgado et al., 1997

SOMPHOSPNDLYI Wilson and Sereno, 1998

TITANOSAURIA Bonaparte and Coria, 1993

‘Pelorosaurus becklesii’ Mantell, 1852

Text-Figures 8 and 9

Type material. NHMUK R1870, an associated right humerus (Text-fig. 8), ulna and radius;

NHMUK R1868, a portion of skin impression from near the elbow region (Text-fig. 9)

(Mantell 1852).

Locality and horizon. Hastings, East Sussex. An undetermined horizon within the

Hastings Beds Group (late Berriasian–Valanginian: Rawson 2006).

Discussion. The humerus of ‘Pelorosaurus becklesii’ resembles those of other sauropods

in its general form and proportions. The deltopectoral crest bears a smaller crest lying on

the longitudinal ridge extending down the anterolateral margin of the bone. As in most

sauropods, the cross-sectional profile of the mid-shaft region is compressed

anteroposteriorly rather than being subcircular. The excavated area on the distal part of

the posterior face of the shaft (i.e. the anconeal fossa) is deep, unlike that in Pelorosaurus

conybeari. The anteromedial corner of the distal end of the humerus bears a small,

anteriorly directed process (Text-fig. 8D) that is usually absent in other sauropods. Another

slightly unusual feature is that the distal end of the humerus projects almost as far medially

as does the proximal end. The ulna and radius are short and relatively robust elements.

There is a distinctly concave profile to the anteromedial process of the proximal end of the

ulna in medial view. The shaft of the ulna bows slightly medially and anteriorly. The distal

end of the ulna expands slightly transversely and much more prominently

anteroposteriorly. In transverse cross-section, the radial shaft is oval with the long-axis of

this section directed transversely. The shaft bows slightly anteriorly and medially. The

distal end is a little larger than the proximal one, and is convex and rugose. The skin

impression consists of numerous small polygonal 'ossicles' which range in size from

approximately 10–25 mm in diameter (Text-fig. 9; see also Hooley 1917, fig. 2; Czerkas

1994). They may have become smaller towards the elbow joint, presumably allowing

greater flexibility. Steel (1970) suggested that the convex surfaces of these ossicles (the

side that is exposed) actually faced inwards towards the limb bones, based on the

observation that their flat surfaces are covered by matrix. However, analogy with the

dermal remains found with Saltasaurus (Bonaparte and Powell 1980), suggest that the

exposed convex surfaces might represent the exterior of the skin.

Marsh (1889) referred ‘Pelorosaurus becklesii’ to the North American genus

‘Morosaurus’ to create the combination ‘M. becklesii’. The nomenclature of this form was

further complicated by Nicholson and Lydekker (1889) and Lydekker (1890a, 1893), who

accepted that ‘Cetiosaurus brevis’, the caudals of Pelorosaurus conybeari and ‘M.

becklesii’ were congeneric and so created the new combination ‘M. brevis’ (see also

Swinton 1934, 1936). The referral of ‘Pelorosaurus becklesii’ to ‘Morosaurus’ cannot be

supported as ‘Morosaurus’ is now recognised as a junior synonym of Camarasaurus, and

there are no diagnostic features shared by this North American taxon and ‘P. becklesii’

(Taylor and Naish 2007).

Upchurch (1995) and Upchurch et al. (2004) noted that the deep anconeal fossa

between well-developed ridges, very robust forearm bones, the concave profile of the

anteromedial proximal process of the ulna, and the structure of the skin impression, all

support the view that ‘P. becklesii’ is a titanosaur. The morphology of the distal end of the

humerus is potentially diagnostic, suggesting that ‘Pelorosaurus becklesii’ deserves a new

generic name (though see Naish and Martill 2007, p. 499). However, we refrain from

naming a new taxon until more comparative data are available. At present, therefore, we

regard ‘P. becklesii’ as a potentially distinct titanosaur, which, given its late Berriasian or

Valanginian age, would make it one of the earliest known body fossils of this group from

the Northern Hemisphere.

Iuticosaurus valdensis’ (von Huene) Le Loeuff, 1993

Lectotype. NHMUK R151, a waterworn middle caudal vertebra (Lydekker 1887, fig. 22; Le

Loeuff 1993; Naish and Martill 2001, fig. 8.15). There is some confusion in the literature

concerning which specimens represent the holotype, lectotype and paralectotype. Le

Loeuff (1993) stated that NHMUK R151 should be regarded as the lectotype and R1886

(see below) as the paralectotype. Naish and Martill (2001) also listed R151 as the

lectotype and R1886 as the holotype. However, von Huene (1929) originally listed only two

specimens, R146a and R151 as belonging to ‘Titanosaurus valdensis’. We suggest,

therefore, that these two specimens represent the type series, and the designation of

R151 as the lectotype by Le Loeuff (1993) means that R146a should be regarded as the

paralectotype. Since NHMUK R1886 was not part of the original type series, it is more

appropriate to regard this as a referred specimen rather than the ‘holotype’ contrary to the

proposal of Naish and Martill (2001, fig. 8.14).

Paralectotype. NHMUK R146a, the anterior part of a middle caudal vertebral centrum.

Referred material. NHMUK R1886, a caudal vertebra (Le Loeuff 1993; Blows 1998, fig.

6B; Naish and Martill 2001, fig. 8.14). The legend to fig. 8.14 in Naish and Martill (2001)

lists ‘R151’, but it is clear from the presence of a neural arch and postzygapophyses that

the figured specimen is actually NHMUK R1886.

Locality and horizon. NHMUK R146a and R151 come from Brook, Isle of Wight (Blows

1995), but R1886 is from an unknown locality on the Isle of Wight (Le Loeuff 1993; Naish

and Martill 2001). Some confusion regarding the stratigraphic age of these specimens has

crept into the recent literature. Le Loeuff (1993) suggested that R146a and R151 were

found in rocks of Barremian–early Aptian age, but, as noted by Naish and Martill (2001, p.

225) the Brook locality is consistent with recovery from the Wessex Formation. The legend

for fig. 8.14 in Naish and Martill (2001, p. 225) also stated that R151 (actually R1886, see

above) comes from the ‘Upper Greensand’ - this is incorrect and presumably a

typographical error. All of these specimens are most likely to have pertained to the

Wessex Formation (Barremian: Rawson 2006).

Discussion. These three specimens have elongate, transversely compressed and

strongly procoelous centra. There are no caudal ribs, and their general proportions

suggest that these specimens came from the middle of the tail. The neural arch is located

on the anterior half of the centrum, as occurs in other titanosauriforms (Upchurch et al.

2004). The postzygapophyses are situated on the posteroventral part of a posteriorly

directed neural spine that curves slightly ventrally towards its terminus in lateral view. As a

result, the postzygapophyses are unusual insofar as they terminate close to the posterior

end of the centrum (Le Loeuff 1993).

Lydekker (1887) referred NHMUK R146a and R151 to Ornithopsis, but later

identified them as ‘Titanosaurus sp. a’ (Lydekker 1888a). Von Huene (1929) erected the

new species ‘T. valdensis’ in order to distinguish the Isle of Wight taxon from other species

within that genus. However, referral to ‘Titanosaurus’ cannot be supported (Wilson and

Upchurch 2003) and Le Loeuff (1993) created the new taxon ‘Iuticosaurus valdensis’ on

the basis of several putative diagnostic features that distinguish the type specimens and

NHMUK R1886 from other taxa. These features are: (1) there is a ridge on the lateral

surface of the centrum that leads into a flattened area on the dorsal surface posterior to

the neural arch: and (2) the postzygapophyses are apomorphically long. However, these

features are seen in at least some other titanosaurs such as Aeolosaurus (Salgado et al.

1997). Naish and Martill (2001, 2007), Wilson and Upchurch (2003) and Upchurch et al.

(2004) therefore regarded ‘Iuticosaurus’ as a nomen dubium.

The presence of a strongly convex posterior articulation in middle caudal vertebrae

suggests that ‘Iuticosaurus’ is a derived titanosaur (Jacobs et al. 1993; Upchurch et al.

2004; Curry Rogers 2005). The current uncertainties surrounding many aspects of

titanosaur phylogeny (e.g. Curry Rogers 2005; Mannion and Upchurch 2011) make it

difficult to identify the relationships of ‘I. valdensis’ within Titanosauria more precisely.

However, most titanosaurs possess middle caudal centra that are either subcircular or

dorsoventrally compressed in transverse cross-section. A subset of taxa (including ‘I.

valdensis’, ‘Titanosaurus indicus’ and Aeolosaurus) possesses characteristically

transversely compressed caudal centra (Salgado and Coria 1993; Wilson and Upchurch

2003), and perhaps represent members of a monophyletic group. Le Loeuff (1993) argued

that the apparent lateral compression of the caudal centrum (which is particularly strongly

developed in NHMUK R151) is an artefact created by water-based erosion. Even if this is

correct, however, the apomorphically long postzygapophyses shared by ‘I. valdensis’ and

Aeolosaurus support a close phylogenetic relationship.

Salgado and Calvo (1997) suggested that ‘I. valdensis’ is the earliest known

titanosaur, and Mannion et al. (2011) identified it as the earliest known lithostrotian (Text-

fig. 3). Such claims depend heavily on how these clades are defined and which

phylogenetic topology is preferred. Moreover, ‘Pelorosaurus becklesii’ might represent an

even earlier member of one of these clades. Nevertheless, ‘I. valdensis’ provides another

example where the Wealden fauna contributes to our understanding of sauropod evolution

at a global scale.

Unnamed taxon, Titanosauria indet.

Text-Figure 10

Material. NHMUK R5333, conjoined portions of three caudal vertebrae (Blows 1998, fig.

6C; Text-fig. 10).

Locality and horizon. Brook, Isle of Wight. Wessex Formation (Barremian: Rawson

2006).

Discussion. NHMUK R5333 comprises two middle caudal vertebrae and the posterior

articular ‘ball’ of a third caudal. These vertebrae are preserved as a unit, indicating that

they form a natural sequence from a single individual. The centra are strongly procoelous,

but, unlike ‘Iuticosaurus valdensis’, they are subcircular in transverse cross-section rather

than being laterally compressed. This suggests that NHMUK R5333 probably represents a

second derived titanosaur in the Wessex Formation. To date, no diagnostic features have

been reported for NHMUK R5333 and it is therefore regarded as Titanosauria indet.

(Blows 1998).

TITANOSAURIFORMES Salgado et al., 1997

incertae sedis

‘Chondrosteosaurus gigas’ Owen, 1876

Type material. NHMUK 46869 and 46870, two cervical centra (Owen 1876, pls 2–5).

Owen (1876) only described NHMUK46869, but Lydekker (1888a) and Ostrom (1970)

argued that other specimens, such as NHMUK 46870, are part of the type series. This is

because Owen (1876) mentions NHMUK 46870 in his description of ‘C. magnus’, but in

his Plate 5 this specimen is referred to as ‘C. gigas’ (see Naish and Martill 2001).

Locality and horizon. Locality uncertain, south coast of the Isle of Wight. Wessex

Formation (Barremian: Rawson 2006).

Discussion. Owen (1876) noted that the ‘Chondrosteosaurus gigas’ cervicals are

opisthocoelous, dorsoventrally flattened and have broad, flat ventral surfaces. These

features, coupled with the presence of a separate parapophysis and diapophysis, led him

to suggest that these vertebrae came from the anterior part of the trunk. However, the

parapophysis is situated anteroventral to the anterior end of the lateral pneumatic fossa,

and the latter is divided by an anterodorsally slanting oblique lamina. These two features

suggest that the centra came from cervical rather than anterior dorsal vertebrae (Upchurch

et al. 2004). NHMUK 46870 has been sectioned sagittally and polished, revealing that it

possessed large camellate chambers ramifying throughout much of the bone (Owen 1876,

pl. 5; Naish and Martill 2001, figs 8.4–8.5; Naish 2010: fig. 4). These chambers are

irregular in shape and separated by thin sheets of bone.

The extremely incomplete nature of the ‘C. gigas’ material makes it very difficult to

determine its affinities with other sauropod taxa. McIntosh (1990a) noted that ‘C. gigas’

vertebrae most closely resemble the tenth cervical vertebra of Camarasaurus. Until

recently, most workers accepted McIntosh’s identification of ‘Chondrosteosaurus’ as some

form of camarasaurid sauropod (e.g. Olshevsky 1991; Upchurch 1993, 1995; Insole and

Hutt 1994; Hunt et al. 1994; Canudo et al. 2002). This view is supported by some limited

character data. For example, Upchurch (1993, 1995) noted that brachiosaurids and

diplodocids typically possess cervical centra that are transversely concave on their ventral

surfaces because of the presence of distinct ventrolateral ridges, but these structures are

absent in Camarasaurus and ‘Chondrosteosaurus’. Moreover, brachiosaurid and

mamenchisaurid cervicals tend to be more elongate and the pneumatic fossae of the

former are often divided by multiple laminae rather than a single oblique lamina. However,

the camerae observed in ‘Chondrosteosaurus’ typically occur in basal titanosauriforms

(Wedel 2003) and it has therefore been suggested that ‘C. gigas’ might actually be a

member of this clade (pers. comm. from P. Upchurch cited in Dalla Vecchia 1998; pers.

comm. from M. Wedel cited in Naish and Martill 2007; Naish 2010).

No diagnostic features can be recognised in ‘C. gigas’, and it is therefore regarded

as an indeterminate basal titanosauriform here (see also Naish and Martill 2001).

Eucamerotus foxi Hulke, 1871

Text-Figures 11 and 12

Holotype. NHMUK R2522, a partial dorsal neural arch (Hulke 1870, pl. 22, figs 1–4; Hulke

1871; Blows 1995, fig 1C; Text-fig. 11).

Paratypes. NHMUK R88 (Naish and Martill 2007, fig. 5a–c), R89 (Text-fig. 12), R90 and

R2524, five dorsal vertebrae (Blows 1995, pl. 1, figs 1–6; Naish and Martill 2001, pl. 34,

figs 1–3). It is possible that NHMUK R89 and R90, as well as some cervical vertebrae (e.g.

NHMUK R87 and R87a) belong to a single individual, although there is no direct evidence

for their association in the field (Blows 1995, p. 192).

Referred material. NHMUK R91, R2523, R406, R708, six dorsal vertebrae and two

centra. Blows (1995, p. 190) and Naish and Martill (2001, pp. 218–220) also listed several

specimens with MIWG numbers. The latter include the privately-owned ‘Barnes High

sauropod’ specimen that was referred to Eucamerotus by Blows (1995, 1998), but which is

provisionally regarded as a separate form here (see below).

Locality and horizon. Brook Bay, Isle of Wight. Wessex Formation (Barremian: Rawson

2006).

Diagnosis. Eucamerotus foxi can be diagnosed on the basis of the following

autapomorphies in the middle and posterior dorsal vertebrae: (1) presence of a shallow

longitudinal fossa on the lateral surface of the neural arch, paralleling the posterior part of

the dorsal margin of the lateral pneumatic fossa (‘pleurocoel’); and (2) the

prezygapophyses are connected to the parapophyses by two parallel and sub-horizontal

ridges that are separated from each other by a shallow fossa (PU, pers. obs., 2011: Text-

fig. 11A).

Discussion. Hulke published the name Eucamerotus in 1871 without designating a type

species. In 1995, Blows identified a series of putative diagnostic features in Hulke’s

original type specimen (NHMUK R2522), erected the species name E. foxi, and identified

a number of paratypes and referred specimens (all dorsal vertebrae). The centra of these

dorsal vertebrae are opisthocoelous, with a moderately well-developed convex anterior

articular surface (Text-fig. 12). Each centrum has a broad, flat ventral surface and the

pneumatic fossae (‘pleurocoels’) are large and deep. These fossae are subtriangular in

outline, with a bluntly rounded tall anterior margin and acute posterior end. Each fossa

ramifies throughout the centrum, and numerous small accessory laminae form the borders

between internal chambers. In at least some specimens (e.g. the two paratypes numbered

NHMUK R90), there is a potentially autapomorphic feature: this is a small elongate fossa

that extends parallel to the posterior margin of the dorsal part of the ‘pleurocoel’,

separated from the latter by a rounded ridge. The stout centroprezygapophyseal laminae

form the lateral walls of a deep cavity on the anterior surface of the tall neural arch. The

centroprezygapophyseal laminae bifurcate at their upper ends. The thinner lateral lamina

created by the bifurcation probably supported the parapophysis from below. Each

parapophysis lies close to the level of the prezygapophyses in the middle and posterior

dorsals. Another potentially unique feature is the presence of two parallel and nearly

horizontal ridges, separated by a shallow fossa, that link the lateral surface of the

prezygapophysis to the parapophysis, whereas in other sauropods such a connecting

lamina is usually single (Text-fig. 11A). The transverse processes project outwards and

moderately upwards, at an angle that is a little steeper than that seen in Brachiosaurus

and Giraffatitan (Riggs 1904; Janensch 1950). The broad plate, which forms this process,

is supported from below by a stout posterior centrodiapophyseal lamina. Posterior to the

latter lamina, within the infrapostzygapophyseal cavity, there is often an accessory lamina

running posterodorsally to support the postzygapophysis from below. The main

centropostzygapophyseal laminae run dorsomedially in posterior view, and meet the

ventrolateral corners of the hyposphene: this creates the deep cavity above the posterior

neural canal opening noted by Blows (1995). The neural spine is composed of

spinoprezygapophyseal laminae and very strongly developed lateral laminae that are

formed by the conjoined spinopostzygapophyseal and spinodiapophyseal laminae. This

combined spinopostzygo-spinodiapophyseal lamina runs upwards and expands outwards

as it approaches the summit. This expansion forms a prominent triangular process, which

is directed laterally. On the posterior surface of the spine, there is a deep postspinal cavity

created by the combined spinopostzygo-spinodiapophyseal laminae. The posterior surface

of the spine frequently displays a midline postspinal lamina, but this is not as well-

developed as those in diplodocoids and titanosaurs.

An error concerning the accession number of one Eucamerotus foxi specimen has

appeared in the literature and is corrected here. NHMUK R88 (Hulke 1880, pl. 4) is a

dorsal vertebra that was referred to Eucamerotus by Blows (1995). However, Blows stated

that this specimen is one of two vertebrae with the number NHMUK R89 (see Blows 1995,

pl. 1, figs 1–2). Further confusion has been caused by the fact that R88, which is on public

display at the NHMUK, was mislabelled in the exhibition as R90. However, detailed

examination of the NHMUK catalogue, the early literature (e.g. Hulke 1880; Lydekker

1888a) and the specimens themselves, demonstrates that the two Eucamerotus dorsal

vertebrae on display are R88 and R89, there is only one dorsal registered under R89, and

the two dorsals numbered R90 remain in storage in the NHM collection.

The status of Eucamerotus foxi is controversial. For much of the late nineteenth and

twentieth centuries, this taxon was regarded as referable to either Ornithopsis or

Pelorosaurus (e.g. Hulke 1882; Steel 1970). More recently, such referrals have been

rejected (e.g. Blows 1995; Naish and Martill 2001, 2007; Upchurch et al. 2004) but there

remains disagreement concerning whether E. foxi is a valid species or nomen dubium.

Blows (1995) argued that a suite of diagnostic features justified the recognition of E. foxi

as a taxon that is distinct from all other apparently similar sauropods (e.g. Ornithopsis and

Brachiosaurus). Naish and Martill (2001, 2007) and Upchurch et al. (2004) suggested that

all of these diagnostic features are unsatisfactory because they occur among several other

sauropod taxa. Here, however, we note two new features observed in E. foxi that appear

to be diagnostic, given the comparative data currently to hand (see above). We therefore

retain Eucamerotus foxi as a potentially valid taxon.

Most workers have regarded Eucamerotus as a brachiosaurid (Blows 1995, 1998;

Naish and Martill 2001, 2007; Taylor and Naish 2007). There are, however, several

significant problems with such a precise identification. First, Eucamerotus is only known

from dorsal vertebrae at present, but there are few compelling synapomorphies of the

Brachiosauridae that have been recognised in this part of the skeleton (Upchurch et al.

2004). Recent phylogenetic analyses focusing on basal titanosauriform relationships (e.g.

Rose 2007; Chure et al. 2010; Ksepka and Norell 2010) have reported no dorsal vertebral

synapomorphies for Brachiosauridae or clades within this family. Taylor (2009) listed three

synapomorphies, but two of these (neural spines become taller and transverse processes

become larger and more robust towards the anterior end of the dorsal series) cannot be

assessed in E. foxi because of the lack of an articulated sequence of dorsals. The third

feature noted by Taylor (the absence of bifurcation of the centroprezygapophyseal

laminae) is not present in E. foxi (see above), which thus fails to support inclusion of this

taxon in the Brachiosauridae. The second problem is that the taxonomic contents of

Brachiosauridae are currently poorly understood. This family is defined as all taxa more

closely related to Brachiosaurus altithorax than to Saltasaurus loricatus (Bonaparte and

Powell 1980; Wilson and Sereno 1998; Taylor 2009). Brachiosauridae probably represents

a monophyletic clade (though see Salgado et al. 1997) that contains at least

Brachiosaurus, Giraffatitan, Sauroposeidon, and Abydosaurus (Chure et al. 2010), but

many other taxa (such as Cedarosaurus, Chubutisaurus and Lusotitan) that have

previously been assigned to this family might actually be basal titanosauriforms that are

more closely related to Titanosauria than to Brachiosauridae (e.g. Rose 2007; Ksepka and

Norell 2010). Without a clearer picture of the taxonomic contents of Brachiosauridae, it is

difficult to determine which character states diagnose this clade and its constituent

members. Moreover, Santucci and Bertini (2005) have proposed that E. foxi is more

closely rlated to somphospondyli than to Brachiosauridae. Thus, pending the publication of

more detailed phylogenies of basal titanosauriform relationships, and the description or re-

evaluation of key specimens such as Lusotitan and the ‘Barnes High sauropod’, we prefer

the more conservative identification of Eucamerotus as a basal titanosauriform (lying

outside Titanosauria), as proposed by Upchurch et al. (2004).

Ornithopsis hulkei Seeley, 1870

Text-Figure 13

Lectotype. NHMUK 28632, a portion of anterior dorsal vertebra (Owen 1875, pls 8–9;

Blows 1995, fig. 1A–B; Text-fig. 13; Naish 2010: fig. 3). Blows (1995) identified this

specimen as a posterior dorsal, but it is regarded as an anterior dorsal herein (see below).

Locality and horizon. Chilton Chine, Brook Bay, Isle of Wight. Wessex Formation

(Barremian: Rawson 2006).

Diagnosis. Ornithopsis hulkei can be diagnosed on the basis of the following

autapomorphies: (1) the centrum is taller than wide; (2) the ventrolateral surfaces of the

centrum, below the lateral pneumatic fossa, converge on the ventral midline to form a very

prominent ‘basal ridge’ (modified from Blows 1995).

Discussion. Seeley (1870) included two vertebrae (NHMUK 28632 and R2239) in his

type series for Ornithopsis. These two specimens come from localities on the Isle of Wight

and Tilgate Forest, West Sussex, respectively, and NHMUK R2239 does not share any

diagnostic features with NHMUK 28632. Thus, there are no grounds for suggesting that

these two specimens belong to the same species: Lydekker (1888a) therefore restricted

the type material to NHMUK 28632, effectively designating it as the lectotype of O. hulkei

(see also Lydekker 1888b; Blows 1995). The lectotype is the centrum and part of the arch

of a dorsal vertebra. The centrum is compressed transversely so that it is taller than wide

(Text-fig. 13B). Ventrally, the centrum possesses ventrolaterally facing surfaces that meet

each other on the midline to form a sagittal ridge (the ‘basal ridge’ of Blows 1995). A

damaged area along the right ventrolateral margin of the anterior articular ‘ball’ reveals

that the internal tissue structure is comprised of relatively large camellae. On each lateral

surface, there is a rounded to subtriangular pneumatic fossa, with the parapophyses

probably located just above the fossa’s anterodorsal corner (Text-fig. 13A). There is no

dividing oblique lamina within this fossa. The centrum is opisthocoelous, with an anterior

articular ‘ball’ that is less prominent than those of typical sauropod cervicals, but more so

than typical sauropod dorsals. Collectively, these features (especially the position of the

parapophysis) suggests that this specimen is an anterior dorsal vertebra (perhaps number

three or four), rather than a posterior dorsal as proposed by Blows (1995).

The taxonomic and nomenclatural history of Ornithopsis is extremely complex.

Owen (1875) erected ‘Bothriospondylus magnus’ for the lectotype vertebra. This created a

junior objective synonym that has not been used by most subsequent workers (see also

Mannion 2010). Historically, numerous other specimens (e.g. two cervical vertebrae,

NHMUK R87 and R87a), many of which display no anatomical overlap with the lectotype,

were referred to Ornithopsis by workers such as Lydekker (1888a). Much of this material

was later referred to Pelorosaurus (as ‘P. armatus’ - also including Oplosaurus [Lydekker

1888b]) and then ‘Hoplosaurus’ (Lydekker 1889, 1890a, 1892, 1893), but in most cases

these judgements were not made on the basis of comparable material.

Blows (1995) considered Ornithopsis hulkei to be diagnosable on the basis of five

character states: (1) well-developed opisthocoely; (2) centrum vertically tall and narrow

transversely; (3) basal ridge present; (4) the lateral pneumatic fossa (‘pleurocoel’) extends

over the posterior two-thirds of the centrum near the base of the neural arch; (5) the

parapophyses are located high on the neural arch. However, Upchurch (1993) and Naish

and Martill (2001) suggested that this taxon is a nomen dubium. 2004). Nevertheless, the

tall narrow centrum and prominent ventral sagittal crest appear to be real features that

cannot be explained easily in terms of postmortem distortion. Therefore Ornithopsis can

be provisionally retained as a distinct taxon.

Blows (1995, 1998) and Naish and Martill (2001, 2007) suggested that O. hulkei is a

brachiosaurid (see also Pelorosaurus conybeari in McIntosh 1990a). However, Upchurch

et al. (2004) regarded Ornithopsis as a potentially distinct form within the basal

Titanosauriformes. The latter view is preferred here because of the absence of convincing

character data to support the more precise brachiosaurid identification (see also Naish

2010).

‘Ornithopsis eucamerotus’ Hulke, 1882

Text-Figure 14

Holotype. NHMUK R97, left pubis and right ischium (Naish and Martill 2001, fig. 8.12;

Text-fig. 14A, C). There are some doubts concerning the association of the pubis and

ischium (see below).

Referred material. NHMUK R97a, the proximal part of a left ischium (Text-fig. 14B).

Locality and horizon. Brighstone Bay, Isle of Wight. Wessex Formation (Barremian:

Rawson 2006).

Discussion. The type material (NHMUK R97) is a left pubis and right ischium, and the

referred specimen (NHMUK R97a) is a virtually identical partial left ischium (Text-fig. 14).

The pubis has sometimes been identified as a ‘right’ (e.g. Naish and Martill 2001), but this

is incorrect. The pubis lacks the hooked ambiens process that occurs in many diplodocids

and dicraeosaurids (McIntosh 1990b; Upchurch 1998). The obturator foramen is widely

open and subcircular. Distally, the pubis is strongly convex in lateral view and somewhat

compressed transversely. The proximal plate of the right ischium is artificially narrow

anteroposteriorly because it has lost virtually all of the margin that would have articulated

with the pubis, but the left ischium has a nearly complete pubic articulation. The iliac

peduncle of the ischium is very wide transversely at its articular end, but narrows markedly

in the central part of the acetabular margin. There is a prominent ridge on the medial

margin of the acetabulum on the section formed by the iliac peduncle. A weakly developed

longitudinal ridge and groove are present on the dorsolateral part of the proximal end of

the shaft, as occurs in most sauropodomorphs (Yates 2007). Near the base of the

proximal plate, the shaft is twisted so that the distal ends of the ischia would have coplanar

cross sectional long-axes, as occurs in macronarians and basal diplodocoids such as

Haplocanthosaurus priscus and rebbachisaurids (Upchurch 1998; Wilson and Sereno

1998).

Other material, including one of the type specimens of O. hulkei was referred to this

new species by Hulke (1882), whilst Lydekker (1888a) referred all this material back to O.

hulkei. None of these referrals can be supported at present on the basis of shared

diagnostic features. However, specimens such as the ‘Barnes High sauropod’, which

preserves both vertebral and girdle elements, offer an opportunity to test the validity of

such referrals in the future.

One problem with ‘O. eucamerotus’ is that there is some disagreement concerning

whether the type pubis and ischium were found in association. Hulke (1882) and Lydekker

(1888a) stated that these two elements belonged to the same individual, and Hulke (in

Anonymous 1882) indicated that they were found in the same block (see Naish and Martill

2001). Blows (1995), however, argued that there is no evidence from the information

recorded by Rev. W. Fox that the pubis and ischium were found together, and Blows also

noted differences in the preservation of these elements. In particular, the left pubis and

ischium are somewhat darker in coloration than the right ischium. On the other hand, the

left ischium and pubis can be articulated convincingly with articular surfaces that match

each other closely in terms of length and curvature.

‘O. eucamerotus’ was identified as a brachiosaurid by Naish and Martill (2001, p.

216) largely on the basis that the distal end of the pubis possesses a characteristic

rounded projection that is also seen in Giraffatitan. These authors also noted a feature in

the ischium which is consistent with the brachiosaurid identification: the length of the pubic

articulation is greater than the distance from the anterodorsal corner of this articulation to

the posterior margin of the ischial shaft, as occurs in other macronarians (see Salgado et

al. 1997). As noted above, the proximal plate of the right ischium has been artificially

truncated through loss of the pubic articular region: however, in the better preserved left

ischium, the pubic articulation is still longer than the anteroposterior width of the proximal

plate. Other proportions of ‘O. eucamerotus’ provide mixed support for its assignment to

Titanosauriformes. The ischium is only 80 percent of pubis length, and a similar relatively

reduced ischium occurs in many basal titanosauriforms and somphospondylans (Upchurch

et al. 2004). In contrast, the length of the ischial articulation of the pubis is estimated to be

28–35 percent of pubis length, whereas this is normally 45–50 percent in most

macronarians (Salgado et al. 1997). The accuracy of both of these proportions can be

questioned because the pubis:ischium length ratio assumes that the right ischium and left

pubis come from the same individual, and the ischial articulation length:pubis length ratio

depends on an estimate based on a damaged margin. Naish and Martill (2007) were

conservative in their identification, regarding ‘O. eucamerotus’ as an undiagnostic

titanosauriform of uncertain affinities. We provisionally support this view here pending the

discovery of new and more complete material.

‘Pleurocoelus valdensis’ Lydekker, 1889

Text-Figure 15

Type material. This species was based upon two teeth in the NHMUK collections, but

Lydekker (1889) did not provide specimen numbers or other identifying information, and

no description was offered. Naish and Martill (2001) argued that ‘P. valdensis’ should be

regarded as a nomen nudum because a type specimen cannot be identified based on

Lydekker (1889). In contrast, Ostrom (1970) and Galton (1981) stated that a single tooth

was the type specimen: this might be the tooth figured by Lydekker (1890a, p. 182), but

this cannot be confirmed as being correct. Although Lydekker (1890a) described and

figured ‘P. valdensis’ teeth, he did not provide any details concerning either specimen

numbers or provenance, although the potential type specimen appears to be one of those

teeth previously identified as Hylaeosaurus by Owen (1858).

Referred material. NHMUK R647, R647a, R739, R1898, 2310, 2329, R2528, R2694,

3325, 3534 (Text-fig. 15A-D), R4403 (Text-fig. 15E-H), R4404–4407, R4437-4438,

R10093-10100, 10830, 26034, 36488, R35354, 43172, numerous small teeth and tooth

crowns (Swinton 1962). Teeth similar to those from Sussex have also been recovered

from the Isle of Wight (Naish and Martill 2001, fig. 8.6), but see below for a discussion of

the validity of such referrals and the distribution of ‘Pleurocoelus’-like teeth. Other teeth

labelled as ‘P. valdensis’ include NHMUK R3453 and R3562, but these are ornithischian

teeth (Barrett and Upchurch 1995). Lydekker (1889, 1890a, b) also referred two dorsal

centra (NHMUK R1616, R1730) from Sussex and the Isle of Wight. However, as noted by

Naish and Martill (2001), the referral of these vertebrae cannot be supported because

there is no anatomical overlap with the potential type material. These two dorsal centra

should therefore be regarded as Sauropoda indet. (Naish and Martill 2001).

Locality and horizon. NHMUK 43172, 26034, 2310, 3325, 36488 Cuckfield, West

Sussex, Grinstead Clay Member of the Tunbridge Wells Sands Formation (Valanginian:

Rawson 2006). NHMUK R739, R2528, Brickyard, Silver Hill near Hastings and NHMUK

R4404, Battle, East Sussex, both Wadhurst Clay Formation (Valanginian: Rawson 2006).

NHMUK R4405, Cliff End, near Hastings, East Sussex, exact horizon unknown (Hastings

Beds Group: late Berriasian–Valanginian). NHMUK R4407, West Fairlight, Hastings, East

Sussex, Ashdown Sands Formation (late Berriasian–Valanginian: Rawson 2006). Other

unnumbered specimens have been noted from the Wessex Formation (Barremian) of the

Isle of Wight (Lydekker 1889; Naish and Martill 2001).

Discussion. The genus Pleurocoelus is based on material from the Early Cretaceous of

North America (Marsh 1888). Another North American taxon, Astrodon Johnston, 1859, is

based on a single tooth and is often considered to be a senior synonym of Pleurocoelus

(e.g. Steel 1970; Carpenter and Tidwell 2005): several authors (e.g. Swinton 1936;

Lapparent and Zbysewski 1957; Galton 1981) have therefore argued that ‘P. valdensis’

should be known as ‘Astrodon valdensis’. However, we consider Astrodon to be distinct

from Pleurocoelus, based on differences in tooth morphology, and therefore prefer the

name ‘P. valdensis’ for the English specimens

Lydekker (1889, 1890a) based ‘P. valdensis’ on teeth that had previously been

assigned to Hylaeosaurus by Owen (1858) and Lydekker (1888a: e.g. NHMUK R739 and

R2528). The following description applies to all specimens except NHMUK R4407,

R10100 and 43172 (see below). The teeth are small (crown lengths typically less than 15

mm; Text-fig 15). The root is usually subrectangular to subcircular in cross-section and has

fine longitudinal striations on its external surfaces. Crowns are slightly asymmetrical in

labial view, curving a little distally and lingually towards the apex. The labial surface is

strongly convex mesiodistally and vertically, and bears a pair of grooves extending parallel

to the mesial and distal margins, as occurs in most sauropods (Upchurch et al. 2004,

2007a, b). Generally, the lingual surface is very mildly concave. However, the small size of

the crown combines with the enlarged ridge that extends to the apex, to reduce the

relative size of the lingual concavity compared to that seen in the large spatulate teeth of

taxa such as Camarasaurus. As in other sauropods (Wilson and Sereno 1998), the crown

enamel is finely wrinkled. Some crowns (e.g. NHMUK R739, R4404) bear apical wear

facets, but wear on the mesial and distal margins is generally slight or absent. A few teeth

(NHMUK R4407, R10100 and 43172) are generally very similar to those described above,

but are more symmetrical in labial view and have a more prominent lingual ridge. As a

result of the latter, the crowns are elliptical rather than ‘D’-shaped in cross-section, with the

convexity of the lingual surface being nearly as marked as that of the labial surface.

Teeth closely resembling those of ‘P. valdensis’ are known from several other

localities globally. For example, teeth found in association with the Middle Jurassic

sauropod Lapparentosaurus madagascariensis (Ogier 1975; PU, pers. obs., 1992) are

nearly identical to those of ‘P valdensis’. Similar teeth are also known from the Late

Jurassic of Portugal and Early Cretaceous of North America (Marsh 1888; Lapparent and

Zbyszewski 1957; Galton 1981). No autapomorphies have been identified in any of these

teeth, and their geographic and stratigraphic ranges also suggest that it is unlikely that

they belong to a single genus or species. ‘P. valdensis’ should therefore be regarded as a

nomen dubium (contra Ruiz-Omeñaca and Canudo 2005). This means, of course, that

there is no justification for referring teeth from other localities in Sussex, the Isle of Wight,

or indeed elsewhere in the world, to ‘P. valdensis’, and this species cannot be confirmed

as congeneric with the type species Pleurocoelus nanus. Moreover, the two slightly

different crown shapes described above might indicate the presence of more than one

taxon among the ‘P. valdensis’ specimens (see also Lydekker 1890a, p. 183).

Naish and Martill (2001) identified ‘Pleurocoelus valdensis’ as an indeterminate

titanosauriform, citing the presence of the grooves on the labial surfaces of each crown in

support of this view. However, as Naish and Martill (2001) themselves note, these grooves

also occur in all other sauropods except some derived diplodocoids and titanosaurs

(Upchurch et al. 2004) and thus cannot be used to support titanosauriform affinities. Ruiz-

Omeñaca and Canudo (2005) argued that ‘P. valdensis’ was distinct from the North

American type species of Pleurocoelus (P. nanus) and identified the English species as a

brachiosaurid. The reduction of the lingual concavity, and the development of a more

precise tooth-to-tooth occlusion that produces apical wear facets, are both derived states

that occur in diplodocoids and titanosauriforms (Upchurch and Barrett 2000). Only

brachiosaurids and basal somphospondylans possess teeth that combine these derived

states with a crown shape that is still reminiscent of the plesiomorphic spatulate condition.

We therefore provisionally support Naish and Martill’s (2001) more conservative

identification of ‘P. valdensis’ as a basal titanosauriform, since it cannot be assigned

specifically to the Brachiosauridae.

Unnamed taxon, the ‘Barnes High sauropod’

Material. MIWG BP001, a partial postcranial skeleton including presacral vertebrae,

anterior caudal vertebrae, girdle and limb elements (Naish and Martill 2001, pl. 15).

Locality and horizon. Barnes High, Isle of Wight (Radley 1993; Radley and Hutt 1993).

Wessex Formation (Barremian: Rawson 2006).

Discussion. The Barnes High sauropod represents one of the most complete and

important sauropod specimens from the UK. Aside from providing insights into the

composition of Wealden Group sauropod faunas, this material has the potential to resolve

a number of taxonomic and nomenclatural problems. In particular, various Wealden taxa

named on the basis of isolated vertebrae or limb elements (e.g. Eucamerotus foxi,

Ornithopsis hulkei, ‘O. eucamerotus’, and Pelorosaurus conybeari) could be compared

with the Barnes High specimen in order to determine whether they belong to one or

several genera. Currently, the Barnes High specimen is in private hands and there has

been no opportunity to publish a detailed description of this material. Nevertheless, a few

observations on this material and its bearing on other Wealden sauropod taxa can be

made. For example, the anconeal fossa at the distal end of the posterior surface of the

humerus is apparently shallower in the Barnes High specimen than in Pelorosaurus

conybeari (Naish and Martill 2001), perhaps suggesting that each represents a distinct

taxon.

Blows (1995) referred the Barnes High specimen to Eucamerotus foxi on the basis

that the dorsal vertebrae of the former possess the autapomorphies observed in the

holotype of the latter. However, Naish and Martill (2001) and Upchurch et al. (2004)

questioned the validity of many of these autapomorphies (see above), and therefore cast

doubt on the referral of the Barnes High specimen to Eucamerotus. Moreover, D. Naish

(pers. comm.. 2011) has suggested that there are clear differences in the vertebral

anatomy of E. foxi and the Barnes High specimen that indicate that they are unlikely to be

conspecific or even congeneric. Naish and Martill (2001) agreed with Blows (1995) that the

Barnes High specimen should be regarded as a brachiosaurid. Here, we assign this

specimen to the Titanosauriformes, but do not place it within the Brachiosauridae (see the

discussion of the relationships of Eucamerotus above). The Barnes High animal probably

lies outside of Titanosauria and should therefore be regarded as a basal titanosauriform of

uncertain affinities, pending its inclusion in a phylogenetic analysis.

ENIGMATIC AND PROBLEMATIC WEALDEN SAUROPODS

Introduction

Many Wealden sauropod specimens can be identified as members of particular

neosauropod clades, such as Rebbachisauridae, Titanosauriformes, etc., even if their

precise affinities cannot be determined. However, there are some fragmentary specimens

which, despite possessing distinctive features that suggest that they represent valid taxa,

cannot be identified more precisely than Eusauropoda incertae sedis. Below, such

enigmatic specimens are discussed and their possible affinities are evaluated in the light

of the more recent information on character state distributions among sauropods.

Systematic palaeontology

SAUROPODA Marsh, 1878

EUSAUROPODA Upchurch, 1995

Incertae sedis

‘Chondrosteosaurus magnus’ Owen, 1876

Type material. NHMUK R98, a partial dorsal vertebra (Owen 1876, pl. 6).

Locality and horizon. Locality unknown, south coast of the Isle of Wight. Wessex

Formation (Barremian: Rawson 2006).

Discussion. Owen (1876) referred the type specimen of ‘Bothriospondylus magnus’

(NHMUK 28632, the lectotype of Ornithopsis hulkei, see above) and a water-worn centrum

from the Wealden of the Isle of Wight to ‘C. magnus’, but this cannot be justified on the

basis of any valid shared diagnostic features (Naish and Martill 2001, 2007). NHMUK R98

can be recognised as a dorsal vertebra of a sauropod, but generally lacks taxonomically

informative features. This taxon should therefore be regarded as a nomen dubium

(Upchurch 1993; Naish and Martill 2001, 2007; Upchurch et al. 2004).

Oplosaurus armatus Gervais, 1852

Text-figure 16

Type material. NHMUK R964, an isolated tooth crown and root (Wright 1852; Lydekker

1888a, 1888b, pl. 3, fig. 4, 1893; Naish and Martill 2001, figs 8.10–8.11; Text-fig. 16).

Locality and horizon. Brighstone (= ‘Brixton’) Bay, Isle of Wight. Wessex Formation

(Barremian: Rawson 2006).

Diagnosis. Oplosaurus possesses the following autapomorphies: (1) absence of a midline

ridge within the concavity on the lingual surface of the crown; (2) the grooves near the

mesial and distal edges of the labial crown surface are less well developed than in other

spatulate sauropod teeth; and (3) the mesial and distal portions of the labial crown surface

meet each other at an abrupt angle (approximately 90°) rather than merging smoothly into

each other (Upchurch et al. 2004).

Discussion. This isolated tooth has a spatulate crown with faint medial and distal grooves

on its labial surface and a deep concavity on its lingual surface (Text-fig. 16A, C). The

spatulate shape of this tooth, the presence of wrinkled enamel, and the concave lingual

surface, confirm that it belonged to a sauropod (Upchurch 1998; Wilson 2002; Upchurch et

al. 2004). Naish and Martill (2001, p. 212) stated that isolated sauropod teeth are generally

undiagnostic and therefore regarded Oplosaurus armatus as a nomen dubium. However,

Upchurch et al. (2004) noted several potential diagnostic features. Unlike all other

spatulate sauropod teeth, the lingual concavity does not display a distinct central ridge that

extends from root to apex: instead this area is smooth over its entire extent (Text-fig. 16C).

The crown is also unusual in being spatulate while simultaneously possessing very faint

labial grooves, and the mesial and distal portions of the labial surface meet each other at

nearly 90° to form an acute ridge near the apex of the tooth (Upchurch et al. 2004).

Oplosaurus is therefore provisionally regarded as a valid genus, although future

discoveries of more complete material might eventually render it a nomen dubium.

NHMUK R751 is a badly broken section of maxilla that bears a tooth that is

supposedly similar to that of Oplosaurus (Lydekker 1888b, pl. 3, figs 1–3; Naish and Martill

2001). Lydekker (1890a, b) also referred another tooth (NHMUK R1617) to ‘Hoplosaurus’

(=Oplosaurus, see below). Both of these referrals are dubious because the tooth crowns

do not possess the unique features observed in the type specimen of Oplosaurus.

Oplosaurus has been caught up in the complex network of synonymies and

referrals that have involved most named Wealden sauropods. It was referred to

Pelorosaurus by Owen (1884), and was combined with Ortnithopsis hulkei in the new

combination of ‘Pelorosaurus armatus’ by Lydekker (1889). Oplosaurus was also

considered to be congeneric with Onrithopsis by Lydekker (1888a, b, 1889, 1893).

Lydekker (1890a) misspelled the name as ‘Hoplosaurus’ armatus, and referred many of

the Pelorosaurus and Ornithopsis specimens to this taxon. This error persisted in later

literature (e.g. Lydekker 1892, 1893). Given that the type specimens of Pelorosaurus and

Ornithopsis are a humerus and a vertebra respectively, these referrals cannot be justified

at present.

The phylogenetic affinities of Oplosaurus are controversial. Naish and Martill (2001)

suggested that Oplosaurus is a brachiosaurid, whereas Canudo et al. (2002) and

Sanchez-Hernandez et al. (2007) proposed that it is a camarasaurid. Although

brachiosaurids and Camarasaurus have large spatulate teeth, there are difficulties with

both of these identifications: neither taxon possesses clear derived character states

relating to dental morphology that could justify the referral of Oplosaurus. For example,

Canudo et al. (2002, p. 449) argued that the Oplosaurus tooth crown lacks the ‘conical’

shape typical of brachiosaurids but was similar to the condition observed in Camarasaurus

(but no specific characters were listed). The Slenderness Index (i.e. the height of tooth

crown divided by its mesiodistal width: Upchurch 1998) is 1.84 in Oplosaurus. In broad-

crowned non-neosauropods this value ranges from 1.36 in Jobaria to 2.42 in

Mamenchisaurus, and in Camarasaurus the SI has an average value of 1.92 (Chure et al.

2010). In most titanosaurs and diplodocoids the SI value is much greater (3.0–6.0 in the

former and 4.0–5.5 in the latter) and in brachiosaurids and basal titanosauriforms it is 2.3–

3.5 (Chure et al. 2010). Thus, the SI value of Oplosaurus lies in the range expected for

Camarasaurus-like animals and non-neosauropods generally. However, tooth proportions

can vary along the jaw of a single individual and also seem relatively plastic in evolutionary

terms, so caution should be exercised when using SI values to identify isolated teeth.

Upchurch et al. (2004) listed Oplosaurus as Sauropoda incertae sedis, but the available

character data suggest that it can safely be regarded as at least belonging to

Eusauropoda.

Unnamed taxon, ‘the Brook sauropod’

Material. NHMUK 36559, a posterior ‘dorsal’ vertebra and the attached anterior half of a

sacral vertebra; NHMUK 36559a, partial second and third sacral vertebrae; NHMUK

36559b, partial third sacral vertebra; NHMUK 28640, fourth sacral vertebra; NHMUK

36559c, anterior caudal vertebra; NHMUK 36559d, posterior dorsal vertebra; NHMUK

36559e, two metatarsals and four phalanges; NHMUK 27500, a distal caudal vertebra,

chevron and fragmentary pubis and ischium; NHMUK R206, limb bones, five metatarsals

and four phalanges (Lydekker 1888a; Naish and Martill 2001, p. 236).

Locality and horizon. Brook, Isle of Wight. Wessex Formation (Barremian: Rawson

2006).

Discussion. The NHMUK specimens listed above were originally referred to ‘Cetiosaurus

brevis’ (Lydekker 1888a) and later to ‘Morosaurus brevis’ (Lydekker 1892). Lydekker

(1888a, 1892) believed that NHMUK 36559a-e, 28640, 27500 and R206 belonged to a

single individual. However, as noted by Naish and Martill (2001, p. 236), many 19th

Century palaeontologists, such as Lydekker, were more willing to make assumptions that

separate specimens belong to the same taxon, or even the same individual, than their

twenty-first century counterparts. For example, Lydekker’s criteria for grouping specimens

together as single taxa or individuals often relied on doubtful evidence such as their

recovery from the same locality, or similarities in preservation style and size. Many of

these NHMUK specimens are fragmentary and the extent to which they were found in

association is unclear. However, these specimens deserve further study because

opportunities to examine potentially associated sauropod remains from the Wealden of the

United Kingdom are extremely rare. We provisionally regard these Brook specimens as

Sauropoda indet., although further study should provide data that will support a more

precise identification.

Unnamed taxon, ‘the Smokejacks sauropod’

Material. NHMUK unnumbered specimen, right humerus; NHMUK R6622, left femur. Both

specimens belong to the Rivett Collection (Rivett 1953, 1956).

Locality and horizon. Smokejacks Brickworks, Ockley, Surrey. Upper Weald Clay

Formation, Weald Clay Group (late Barremian–early Aptian: Rawson 2006).

Discussion. The unnumbered right humerus is complete but has suffered some crushing.

In anterior view, the proximal articular surface and lateral margin merge smoothly into

each other, rather than meeting at a more abrupt right-angle as occurs in many

titanosauriforms, especially titanosaurs (Upchurch 1998; Upchurch et al. 2004; Mannion

and Calvo in press). The deltopectoral crest is not well preserved, but this structure

appears to terminate well above the mid-length of the humerus. As in most sauropods, the

mid-shaft region is anteroposteriorly compressed. The distal articular surface is flat and

does not curve up onto the anterior face of the shaft, unlike the humeri of advanced

titanosaurs (Wilson and Carrano 1999). NHMUK R6622 is a well-preserved left femur. It

displays all of the features that typically occur in a sauropod femur, such as the absence of

the lesser trochanter, reduced fourth trochanter, and long straight shaft that is compressed

anteroposteriorly. This specimen retains a number of plesiomorphic (=’primitive’) character

states that suggest that it does not belong to a titanosaur or even a titanosauriform. For

example, the proximal third of the femur is not deflected medially, and the striated ‘bulge’

on the lateral surface of the shaft (near the proximal end) is relatively small (Salgado et al.

1997; Upchurch 1998; Wilson and Sereno 1998). Moreover, in titanosaurs the fibular

condyle projects slightly further distally than does the tibial condyle (Wilson and Carrano

1999). However, in R6622, the tibial condyle projects further than the fibular one. Finally,

in advanced titanosaurs such as saltasaurines, the distal articular surface curves up onto

the anterior face of the shaft, whereas in R6622 this surface faces mainly distally.

Benton and Spencer (1995) listed these specimens as ‘Titanosauridae indet.’ and

Weishampel et al. (2004) classified them as ‘Lithostrotia indet’. Although the unnumbered

humerus and R6622 were found at the same locality and are similar in size, there is no

compelling evidence to suggest that they belong to the same individual or even the same

taxon. Both specimens, however, display features that are consistent with them belonging

to a non-titanosauriform (or only a very basal titanosauriform). Pending further study, we

provisionally regard these Rivett collection specimens as Eusauropoda indet.

SAUROPOD FOOTPRINTS

Sauropods were quadrupedal and produced distinctive trackways that combine crescentic,

horseshoe-shaped handprints (created by the tightly bound tubular arrangement of the

metacarpals) with much larger, subcircular or subovate footprints, which may show

evidence of individual digits and/or claw impressions (up to three claws representing digits

I–III: however, preservation is rarely good enough to capture these features). Footprints

can be of extremely large size (commonly 40–70 cm in diameter). This combination of

features is not seen in any other dinosaur group, but isolated footprints can be difficult to

distinguish from those of other large quadrupedal dinosaurs, such as ankylosaurs (see

Lockley [1990] for an overview of dinosaur footprint types).

Sauropod tracks have been reported from Wealden Supergroup sediments, with

several possible examples noted from the Wessex Formation of the Isle of Wight,

occurring on the foreshore at Yaverland and at Brook Bay (Radley 1994a, b; Goldring et

al. 2005, fig. 5F). However, it should be noted that these isolated tracks, which are not

associated with either crescentic handprints or distinct claw impressions, might have been

produced by an ankylosaur (Radley 1994a, b; Goldring et al. 2005). Unconfirmed reports

of sauropod tracks from the mainland Weald have also been mentioned (Wright et al.

1998; D. D. Scarboro, pers. comm., 2006), but none of these occurrences has been

formally described or evaluated to date.

CONCLUSION

Sauropod remains are known from the Wealden of East and West Sussex, Surrey, and the

Isle of Wight, but not Dorset (contra Weishampel et al. 2004: see Barrett et al. 2010). Two

issues have dominated recent work on Wealden sauropods. First, workers have argued

that the diagnoses of most or all named taxa are inadequate, so that nearly every genus

and species is considered to be a nomen dubium (e.g. Naish and Martill 2001, 2007:

Upchurch et al. 2004). Certainly most type specimens would be considered inadequate by

modern taxonomic standards and might not be named if they were discovered now.

However, the tendency to regard most taxa as indeterminate is perhaps overly pessimistic.

The generation of increasingly detailed phylogenetic data sets has produced a wealth of

comparative data and enabled potential autapomorphies, or at least unusual combinations

of character states, to be recognised. Here we provisionally accept the validity of five

genera and species including Pelorosaurus conybeari and Xenoposeidon proneneukos

from the Hastings Subgroup of Sussex and Eucamerotus foxi, Ornithopsis hulkei and

Oplosaurus armatus from the Wessex Formation of the Isle of Wight. Moreover, unnamed,

or incorrectly named forms, such as ‘Pelorosaurus becklesii’, the ‘Barnes High sauropod’

and the Isle of Wight rebbachisaurid, indicate the potential for recognising several new

forms in the future.

The second issue is that most authors (e.g. Blows 1995, 1998; Naish and Martill

2001, 2007; Taylor and Naish 2007) have tended to place Wealden sauropods in the

Brachiosauridae, when in fact the evidence for this is either ambiguous or contradictory.

Certainly forms such as Pelorosaurus conybeari, Eucamerotus foxi, Ornithopsis hulkei and

the ‘Barnes High sauropod’ seem to be basal titanosauriforms: however, whether they

belong in the Brachiosauridae oar are more closely related to somphospondylans cannot

be fully determined until more data are available on both the anatomy of these Wealden

forms and the relationships of basal titanosauriforms.

This review of Wealden sauropods suggests subtle, but potentially important,

changes to our understanding of the Early Cretaceous sauropod faunas of the UK. Taylor

and Naish (2007) suggested that the higher-level diversity of the Hastings Beds Group of

Sussex was probably similar to that seen in the later Wessex Formation of the Isle of

Wight. They envisaged that the Hastings Beds Group fauna included a diplodocid, a basal

titanosauriform (Pelorosaurus conybeari), a titanosaur (‘Pelorosaurus becklesii’) and

perhaps a new clade represented by Xenoposeidon. Here, however, we have substantially

reduced this diversity because the diplodocid metacarpal from Bexhill beach can only be

identified as Sauropoda indet. (Upchurch and Mannion 2009), and we regard

Xenoposeidon as a probable basal titanosauriform or somphospondylan. Thus, the late

Berriasian to Valanginian-aged Hastings Beds Group is dominated exclusively by

titanosauriforms at present, although this might be overturned by future discoveries.

By contrast, the Wessex Formation seems to have been more diverse than

proposed by recent studies. Blows (1995, 1998) recognised a relatively limited diversity of

sauropod taxa in the Wessex Formation, including several brachiosaurids, a diplodocid

and one titanosaur. Similarly, Naish and Martill (2001, p. 188) argued that the proliferation

of names, based on inadequate type material, has led to a false impression of high

sauropod diversity. These authors suggested that in fact sauropod diversity was probably

quite low because of the limits on carrying capacity imposed by large body size. Naish and

Martill (2001) therefore suggested that the Isle of Wight sauropod fauna included a

diplodocid, a brachiosaurid, a titanosaur and possibly a camarasaurid. Here, however, we

argue that this fauna had a slightly different composition and was substantially more

diverse. At present, there is evidence for the occurrence of a rebbachisaurid, a true

brachiosaurid, at least one basal titanosauriform that might be closer to Somphospondyli

than to Brachiosauridae, two distinct advanced titanosaurs, a possible non-titanosauriform

macronarian or even a non-neosauropod (Oplosaurus armatus) and the forked chevron

(NHMUK R8924) that represents either a flagellicaudatan or a non-neosauropod

eusauropod. Thus, a conservative estimate of the diversity of the Isle of Wight sauropod

fauna would be a minimum of six distinct genera.

Several of the above identifications are significant at a global scale. In particular,

the possibility that the Early Cretaceous of the UK included a flagellicaudatan would be

surprising given the current view that diplodocids became extinct at the

Jurassic/Cretaceous boundary (but see Upchurch and Mannion 2009), and that

dicraeosaurids were restricted to South America at this time. Similarly, broad tooth-

crowned non-neosauropod eusauropods also suffered extinctions at the

Jurassic/Cretaceous boundary (Barrett and Upchurch 2005; Upchurch and Barrett 2005;

Chure et al. 2010; Mannion et al. 2011), and such forms are generally rare in the Early

Cretaceous. Yet the Isle of Wight fauna suggest that some non-neosauropods, or basal

broad tooth-crowned macronarians might be present.

In summary, Wealden sauropod faunas are frustrating because of fragmentary

specimens and the associated confused taxonomy. Nevertheless, these specimens are

important because of the insights they yield into the nature of Early Cretaceous sauropod

faunas during the transition from the broad tooth-crowned eusauropod and

flagellicaudatan assemblages that typify the Late Jurassic to the rebbachisaurid and

titanosaur dominated faunas of the Late Cretaceous. Thus, future discoveries of Wealden

material offer important opportunities for the UK’s fossil record to contribute to our

understanding of sauropod evolutionary history at a global scale.

Acknowledgements. We thank Steve Hutt (MIWG) and Sandra Chapman (NHMUK) for

facilitating access to specimens in their care. The photographs in Text-figures 6-16 were

provided by Phil Hurst of NHMUK Image Resources. Finally, we are grateful to Darren

Naish, who reviewed an earlier version of the manuscript and made valuable suggestions

for improvements.

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Figure captions

Text-Figure 1. Skeletal reconstructions of sauropod dinosaurs. A, Shunosaurus (a basal

eusauropod), B, Apatosaurus (a diplodocid), C, Nigersaurus (a rebbachisaurid), and

D, Giraffatitan (a basal titanosauriform). Scale bars = 2 m. Images A, B and D,

modified from Upchurch et al. (2004), and C modified from Sereno et al. (2007).

Text-Figure 2. Sauropod skulls in left lateral view. A, Shunosaurus (a basal eusauropod),

B, Diplodocus (a diplodocid), C, Nigersaurus (a rebbachisaurid), D, Camarasaurus

(a basal macronarian), E, Giraffatitan (a basal titanosauriform), and F,

Rapetosaurus (a titanosaur)(. Scale bars = 100 mm. Images are modified from

Upchurch et al. (2004) (A, B, D and E), Sereno et al. (2007) (C), and Curry Rogers

and Forster (2001) (F).

Text-Figure 3. A simplified cladogram of sauropod evolutionary relationships (taken from

Mannion et al. 2011).

Text-Figure 4. Sauropod axial elements (A-D Giraffatitan; E-H, Dicraeosaurus). A, middle

cervical vertebra in right lateral view, B, middle-posterior cervical vertebra in

posterior view, C, middle-posterior dorsal vertebra in posterior view, D, anterior

caudal vertebra in right lateral view, E, anterior caudal vertebra in left lateral view,

F, same specimen as E in anterior view, G, forked chevron in lateral view, and H,

same specimen as G in proximal view. Elements are not drawn to scale. Images

after Janensch (1929, 1950).

Text-Figure 5. Sauropod appendicular elements (A-I, Giraffatitan; J, Dicraeosaurus; K and

L, ?Tornieria). A, proximal view of right ulna and radius, B, right ulna in anterior

view, C, right radius in anterior view, D, right manus in proximal view, E, right

manus in anterior view; F, right ilium in lateral view, G, right femur in posterior view,

H, right tibia in proximal view, I, right tibia in anterior view, J, left astragalus in

posterodorsal view, K, left metatarsals in proximal view, and L, left metatarsals in

dorsal view. Elements are not drawn to scale. Images after Janensch (1961).

Text-Figure 6. A partial left scapula of a rebbachisaurid sauropod (MIWG 6544) from

Brighstone Bay, Wessex Formation, Isle of Wight (from Mannion 2009). The

scapula is shown in lateral view with its broken and strongly expanded distal end

located at the right side of the figure. The ‘hook’-like process of the acromial

expansion can be seen at the top left. Scale bar = 10 cm.

Text-Figure 7. Part of the syntype material of Pelorosaurus conybeari from Tilgate Forest,

Cuckfield, West Sussex. Caudal vertebra (NHMUK R2544) in A, anterior, B, right

lateral, and C, posterior views. Caudal vertebra (NHMUK R2545) in D, anterior, E,

right lateral, and F, posterior views. Anterior haemal arch (chevron) in G, posterior

view. Scale bars = 20 cm (A-F) and 5 cm (G).

Text-Figure 8. Left humerus of ‘Pelorosaurus becklesii’ (NHMUK R1870) from Hastings,

East Sussex. A, anterior, B, left lateral, C, proximal end, D, distal end views (N.B.

the anterior surfaces of the proximal and distal ends face towards the top of the

figure). Scale bars = 20 cm.

Text-Figure 9. A skin impression (NHMUK R1868) apparently found in association with the

left fore limb of ‘Pelorosaurus becklesii’, from Hastings, East Sussex. Scale bar =

20 cm.

Text-Figure 10. Left lateral view of middle caudal vertebrae of an unnamed titanosaurian

sauropod (NHMUK R5333) from Brook, Isle of Wight. Scale bar = 20 cm.

Text-Figure 11. The holotype of Eucamerotus foxi (NHMUK R2522) from Brook, Isle of

Wight. Dorsal neural arch in A, anterior, B, posterior, and C, left lateral views.

Abbreviations: pp, parapophysis; pr-pp f, fossa created by two sub-horizontal

laminae that link the prezygapophysis to the parapophysis. Scale bars = 20 cm.

Text-Figure 12. One of the paratype dorsal vertebrae (NHMUK R89) of Eucamerotus foxi

from Brook Bay, Isle of Wight. A, left lateral, and B, right lateral views. Scale bar =

18 cm.

Text-Figure 13. The lectotype of Ornithopsis hulkei (NHMUK 28632) from Brook Bay,

Wessex Formation, Isle of Wight. This is the centrum and base of the neural arch of

an anterior dorsal vertebra in: A, left lateral view; B, anterior view. Scale bars = 20

cm.

Text-Figure 14. ‘Ornithopsis eucamerotus’ from Brighstone Bay, Isle of Wight. A, the

holotypic left pubis (NHMUK R97) in medial view, B, referred partial left ischium

(NHMUK R97a) in medial view, C, the holotypic right ischium (NHMUK R97) in

lateral view. Scale bars = 20 cm.

Text-Figure 15. Teeth of ‘Pleurocoelus valdensis’ from localities near Hastings, East

Sussex. NHMUK 3534 in A, labial, B, distal(?), C, lingual, and D, apical views.

NHMUK R4403 in E, labial, F, distal(?), G, lingual, and H, apical views. Scale bars

= 10 mm.

Text-Figure 16. The holotype of Oplosaurus armatus (NHMUK R964) from Brixton Bay,

Isle of Wight. Tooth crown and root in A, labial, B, mesial(?), C, lingual, and D,

apical views. Scale bars = 5 cm (A-C) and 2 cm (D).

Table 1. Summary of sauropod specimens found in the Wealden Group of the United

Kingdom. The table is organised as an alphabetical list of localities.

Locality

County

Geological unit

Sauropod

specimens/taxa

Barnes High

Isle of Wight

Wessex

Formation

Partial skeleton

Battle

East Sussex

Wadhurst Clay

Formation,

Weald Clay

Group

‘Pleurocoelus valdensis’

(titanosauriform teeth)

Bexhill beach

East Sussex

Hastings Beds

Sauropoda indet.

Group

(metacarpal)

Brighstone (=

‘Brixton’ in older

literature) Bay

Isle of Wight

Wessex

Formation

Oplosaurus armatus

(tooth); ‘Ornithopsis

eucamerotus’ (pubis

and ischia);

Rebbachisauridae indet.

(teeth, anterior caudal

neural arch and spine,

scapula); Titanosauria

indet. (left humerus);

Titanosauriformes indet.

(caudal vertebrae, other

vertebrae); Sauropoda

indet. (cervical, sacral,

caudal vertebrae,

miscellaneous other

vertebrae, rib, scapula,

humerus, ischium, 2

femora, tibia and 2

fibulae)

Brook Bay

Isle of Wight

Wessex

Formation

Eucamerotus foxi

(dorsal neural arch);

‘Iuticosaurus valdensis’

(caudal vertebrae);

Titanosauria indet.

(caudal vertebrae);

Sauropoda indet.

(femur, and also a

dorsal vertebra

previously assigned to

‘Pleurocoelus

valdensis’)

Chilton

Isle of Wight

Wessex

Formation

Ornithopsis hulkei

(dorsal vertebra)

Compton Bay

Isle of Wight

Wessex

Formation

Titanosauriformes indet.

(tooth); Sauropoda

indet. (tooth, cervical

vertebra, caudal

vertebra, metacarpal IV)

Cuckfield

(Tilgate Forest)

West Sussex

Grinstead Clay

Member,

Tunbridge

Wells Sands

Formation,

Hastings Beds

Group

Pelorosaurus conybeari

(humerus, anterior

caudal vertebrae and

chevrons, possibly three

middle caudal

vertebrae);

‘Pleurocoelus valdensis’

(teeth); Sauropoda

indet. (dorsal vertebra

previously assigned to

‘Pleurocoelus

valdensis’)

Ecclesbourne

East Sussex

Ashdown

Xenoposeidon

Glen

Formation,

Hastings Beds

Group

proneneukos (dorsal

vertebra)

Grange Chine

Isle of Wight

Wessex

Formation

Eusauropoda indet.

(forked chevron)

Hastings

East Sussex

Hastings Beds

Group

‘Pelorosaurus becklesii’

(forelimb, skin

impression)

Hastings (Cliff

End and Silver

Hill)

East Sussex

Weald Clay

Group

‘Pleurocoelus valdensis’

(titanosauriform teeth)

Hastings

(Fairlight West)

East Sussex

Ashdown

Sands

Formation

‘Pleurocoelus valdensis’

(titanosauriform teeth)

Sandown Bay

Isle of Wight

Wessex

Formation

Sauropoda indet.

(caudal vertebra, ungual

phalanx)

Smokejacks

Brickworks

Surrey

Upper Weald

Clay Formation

Sauropoda indet.

(*humerus and femur)

Sudmore Point-

Chilton Chine

Isle of Wight

Wessex

Formation

Brachiosauridae indet.

(cervical vertebra)

Sussex locality

Essex

Weald Clay

Group

Sauropoda indet.

(dorsal vertebra)

Isle of Wight

Wessex

Formation

Eucamerotus foxi

(several dorsal

vertebrae)

? (South coast)

Isle of Wight

Wessex

Formation

‘Chondrosteosaurus

magnus’ (dorsal

vertebra);

‘Chondrosteosaurus

gigas’ (titanosauriform

cervical vertebra)

Kent

?Hastings Beds

Group

‘Ornithopsis sp.’

(Weishampel et al.

2004)

New remains from the Spanish Cenomanian shed light on the Gondwanan origin of European Early Cretaceous titanosaurs

Article

Oct 2018

Algora is a recently discovered vertebrate fossil site located in the Cenomanian strata of the Arenas de Utrillas Formation (Guadalajara, Central Spain). This fossil site is rich in turtle remains, but other clades of reptiles are also identified, including plesiosaurs, crocodyliforms and dinosaurs. The only remains of dinosaurs from Algora so far studied corresponded to theropod teeth. However, several sauropod remains are here presented and analyzed, revealing the presence of several shared features with members of Titanosauriformes, some common found in derived members belonging to Lithostrotia clade. This sauropod fossil assemblage corresponds to the richest sauropod fossil accumulation found in the Cenomanian of Europe. In addition, one of the first studies of the pneumatic features in dorsal ribs using CT scan is also provided here. The performed cladistic analysis places the Algora sauropod within Lithostrotia, in a more derived position than Malawisaurus (supported, for example, by the presence of convex posterior articulation up to the posterior section of the tail), in a clade which also includes Rapetosaurus (Maastrichtian, Madagascar) and the Italian indeterminate titanosaur MSNM V7157 (late Aptian–early Albian). The Algora titanosaur and MSNM V7157 are recognized as closely related. This analysis shows the presence of two different lineages (Algora titanosaur + MSNM V7157 and Normanniasaurus, from the Albian of France) in the Early and middle Cretaceous of Europe, and at least one with a Gondwanan origin. The close relationship of the Algora titanosaur and MSNM V7157 suggests a pre-late Aptian faunal contact between the Adriatic Plate and Laurasia, in accordance with several previous studies, which proposed faunal exchanges between Laurasia and Gondwana through the Adriatic plate during the Early Cretaceous.

Charles Dawson and his List of Wealden Fossils

Article

Full-text available

Dec 2012

This article looks at the palaeontological activities of Charles Dawson, and also his ‘List of Wealden and Purbeck-Wealden fossils’, published by the Brighton and Hove Natural History anf Philosophical Society in 1898. Reference: Brook, A., Austen, P.A. 2012. Charles Dawson and his List of Wealden Fossils. Hastings & District Geological Society Journal, 18, 38–50. [Part 1 – Charles Dawson as Wealden Fossilist by Anthony Brook. Part 2 – The Fossils by Peter Austen]

Hastings & District Geological Society Journal [2012]

Book

Full-text available

Dec 2012

Hastings & District Geological Society Journal, Vol.18, December 2012 (Low Resolution) CONTENTS: 2012 Officials and Committee . . . p.1 // Minutes of the AGM – 11th December 2011 . . . p.2 // Statement of Income & Expenditure and Balances for the Year Ending 31st December 2011 . . . p.5 // New fossils from a classic area: the Builth Inlier - by Tess Ormrod . . . p.6 // A ‘Society’ Wedding - May 2012 . . . p.16 // Dinosaur Quarries of Hastings: Shornden Quarry - an update - by Ken Brooks . . . p.17 // Collecting minerals in the Eifel Mountains - by Trevor Devon . . . p.20 // The stunning Glacier Gardens of Lucerne - by Geoff Bennett . . . p.22 // Life and death in Cretaceous seas - by Andy Ottaway . . . p.24 // Geologists’ Association Field Meetings - 2013 . . . p.25 // Sussex Mineral & Lapidary Society celebrates 40th Anniversary - by Trevor Devon . . . p.26 // HDGS visit to the Sussex Mineral Show, Haywards Heath - November 2012 . . . p.27 // Fairlight Cove field meeting, 6th May 2012 - by Alison Nicholls (Oxford Geology Group) . . . p.28 // Geologists’ Association Festival of Geology, UCL, London - November 2012 . . . p.31 // HDGS Barbecue - August 2012 . . . p.32 // HDGS field trip to Cooden, near Bexhill, East Sussex, 1st July 2012 - by Peter and Joyce Austen . . . p.33 // Charles Dawson and his List of Wealden Fossils - by Anthony Brook and Peter Austen . . . p.38 // Geology and Palaeontology in the News - edited by Peter Austen . . . p.50 // Websites - by Peter Austen . . . p.57 //

New sauropod dinosaur from the Lower Cretaceous of Morella (Spain) provides new insights on the evolutionary history of Iberian somphospondylan titanosauriforms

Article

Sep 2023
ZOOL J LINN SOC-LOND

A new somphospondylan titanosauriform from the Lower Cretaceous of Spain is described from the remains found at the Sant Antoni de la Vespa site (upper Barremian Arcillas de Morella Formation) located in Morella. Garumbatitan morellensis gen. et sp. nov. is diagnosed by 11 autapomorphies and eight local autapomorphies; and our phylogenetic analyses suggest that Garumbatitan morellensis might correspond to an early-branching somphospondylan. The presence of several somphospondylan traits in Garumbatitan morellensis supports the somphospondylan hypothesis. The phylogenetic distribution of some titanosauriform and somphospondylan novelties in the femur (markedly developed lateral bulge, high shaft eccentricity, linea intermuscularis cranialis, and trochanteric shelf) is discussed. The tarsus and pes of Garumbatitan morellensis are distinctive, being characterized by the loss of the calcaneum, relative slenderness of the metatarsals II, III, and IV when compared to the retracted metatarsals I and V, three pedal phalanges in digit IV, and reduced ungual III. The sauropod fauna of the Iberian Peninsula during the Hauterivian–Aptian shows a complex phylogenetic mosaic, including forms with Laurasian affinities, mainly titanosauriforms (Soriatitan, Garumbatitan, and possibly Tastavinsaurus and Europatitan), and Gondwanan affinities, the rebbachisaurid Demandasaurus. Faunal exchange during the Early Cretaceous between the Europe, North America, East Asia, and Africa is plausible.

Sauropod dinosaur teeth from the lower Upper Cretaceous Winton Formation of Queensland, Australia and the global record of early titanosauriforms

Article

Full-text available

Jul 2022

The Upper Cretaceous Winton Formation of Queensland, Australia, has produced several partial sauropod skeletons, but cranial remains—including teeth—remain rare. Herein, we present the first description of sauropod teeth from this formation, based on specimens from three separate sites. An isolated tooth and a dentary fragment from the Diamantinasaurus matildae type locality are considered to be referable to that titanosaurian taxon. A single tooth from the D. matildae referred specimen site is similarly regarded as being part of that individual. Seventeen teeth from a new site that are morphologically uniform, and similar to the teeth from the two Diamantinasaurus sites, are assigned to Diamantinasauria. All sauropod teeth recovered from the Winton Formation to date are compressed-cone-chisel-shaped, have low slenderness index values (2.00–2.88), are lingually curved at their apices, mesiodistally convex on their lingual surfaces, and lack prominent carinae and denticles. They are markedly different from the chisel-like teeth of derived titanosaurs, more closely resembling the teeth of early branching members of the titanosauriform radiation. This provides further support for a ‘basal’ titanosaurian position for Diamantinasauria. Scanning electron microscope microwear analysis of the wear facets of several teeth reveals more scratches than pits, implying that diamantinasaurians were mid-height (1–10 m) feeders. With a view to assessing the spatio-temporal distribution of sauropod tooth morphotypes before and after deposition of the Winton Formation, we provide a comprehensive continent-by-continent review of the early titanosauriform global record (Early to early Late Cretaceous). This indicates that throughout the Early–early Late Cretaceous, sauropod faunas transitioned from being quite diverse at higher phylogenetic levels and encompassing a range of tooth morphologies at the start of the Berriasian, to faunas comprising solely titanosaurs with limited dental variability by the end-Turonian. Furthermore, this review highlights the different ways in which this transition unfolded on each continent, including the earliest records of titanosaurs with narrow-crowned teeth on each continent.

Dinosaur material from the Lower Greensand Group of Upware, Cambridgeshire, and the age of ‘Wealden’ vertebrates from the ‘Bedfordshire Straits’

Article

Jun 2021
P GEOLOGIST ASSOC

Paul M. Barrett

Post-Wealden dinosaur remains are rare in the UK, so any material from late Early or Late Cretaceous deposits is potentially of palaeoecological and palaeobiogeographical significance. Four dinosaur specimens collected from the Woburn Sands Formation (Aptian) of Upware, Cambridgeshire were described briefly by Walter Keeping in 1883, but have not been reappraised since. These specimens are identified herein as a ?turiasaurian sauropod tooth and indeterminate iguanodontian ornithopod remains (a tooth, middle caudal vertebra, pollex ungual). Although collected from the Woburn Sands Formation, it is likely that all of these fossils were reworked from older (now absent) sediments and they have usually been regarded as either ‘Wealden’ or Neocomian in age, presumably due to previous identifications of some of these specimens as Iguanodon. However, consideration of UK dinosaur faunas and regional geology indicates that these fossils could potentially be older. Further work is needed on the derived terrestrial fossils of the Lower Greensand Group in order to constrain their ages more precisely so that they can be incorporated into broader studies of regional diversity and palaeoecology.

First salamander from the Lower Cretaceous of Germany

Article

Aug 2020

A new salamandroid salamander, Balveherpeton hoennetalensis gen. et sp. nov., from the Lower Cretaceous (Barremian– Aptian) Balve locality in the Sauerland, Germany, is described on the basis of fragmentary atlases, trunk and caudal vertebrae. Balveherpeton hoennetalensis gen. et sp. nov. is characterized by the following combination of vertebral characters: prominent intercotylar tubercle; flat anterior cotylar surfaces on atlas; dorsoventrally compressed anterior cotyles of atlas; anterior cotylar surfaces on atlas continuous across lateral and ventral surfaces of intercotylar tubercle; deeply amphicoelous trunk vertebrae; low neural arch with low neural crest on trunk vertebra; bifurcate posterior part of the neural spine on trunk vertebrae; elongate depression on the posterior surface of the neural arch of trunk vertebrae; anterior basapophyses on trunk vertebrae; and posterior basapophyses on some trunk vertebrae. The phylogenetic position Balveherpeton hoennetalensis gen. et sp. nov. within the Salamandroidea is uncertain, but similarities in the structure of atlases and trunk vertebrae of Balveherpeton hoennetalensis gen. et sp. nov. and Wealden salamanders (e.g. “Keymer salamander”) could indicate a close relationship and provide additional evidence that the Early Cretaceous vertebrate faunas of Western Europe had similar compositions.

New information on the Cretaceous sauropod dinosaurs of Zhejiang Province, China: impact on Laurasian titanosauriform phylogeny and biogeography

Article

Full-text available

Aug 2019

Titanosaurs were a globally distributed clade of Cretaceous sauropods. Historically regarded as a primarily Gondwanan radiation, there is a growing number of Eurasian taxa, with several putative titanosaurs contemporaneous with, or even pre-dating, the oldest known Southern Hemisphere remains. The early Late Cretaceous Jinhua Formation, in Zhejiang Province, China, has yielded two putative titanosaurs, Jiangshanosaurus lixianensis and Dongyangosaurus sinensis. Here, we provide a detailed re-description and diagnosis of Jiangshanosaurus, as well as new anatomical information on Dongyangosaurus. Previously, a 'derived' titanosaurian placement for Jiangshanosaurus was primarily based on the presence of procoelous anterior caudal centra. We show that this taxon had amphicoelous anterior-middle caudal centra. Its only titanosaurian synapomorphy is that the dorsal margins of the scapula and coracoid are approximately level with one another. Dongyangosaurus can clearly be differentiated from Jiangshanosaurus, and displays features that indicate a closer relationship to the titanosaur radiation. Revised scores for both taxa are incorporated into an expanded phylogenetic data matrix, comprising 124 taxa scored for 548 characters. Under equal weights parsimony, Jiangshanosaurus is recovered as a member of the non-titanosaurian East Asian somphospondylan clade Euhelopodidae, and Dongyangosaurus lies just outside of Titanosauria. However, when extended implied weighting is applied, both taxa are placed within Titanosauria. Most other 'middle' Cretaceous East Asian sauropods are probably non-titanosaurian somphospondylans, but at least Xianshanosaurus appears to belong to the titanosaur radiation. Our analyses also recover the Early Cretaceous European sauropod Normanniasaurus genceyi as a 'derived' titanosaur, clustering with Gondwanan taxa. These results provide further support for a widespread diversification of titanosaurs by at least the Early Cretaceous.

Taxonomic affinities of the putative titanosaurs from the Late Jurassic Tendaguru Formation of Tanzania: Phylogenetic and biogeographic implications for eusauropod dinosaur evolution

Article

Jan 2019

The Late Jurassic Tendaguru Formation of Tanzania, southeastern Africa, records a rich sauropod fauna, including the diplodocoids Dicraeosaurus and Tornieria, and the brachiosaurid titanosauriform Giraffatitan. However, the taxonomic affinities of other sympatric sauropod taxa are poorly understood. Here, we critically reassess and redescribe these problematic taxa, and present the largest phylogenetic analysis for sauropods (117 taxa scored for 542 characters) to explore their placement in Eusauropoda. Janenschia robusta has played a prominent role in discussions of titanosaur origins, with various authors referring at least some remains to Titanosauria, a clade otherwise known only from the Cretaceous. Redescription of the holotype of Janenschia, and all referable remains, supports its validity and placement as a nonneosauropod eusauropod. It forms a clade with Haestasaurus from the earliest Cretaceous of the UK, and the Middle/Late Jurassic Chinese sauropod Bellusaurus. Phylogenetic analysis and CT scans of the internal pneumatic tissue structure of Australodocus bohetii tentatively support a non-titanosaurian somphospondylan identification, making it the only known pre-Cretaceous representative of that clade. New information on the internal pneumatic tissue structure of the dorsal vertebrae of the enigmatic Tendaguria tanzaniensis, coupled with a full redescription, results in its novel placement as a turiasaur. Tendaguria is the sister taxon of Moabosaurus, from the Early Cretaceous of North America, and is the first turiasaur recognized from Gondwana. A previously referred caudal sequence cannot be assigned to Janenschia and displays several features that indicate a close relationship with Middle–Late Jurassic East Asian mamenchisaurids. It can be diagnosed by six autapomorphies, so we erect the new taxon Wamweracaudia keranjei gen. et sp. nov. The presence of a mamenchisaurid in the Late Jurassic of southern Gondwana indicates an earlier and more widespread diversification of this clade than previously realized, prior to the geographic isolation of East Asia. Our revised phylogenetic dataset sheds light on the evolutionary history of Eusauropoda, including supporting a basal diplodocoid placement for Haplocanthosaurus, and elucidating the interrelationships of rebbachisaurids. The Tendaguru Formation shares representatives of nearly all sauropod lineages with Middle Jurassic–earliest Cretaceous global faunas, but displays a greater range of diversity than any of those faunas considered individually. Biogeographic analysis indicates that the Tendaguru sauropod fauna was assembled as a result of three main phenomena during the late Early and/or Middle Jurassic: (1) invasions from Euramerica (brachiosaurids, turiasaurs); (2) endemism in west Gondwana (dicraeosaurids, diplodocids); and (3) regional extinctions that restricted the ranges of once widespread groups (mamenchisaurids, the Janenschia lineage). Multiple dispersals across the Central Gondwanan Desert are required to explain the distributions of Jurassic sauropods, suggesting that this geographic feature was at most a filter barrier that became easier to cross during the late Middle Jurassic.

Xenoposeidon is the earliest known rebbachisaurid sauropod dinosaur

Article

Full-text available

Jul 2018

Michael P Taylor

Xenoposeidon proneneukos is a sauropod dinosaur from the Early Cretaceous Hastings Group of England. It is represented by a single partial dorsal vertebra, NHMUK PV R2095, which consists of the centrum and the base of a tall neural arch. Despite its fragmentary nature, it is recognisably distinct from all other sauropods, and is here diagnosed with five unique characters. One character previously considered unique is here recognised as shared with the rebbachisaurid diplodocoid Rebbachisaurus garasbae from the mid-Cretaceous of Morocco: an ‘M’-shaped arrangement of laminae on the lateral face of the neural arch. Following the more completely preserved R. garasbae , these laminae are now interpreted as ACPL and lateral CPRL, which intersect anteriorly; and PCDL and CPOL, which intersect posteriorly. Similar arrangements are also seen in some other rebbachisaurid specimens (though not all, possibly due to serial variation), but never in non-rebbachisaurid sauropods. Xenoposeidon is therefore referred to Rebbachisauridae. Due to its inferred elevated parapophysis, the holotype vertebra is considered a mid-posterior dorsal despite its elongate centrum. Since Xenoposeidon is from the Berriasian–Valanginian (earliest Cretaceous) Ashdown Formation of the Wealden Supergroup of southern England, it is the earliest known rebbachisaurid by some 10 million years. Electronic 3D models were invaluable in determining Xenoposeidon ’s true affinities: descriptions of complex bones such as sauropod vertebrae should always provide them where possible.

Reassessment of the Early Cretaceous Sauropod Astrodon johnsoni Leidy 1865 (Titanosauriformes)

Chapter

Full-text available

Jan 2005

Sauropod material from the Arundel Formation (Aptian-Albian boundary) of Maryland has been variously referred to Astrodon johnsoni Leidy 1865 or to Pleurocoelus nanus Marsh 1888. Most of the specimens are juvenile as demonstrated by the small size of the bones, the lack of neurocentra 1 fusion, absence of an olecranon, and underdevelopment of muscle scars. Contrary to some recent statements, the Arundel sauropod is diagnostic. Only a single sauropod taxon is present in the Arundel Formation, to which the name Astrodon johnsoni must be used under the Principle of the First Reviser of the International Code of Zoological Nomenclature .

The global sauropod fossil record

Article

Full-text available

Jan 1995

Species determination in sauropod dinosaurs with tentative suggestions for their classification

Chapter

Nov 1990

John S. McIntosh

In recent years dinosaurs have captured the attention of the public at an unprecedented scale. At the heart of this resurgence in popular interest is an increased level of research activity, much of which is innovative in the field of palaeontology. For instance, whereas earlier palaeontological studies emphasized basic morphologic description and taxonomic classification, modern studies attempt to examine the role and nature of dinosaurs as living animals. More than ever before, we understand how these extinct species functioned, behaved, interacted with each other and the environment, and evolved. Nevertheless, these studies rely on certain basic building blocks of knowledge, including facts about dinosaur anatomy and taxonomic relationships. One of the purposes of this volume is to unravel some of the problems surrounding dinosaur systematics and to increase our understanding of dinosaurs as a biological species. Dinosaur Systematics presents a current overview of dinosaur systematics using various examples to explore what is a species in a dinosaur, what separates genders in dinosaurs, what morphological changes occur with maturation of a species, and what morphological variations occur within a species.

Titanosaurs and the origin of "wide-gauge" trackways: A biomechanical and systematic perspective on sauropod locomotion

Article

Jan 1999

Two major ichnotypes of sauropod trackways have been described: "narrow-gauge," in which both manus and pes prints approach or intersect the trackway midline, and "wide-gauge," in which these prints are well apart from the midline. This gauge disparity could be the result of differences in behavior, body size, or morphology between the respective trackmakers. However, the biomechanics of locomotion in large terrestrial vertebrates suggest that sauropods were probably restricted in locomotor behavior, and the lack of systematic size differences between footprint gauges argues against body-size-related influences. We argue that skeletal morphology is responsible for gauge differences and integrate data from locomotor biomechanics and systematics with the track record to predict the hindlimb morphology of wide-gauge trackmakers. Broader foot stances in large, graviportal animals entail predictable mechanical consequences and hindlimb modifications. These could include outwardly angled femora, offset knee condyles, and a more eccentric femoral midshaft cross-section. A survey of sauropod hindlimb morphology reveals that these features are synapomorphies of titanosaurs, suggesting that they were the makers of wide-gauge trackways. The temporal and geographic distribution of titanosaurs is consistent with this hypothesis because wide-gauge trackways predominate during the Cretaceous and are found worldwide. Additional appendicular synapomorphies of titanosaurs are interpreted in light of identifying these animals as wide-gauge trackmakers. We suggest that titanosaurs may have used a bipedal stance more frequently than did other sauropods. These correlations between ichnology, biomechanics, and systematics imply that titanosaurs were unique among sauropods in having a more varied repertoire of locomotor habits.

Cretaceous: Sea levels peak as the North Atlantic opens

Article