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A new pterodactyloid pterosaur from the Wessex Formation
(Lower Cretaceous) of the Isle of Wight, England
Lorna Steel
a
, David M. Martill
b,
*, David M. Unwin
c
, John D. Winch
d
a
Dinosaur Isle Museum, Culver Parade, Sandown, Isle of Wight PO36 8QA, UK
b
School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth PO1 3QL, UK
c
Institut fu
¨r Pala
¨ontologie, Museum fu
¨r Naturkunde, Zentralinstitute der Humboldt-Universita
¨t zu Berlin,
Invalidenstraße 43, D-10115 Berlin, Germany
d
Rowena, St. John’s Road, Wroxall, Isle of Wight, UK
Received 14 July 2004; accepted in revised form 23 March 2005
Abstract
A new pterosaur specimen comprising a partial skull and associated postcranial elements from the Lower Cretaceous Wessex
Formation of Yaverland, Isle of Wight, southern England, is assigned to a new genus and species of ornithocheirid pterosaur,
Caulkicephalus trimicrodon gen. et sp. nov., based on several unique features including a heterodont dentition in which the fifth, sixth
and seventh teeth are reduced in size compared with those at positions 1e4 and 8e9; the presence of a frontoparietal crest and
maxillopremaxillary crest that do not unite over the antorbital fenestra or cranium; a palatal ridge that extends no further forward
than the eighth to ninth tooth pairs. The new taxon is the second species of pterosaur from the Wealden Group of the Wessex Basin.
Ó2005 Elsevier Ltd. All rights reserved.
Keywords: Reptilia; Pterosauria; Caulkicephalus; Early Cretaceous; Wealden Group; England
1. Introduction
Pterosaurs are rare in the Wealden Group of the UK
with only three described species currently considered
valid: Coloborhynchus clavirostris Owen, 1874 and
?Lonchodectes sagittirostris (Owen, 1874) from the
Hastings Sand Formation of Hastings, Sussex and
Istiodactylus latidens (Seeley, 1901) from the Vectis
Formation of the Isle of Wight (Unwin et al., 2000;
Howse et al., 2001; Unwin, 2001). Other named taxa
[‘‘O. clifti’’ (Mantell, 1844) and ‘‘O. curtus’’ (Owen,
1870) from the Wealden of Sussex and ‘‘Ornithocheirus
nobilis’’ (Owen, 1870) from the Wealden of the Isle of
Wight] are considered nomina dubia, because they are
based on non-diagnostic features (Howse et al., 2001).
Only the distinctive Istiodactylus latidens is known from
the Isle of Wight Wealden Group, and the two speci-
mens that can definitely be assigned to this taxon
(CAMMZ T707, BMNH R3877) both appear to have
come from the lagoonal sediments of the Vectis
Formation (Hooley, 1913; Howse et al., 2001).
Fragmentary, often indeterminate remains of pter-
osaurs, some possibly referable to the Ornithocheiridae,
have previously been reported from the Wessex Forma-
tion (Martill et al., 1996). These include a partial
postcranial skeleton (MIWG 5579) from the Wealden
Group, an isolated ornithocheirid tooth (MIWG 5318)
from the Vectis Formation of Barnes High, Isle
of Wight, a similar tooth from the Wessex Formation
of Yaverland (MIWG 2756), and the proximal part of
a left humerus in the collections of the Natural History
* Corresponding author.
E-mail addresses: lorna.steel@pterosaur.net (L. Steel), david.mar-
till@port.ac.uk (D.M. Martill).
0195-6671/$ - see front matter Ó2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.cretres.2005.03.005
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Cretaceous Research -- (2005) 1e13
Museum, London (BMNH R558), that was only
tentatively referred to Ornithocheirus by Lydekker
(1888). A considerable amount of well-preserved and
potentially diagnosable material has also been reported
from several private collections on the island (Green,
1995).
The new material described here represents the first
specifically identifiable pterosaur to have been discov-
ered in the Wessex Formation. It comprises parts of
a skull and possibly associated postcranial remains that
were discovered on the foreshore near Yaverland,
Sandown, Isle of Wight, throughout 2002 (some
material was obtained as early as 1995 by one of us:
JDW) by several independent collectors on a number of
separate occasions. Most of the material was found
loose on the beach, but one wing element, a quadrate
and an indeterminate long bone were found in situ.
Several bones in private collections, including one
element figured by Green (1995, p. 23, specimen number
0037JW), that come from the same locality may also
belong to this individual (JDW, pers. obs.). The material
described here is housed in the Dinosaur Isle Museum at
Sandown, Isle of Wight, under accession numbers
IWCMS 2002.189.1e4, 2002.233, 2002.234, 2002.236,
and 2003.2e4.
Abbreviations for institutions referred to in the text.
BMNH, the Natural History Museum, London;
CAMMZ, Cambridge University Museum of Zoology;
MIWG and IWCMS, Isle of Wight County Museum
Service at Dinosaur Isle, Sandown, Isle of Wight.
2. Locality and stratigraphy
The new specimen was found on foreshore exposures
of the Wessex Formation that are revealed from time to
time at Yaverland on the north-east end of Sandown
Bay, Isle of Wight (National Grid reference SZ 614852;
Fig. 1). This locality is one of two coastal areas on the
island where the Wessex Formation is exposed in cliffs
and wave-cut platforms (Fig. 1A). Active erosion results
in continuous new exposures, but landslips, especially
during the winter months, can make visits dangerous
while mudslides and beach sands can obscure outcrops.
At the time of writing, much of the wave cut platform at
Yaverland was covered by sand.
The section exposed at Yaverland comprises the upper
part of the Wessex Formation and the overlying Vectis
Formation of the Wealden Group, with younger beds,
representing a marine transgression, exposed to the
north-east of the bay (Fig. 2). Here the Wessex Formation
is of Barremian (Early Cretaceous) age, and comprises
a series of variegated mudstones with intermittent fluvial
sandstones, silty clays and occasionally plant debris beds.
The sequence represents a meander-belt floodplain
system with pond and ephemeral lake deposits (White,
1921; Stewart, 1981; Radley, 1994; Wright et al., 2000).
The plant debris beds are known for their abundant and
often extremely well preserved macro- and micro-
vertebrate remains, including dinosaurs, crocodilians,
turtles, amphibians, mammals and fishes (Martill and
Naish, 2001). The new pterosaur was obtained from one
of the plant debris beds (Bed 33 of Radley, 1994).
Typically, the plant debris beds are patchily cemented by
nodular siderite, contain abundant intraclasts and a high
percentage of plant remains ranging from leaf fragments
to logs several metres in length. Both lignite and fusain
occur. Pyrite, siderite, calcite and barite are common
diagenetic minerals but, unfortunately, the pyrite is
unstable and prone to decay in damp conditions. The
plant debris beds are believed to be the result of
intrabasinal flood events that transported plant debris
and carcasses, depositing them on the floodplains (Martill
N
Isle of Wight
Wealden Group outcrop A
B
Fig. 1. Locality map showing the Cretaceous fossil vertebrate locality
of Yaverland, Isle of Wight. In A, the shading represents outcrops of
the Wealden Group. In B, the Yaverland Member (new name) is
indicated as a black line in the cliffs and foreshore. The X marks the
new pterosaur site.
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and Naish, 2001). Many of the skeletons are disrupted,
possibly as a result of scavenging (Martill, 2001).
3. Preservation
The bones of the present specimen are black and well
preserved although there is a small amount of compac-
tion damage in places. A small area of compacta is
missing from the surface of the rostrum tip. Some parts
of the bones are coated with a thin layer of iron pyrite,
but most void space is filled with cemented mudstone
(Figs. 3e5). A small amount of grey mudstone with
abundant black plant debris has been left on one of the
bones to confirm the provenance of the specimen. The
surface of one bone is pitted, possibly as a result of
pyrite growth, although bioerosion may be responsible.
Fig. 2. Schematic stratigraphic section for the Wessex and Vectis formations at Yaverland, near Sandown, Isle of Wight, locating the horizon of
Caulkicephalus trimicrodon gen. et sp. nov. with an asterisk; simplified from Radley (1994).
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Some of the damaged surfaces are a consequence of
recent marine erosion.
Several of the skull fragments fit together and clearly
come from a single individual. It is assumed that the
remaining skull fragments, including a braincase found
in very close proximity to the holotype, and various
portions of postcranial skeleton obtained from the same
locality, all belong to the same individual. Although
there is no direct fit to confirm this, this proposal is
supported by several lines of evidence: the bones all
came from the same site; there is no duplication of
bones; they exhibit the same style of preservation; they
are completely consistent in size; and there is no
indication of the presence of more than one taxon.
4. Systematic palaeontology
Pterosauria Kaup, 1834
Pterodactyloidea Plieninger, 1901
Ornithocheiridae Seeley, 1870
Genus Caulkicephalus gen. nov.
Fig. 3. Rostrum of Caulkicephalus trimicrodon gen. et sp. nov., IWCMS 2002.189.1, 2. A, dorsal view. B, right lateral view. C, ventral view; D,
anterior view. Scale bar represents 10 mm.
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Derivation of name. Caulk; from Caulkhead, the
informal name for natives of the Isle of Wight: workers
from the Isle of Wight previously worked as caulkers in
the Solent dockyards; and cephalus, Greek, head.
Diagnosis. As for type and only known species (see
autapomorphies listed for type species below).
Caulkicephalus trimicrodon gen. et sp. nov.
Figs. 3e6
Derivation of specific name. A combination of tri,
three; micro, tiny and don, tooth, referring to the small
dental alveoli at tooth positions 5e7.
Fig. 4. Braincase of IWCMS 2002.189.3 and quadrate referred to Caulkicephalus trimicrodon gen. et sp. nov. Braincase in A, dorsal view, B, left
lateral view, C, posterior view, D, ventral view. E, left quadrate, (IWCMS 2003.2). Scale bar represents 10 mm.
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Holotype. IWCMS 2002.189.1, 2, 4, three contiguous
elements that form the anterior portion of the rostrum
(Fig. 3AeD).
Type locality and horizon. North-east Sandown Bay,
Yaverland, Isle of Wight (Fig. 1); upper part of Wessex
Formation, Lower Cretaceous (Barremian) (Fig. 2).
Referred material. Incomplete braincase bearing the
base of a sagittal crest (IWCMS 2002.189.3; Fig. 4Ae
D); left quadrate (IWCMS 2003.2; Fig. 4E); a fragment
of a possible jugal (IWCMS 2003.4); proximal part of
the left wing-phalanx 1 (ICWMS 2002.237; Fig. 5A);
four contiguous fragments of the shaft of a wing-
phalanx 1 (IWCMS 2002.234.1e4; Fig. 5C); distal part
Fig. 5. Other elements referred to Caulkicephalus trimicrodon gen. et sp. nov. A, proximal part of the left wing-phalanx 1, ICWMS 2002.237. B, distal
part of probable wing-phalanx 2, IWCMS 2002.233. C, four contiguous fragments of the shaft of wing-phalanx 1, IWCMS 2002.234.1e4. D, an
element possibly from the hind limb, IWCMS 2003.3. E, cross section of phalange showing cortical bone and spongiosa. Scale bars represent 10 mm:
left scale bar for A, B, D, E; right scale bar for C.
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of wing-phalanx ?2 (IWCMS 2002.233; Fig. 5B); frag-
ment of shaft of wing-phalanx ?4 (IWCMS 2002.236)
and an element possibly from the hind limb (IWCMS
2003.3; Fig. 5D).
Diagnosis. Ornithocheirid pterosaur in which
the maxillopremaxillary suture descends slightly posteri-
orly; the fifth to seventh pair of dental alveoli are
significantly smaller than pairs 1e4and8e10, and the
palatal ridge extends no further anteriorly than dental
alveoli 8 and 9. Uniquely for the Ornithocheiridae this taxon
possesses both frontoparietal and maxillopremaxillary
crests and these do not merge over the nasoantorbital
fenestra or cranium.
5. Description
The holotype consists of three contiguous fragments
of the rostrum (Fig. 3, Table 1). These three pieces fit
together to form the anterior part of the rostrum and
include parts of the premaxillae and maxillae extending
posteriorly to a position that terminates just prior to the
anterior margin of the nasoantorbital fenestra. The
margin of the nasoantorbital fenestra is not preserved,
but an arc of crushed bone suggests that the margin of
this fenestra may have been close to the edge of the
preserved section. A fourth bone fragment, an in-
complete braincase, is presumed to belong to the same
individual as the rostral material (see ‘‘Preservation’’
above).
5.1. Rostrum
The preserved part of the rostrum is 290 mm in length
and is laterally compressed for most of its length,
though some of this may in part be exaggerated by slight
compaction, as indicated by numerous small cracks. It
is 30 mm wide at the second tooth pair, narrowing to
20 mm in width between tooth pairs 9e10. It then
expands in width posteriorly until it reaches a breadth of
42 mm at tooth pair 14. The dorsal margin of the
Fig. 6. Drawings of the holotype rostrum of Caulkicephalus trimicrodon gen. et sp. nov., IWCMS 2002.189.1, 2, 4 in right lateral view (A, C) and
palatal view (B, D).
Table 1
Selected measurements of Caulkicephalus trimicrodon gen. et sp. nov.
from the Wessex Formation (Lower Cretaceous, Barremian) of the Isle
of Wight
Skull elements
Rostrum (three pieces combined)
Width of palate at third tooth pair 30 mm
Width of palate at ninth tooth pair 24 mm
Width of palate at fourteenth tooth pair 38 mm
Estimated length of rostrum from anteriortiptomarginofnasoantorbital
fenestra 300 mm
Height of rostrum at lowest point between maxillo/premaxillary crest
and cranium 36 mm
Postcranial elements
Posterior segment of proximal end of first phalanx of left wing IWCMS
2002.237 (as preserved)
Length of fragment 44 mm
Width 30 mm
Depth 19 mm
Compacta thickness 0.2e0.8 mm
Portion of wing-phalanx 1 IWCMS 2002.234.1e4 (as preserved)
Length 245 mm
Width 29 mm
Depth 14 mm
Compacta thickness 0.5e2.5 mm
Distal portion of wing-phalanx ?2 IWCMS 2002.233 (as preserved)
Length 64 mm
Width proximally 30 mm
Width distally 30 mm
Depth 15 mm
Compacta thickness 0.1e0.2 mm
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rostrum descends towards the anterior tip of the jaw
and, as is in other ornithocheirids, the section anterior to
the fifth pair of dental alveoli is transversely expanded to
accommodate the first four pairs of large fang-like teeth
(Unwin, 2001).
A premaxillary crest is present, but it is damaged and
much of its dorsal margin is missing. The crest does not
extend to the anterior tip of the snout, but commences
a short distance posterior to it, level with the third
alveolar pair. Several small nutritive foramina are visible
on both lateral margins of the rostrum. They are evenly
distributed; otherwise the surface of the bone is smooth.
The posterior most fragment of the rostrum (IWCMS
2002.189.4) measures 126 mm in length and is tapered,
widening from 23 mm anteriorly to 38 mm posteriorly.
Ventrally, it comprises the palate and dental borders,
and bears a medial palatal ridge along its entire length.
The dorsal surface is arcuate as it rises both anteriorly
towards the maxillopremaxillary crest and posteriorly
towards the cranium. The maxillopremaxillary suture is
well defined on the left side. It is straight and extends
ventroposteriorly.
The anterior tip of the palate begins to curve upwards
from a point just behind the second alveolus, at an angle
that gradually increases to about 80 from the
horizontal. The dorsal margin of the rostrum arcs
ventrally to meet the ventral margin forming a rounded
anterior tip. The posterior part of the palate is encrusted
with a thin coating of pyrite approximately 0.25e0.5 mm
thick, but the median palatal ridge is clearly seen despite
the pyrite coating. This ridge is not very pronounced and
is not visible in lateral view. It is present on the posterior
portion of the palatal surface, but becomes less pro-
nounced anteriorly and disappears completely between
the eighth and ninth alveoli.
The gradual upturn of the palate towards the tip of
the rostrum means that the first two pairs of tooth
sockets point anteroventrally, while the remaining
alveoli are orientated ventrolaterally in the alveolar
margin and the posterior most alveoli point ventrally.
The interalveolar areas are gently concave while the
rims of the alveoli project beyond the palatal surface.
The palatal surface bears several paired nutritive
foramina between the first four pairs of alveoli. The
two foramina in each pair are linked by a groove that is
5e6 mm long. There is a small pit just posterior to the
first alveolus on the right side. Whether this is
a pathological feature, a nutritive foramen, or recent
damage is uncertain, but a similar, though medially
located pit, is seen in the ornithocheirid Coloborhynchus
wadleighi (Lee, 1994).
The dental alveoli vary greatly in size, but are all
approximately oval, with the longest diameter orientated
anteroposteriorly. The first pair are of slightly different
sizes (Table 2), the left being only slightly larger than the
right. The second pair is substantially larger than the first
pair, while the third pair, only preserved on the right side,
is the largest in the entire dental series. The fourth pair,
again only preserved on the right side, is substantially
smaller than the third and similar in size to the first pair.
There is very little space between consecutive alveoli in
this part of the rostrum: the interalveolar area is 4 mm
between alveoli 2 and 3, but less than half this distance
between alveoli 1 and 2 and between alveoli 3 and 4.
The first four pairs of dental alveoli are followed by
three smaller alveoli that, again, are only preserved on
the right side of the rostrum. The fifth pair of alveoli are
less than half the anteroposterior width of the third,
while the sixth and seventh are of almost the same size
and slightly smaller than the fifth (Table 2). The space
between consecutive alveoli in this group is almost
equivalent to the length of individual alveoli. Posterior
to the seventh pair of alveoli there is a marked increase
in size with the eighth to tenth pairs of similar
dimensions and almost reaching the size of the first pair
of alveoli. These alveoli are also widely spaced; on
the right side alveoli 8 and 9 are separated by a gap
equivalent to one and one-half alveoli while the gap
between alveoli 9 and 10 on the right side is equivalent
to two alveoli, that on the left slightly less. Toward the
anterior end of the rostrum the left and right alveoli of
each pair are approximately parallel to one another, but
in the region of the ninth and tenth alveoli they become
increasingly staggered, those on the left side lying
slightly anterior to those on the right side.
The tips of replacement teeth are visible in the first
and ninth alveoli on the right side. They are oval in cross
section and pointed. Immediately posterior to the tenth
alveolus the specimen is broken. The third part of the
rostrum bears four alveoli on the left side and four on
the right side (alveoli 11e14) but they are not arranged
in pairs. These alveoli are elongate, the best preserved
measuring 7 !4mm (Figs. 3, 6), and with a long axis
sub-parallel to the dental border.
5.2. Referred braincase
The braincase (IWCMS 2002.189.3) consists of the
frontals, parietals, the supraoccipital and possibly dorsal
Table 2
Maximum diameters of the first ten pairs of dental alveoli (in mm)
Tooth pair Left Right
11110
21414
3e15
4e11
5e6
6e5.5
7e5.5
8e9e10
9e9e10
10 e9e10
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portions of the prootics, opisthotics and exoccipitals, all
fused into a solid, largely uncrushed and undistorted
box-like structure, in which all former bone contacts and
sutures appear to be obliterated (Figs. 4AeD, 8).
The ventral part of the braincase, composed of the
basioccipital and parts of the prootics and opisthotics, is
broken away and this fracture extends anteriorly
through the upper part of the orbits. The outer margins
of the braincase are eroded and the cranial crest is
broken off at its base (see below).
In dorsal view the braincase is seen to expand
laterally over the orbits, but then is strongly constricted
posterior to this region before expanding again to form
the occipital plate. The upper part of the inner wall of
the orbits appears to have been ossified (possibly by the
laterosphenoid).
The braincase bears evidence of a frontoparietal
crest. The base of the crest begins anteriorly at a point
between the orbits, and extends backwards along the
midline, but is separated from the occipital plate by
a small notch. The base of the crest seems to have been
widest just behind the orbits and its orientation suggests
that originally it extended posterodorsally. The left and
right sides of the base of the crest are approximately
parallel to each other, with some posterodorsally
directed divergence, and the crest is 7 mm thick at its
point of fracture. A little more posteroventrally the crest
is only 2 mm thick. Thus it seems likely that the crest
was relatively tall, narrow and posterodorsally directed,
as in Pteranodon and Ludodactylus (Frey et al., 2003).
The occipital plate has thin margins and now has
a relatively tall, narrow, pentangular outline, but may
have been much broader when complete. The plate is
slightly dished, concave both transversely and vertically
and has a low, vertically orientated median ridge.
Ventrally the plate is broken away along the dorsal
margin of the foramen magnum.
5.3. Quadrate
The left quadrate (IWCMS 2003.2) has a slightly
crushed dorsal region, but is well preserved ventrally.
The articulatory surface is 18 mm wide (Fig. 4E).
5.4. Postcranial skeleton
An incomplete wing phalanx 1 consists of four
contiguous pieces (IWCMS 2002.234.1e4; Fig. 5C,
Table 1). The bone is slightly dorsoventrally crushed,
but its original cross section was clearly an elongate
oval. Pyrite and mudstone completely fill the large
lumen of the bone and no trabeculae are visible on any
of the broken surfaces. The compacta is generally thin
(0.5 mm in places), but thickens to as much as 2.5 mm at
one end of the oval, which probably corresponds to the
anterior margin of the bone as observed in more
complete examples of ornithocheirids. The surface of
the bone is remarkably smooth, but bears two small
nutritive foramina that open on the better-preserved
(probably ventral) side of the phalanx.
A short section of a large bone (ICWMS 2002.237) is
identified as the posterior portion of the proximal end of
the left wing-phalanx 1 (Fig. 5A). Both ends and one
side are broken. The distal section reveals a loose
network of very fine trabeculae, none of which
completely crosses the lumen, just beneath the compac-
ta. The thickness of the compacta varies from approx-
imately 0.2e0.8 mm (Fig. 5E). The proximal region of
the bone exhibits a dense spongiosa typical of the
internal bone structure at an articulation. A small part
of the articular surface is still preserved and bears a deep
sulcus in which lie two pneumatic foramina. The
preserved dorsal surface is flat.
The distal part of another wing-phalanx (IWCMS
2002.233; Fig. 5B) is too narrow to represent wing-
phalanx 1, and probably represents part of a wing-
phalanx 2. The bone is slightly crushed and cannot be
assigned to a particular wing. Its surface is rather fibrous
and distally it has an unfinished appearance lacking the
compacta and exposing the bony trabeculae. This may
indicate that this particular part of the skeleton was still
growing, though in the braincase a lack of clearly visible
sutures suggests a nearly mature individual. It is difficult
to determine the thickness of the compacta at the
broken end, but it appears to be approximately 0.1e
0.2 mm thick.
A piece of wing-phalanx (IWCMS 2002.236), possi-
bly representing wing-phalanx 4, has a compacta
ranging from 0.2 to 0.5 mm in thickness. Again, the
thickest compacta are found in the vertices of the oval
cross section. A few tiny trabeculae are visible immedi-
ately beneath one area of the compacta, but they do not
span the entire width of the lumen. The smooth surface
of the bone is marked by clusters of shallow, irregular
pits ranging from 0.3 mm to approximately 2.0 mm in
diameter, while the majority are around 0.8 mm. They
may be a consequence of bioerosion or the diagenetic
ingrowth of pyrite aggregates.
Two small pieces of compacta with an underlying
trabecular mesh were also recovered. They are both
from the thickened margin of a long bone, but do not fit
with any other preserved parts of the skeleton. Their
value lies in that they show the three-dimensional
structure of trabeculae in pterosaur long bones. What
appears to be a network of bars when viewed in a two-
dimensional surface, such as a transverse break or a thin
section, is actually a system of closely opposed tubes
running parallel to the long axis of the bone. This
‘tubular’ system is located between the compacta and
the open lumen.
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6. Relationships to other pterosaurs
Assignment of Caulkicephalus to Ornithocheiridae is
supported by several synapomorphies including well-
established diagnostic features of the rostrum and
dentition (Bakhurina and Unwin, 1995; Unwin, 1995,
2001, 2002, 2003). As in other ornithocheirids, the
anterior end of the rostrum of Caulkicephalus is
transversely expanded, narrowest in the region of the
fifth tooth pair and widens again posteriorly. The size
distribution in the dentition shows a distinctive double
peak, with the largest teeth occurring at position three
and around position nine, and the smallest at position
five. Caulkicephalus also exhibits several characters that
appear to be restricted to ornithocheiroids (Istiodacty-
lus C(Ornithocheiridae CPteranodontia)). These in-
clude the presence of a low, bony sagittal crest with
a smooth dorsal margin on the rostrum and a narrow,
laterally compressed, posterodorsally directed, fronto-
parietal sagittal crest (though not certainly a synapo-
morphy of the Ornithocheiroidea; the crests of genera
included within Ornithocheiroidea differ structurally
from crests encountered in Azhdarchoidea) (NB:
Unwin, 2003 lists ‘‘tall, narrow frontal crest’’ as
a synapomorphy of Pteranodontia, though this feature
was reported by Frey et al., 2003 for the ornithocheirid
Ludodactylus. This feature may be synapomorphic for
the Euornithocheira but was secondarily lost in some
genera).
Caulkicephalus differs from Istiodactylus, the best
known Isle of Wight pterosaur (Howse et al., 2001),
which has a dorsoventrally compressed rostrum that
superficially resembles a duck’s beak and has labiolin-
gually compressed, triangular teeth (Hooley, 1913;
Howse et al., 2001). Istiodactylus is clearly distinct
from Caulkicephalus, as are the edentulous pterano-
dontians (Pteranodontidae CNyctosaurus) from the
Upper Cretaceous of North and South America
(Wellnhofer, 1991).
The ornithocheirid and ornithocheiroid characters
cited above also show that Caulkicephalus cannot be
assigned to any of the other three major pterodacty-
loid clades: Dsungaripteroidea (Germanodactylidae C
Dsungaripteridae), Azhdarchoidea (Tapejara C(Tu-
puxuara CAzhdarchidae)) and Ctenochasmatoidea
(Cycnorhamphus C(Pterodactylus CLonchodectidae C
Ctenochasmatidae). Dsungaripteroids have edentulous
jaw tips and short, squat teeth in swollen alveoli that are
largest toward the caudal end of the tooth row while
azhdarchoids are toothless. Generally, ctenochasmatoids
have relatively large numbers of teeth of sub-equal size
but, in one case, Cearadactylus, the dentition is similar to
that of ornithocheirids (Unwin, 2002). However, it is
unlikely that this taxon and Caulkicephalus share a close
relationship because Cearadactylus has a very distinctive
step in the ventral profile of the rostrum (Leonardi and
Borgomanero, 1985), and the rostrum has a low lateral
profile anteriorly, unlike that of Caulkicephalus, in which
the rostrum is as deep as it is wide. Cearadactylus also
lacks several key ornithocheiroid apomorphies, but
shares a number of characters in common with cteno-
chasmatoids (see Unwin, 2002, for full discussion).
6.1. Comparison with other ornithocheirids
Several taxa are currently included within the
Ornithocheiridae, though the validity of some remains
in doubt. Unwin (2001, 2003), in a systematic revision of
the Ornithocheiridae, included the genera Anhanguera,
Brasileodactylus,Coloborhynchus,Haopterus and Orni-
thocheirus.Frey et al. (2003) considered Anhanguera to
be a possible junior synonym of Coloborhynchus (see
also Unwin, 2001, 2002) and proposed a new genus,
Ludodactylus, to accommodate an ornithocheirid from
the Aptian Crato Formation of Brazil that lacks
a premaxillary crest, but possesses a pteranodontid-like
parietal crest. Frey and Martill (1994) also consider
Arthurdactylus from the Crato Formation (Lower
Cretaceous, Aptian) of Brazil to belong within the
Ornithocheiridae, an assignment tentatively supported
by Unwin (2003), but this taxon is known only from
postcranial remains. Here comparisons are made with
those taxa in which the skull, or at least the rostrum, is
preserved (Fig. 7).
Ornithocheirus, known from the Santana Formation
of Brazil (Wellnhofer, 1987; Fastnacht, 2001) and the
Cambridge Greensand of England (Unwin, 2001)is
distinguished from all other ornithocheirids by the
vertical orientation of even the anteriormost teeth, the
absence of any anterior upcurving of the palate and
the development of a large sagittal premaxillary crest,
with a flat anterior face, that is situated on the anterior
tip of the rostrum (Wellnhofer, 1987; Unwin, 2001). Not
one of these characters is present in the new pterosaur
material from Yaverland and it cannot be assigned to this
taxon. All other ornithocheirids in which the rostrum is
preserved, including Caulkicephalus, show some degree
of upcurving of the palate anteriorly, and an anteroven-
tral orientation of at least the first two pairs of teeth.
Haopterus, from the Yixian Formation of Liaoning
Province, China (Wang and Lu
¨, 2001), appears to be
distinct from Caulkicephalus because in the former tooth
pairs 5e7 show a marked increase in size (Wang and Lu
¨,
2001), whereas in the latter they are subequal in size. In
addition, the gaps between tooth positions are distinctly
greater in Haopterus, and this ornithocheirid also lacks
a sagittal rostral crest or frontoparietal crest (Wang and
Lu
¨, 2001), although this could be attributed to sexual
dimorphism (Bennett, 1992) or the relative immaturity
of the single known specimen of Haopterus gracilis
compared to the single known example of Caulkicepha-
lus trimicrodon.
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Ludodactylus, from the Crato Limestone Formation
of Brazil (Frey et al., 2003) and the Yaverland pterosaur
share one unique character in common when compared
with other ornithocheirids, namely the presence of
a narrow, posterodorsally directed frontoparietal crest,
though quite how tall it was in Caulkicephalus cannot be
established. This structure is absent in some ornitho-
cheiroids (Istiodactylus) or not known, but present in the
pteranodontians Pteranodon (Bennett, 2001) and Nyc-
tosaurus (Bennett, 2003). Currently, character state
optimisations do not support a single origin for this
character; thus it appears to have arisen independently
in Ornithocheiridae and Pteranodontia (Unwin, 2003),
but further exploration of relationships within Ornitho-
cheiroidea is needed to establish this more firmly.
Ludodactylus and Caulkicephalus also exhibit remark-
ably similar patterns of size distribution in the dentition,
but are distinguished by the presence, in Ludodactylus,
of a relatively large tooth pair at position seven, greater
spacing between tooth positions 1e7, a less abrupt and
more modest degree of upturn of the palate, the anterior
projection of the first three rather than just the first two
pairs of teeth, a maxillo/premaxillary suture that meets
the dorsal border of the nasoantorbital fenestra and the
absence of a sagittal crest on the rostrum (Frey et al.,
2003).
The Yaverland pterosaur exhibits numerous similar-
ities to the nexus of species currently assigned to
Coloborhynchus and Anhanguera. The degree of upturn
of the palate is identical to that seen in many of these
species, although an even greater degree of upturn is
seen in some species of Coloborhynchus (e.g. Owen,
1874; Lee, 1994; Fastnacht, 2001). Patterns of tooth size,
spacing and orientation (Kellner and Tomida, 2000;
Fastnacht, 2001) are also remarkably similar, although
only in Caulkicephalus is tooth pair 7 of similar size to
5 and 6. Caulkicephalus is also distinguished by the
discontinuation, anteriorly, of the median ridge on the
palate, in contrast to species of Coloborhynchus/Anhan-
guera where typically it extends forward to at least
the fourth tooth pair (Wellnhofer, 1987, 1991; Lee,
1994; Unwin, 2001). Unlike Caulkicephalus, where the
Fig. 7. Dental alveolar morphologies of pterosaurs. These diagrams are schematic and aim to show the distribution of large, medium-sized and small
teeth in each taxon. Horizontal lines indicate points of upward flexure of the palatal surface. Data taken mainly from Kellner and Tomida (2000);
Fastnacht (2001); Unwin (2001) and Wang and Lu
¨(2001).
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11L. Steel et al. / Cretaceous Research -- (2005) ---e---
maxillo/premaxillary suture trends toward the ventral
margin of the nasoantorbital fenestra, in Coloborhyn-
chus and Anhanguera this suture meets the dorsal border
of the fenestra (e.g., Kellner and Tomida, 2000).
6.2. Summary
The new Yaverland pterosaur is undoubtedly an
ornithocheirid, and similar to several species that belong
to this family. However, it lacks distinguishing features
of all genera currently included in this taxon and
represented by cranial material, but exhibits a number
of characters (maxillo/premaxillary suture descends
slightly posteriorly, fifth to seventh pair of dental alveoli
of similar size and significantly smaller than pairs one to
four; palatal ridge extends no further anteriorly than
dental alveoli 8 and 9; and presence of fronto/parietal
and maxillo/premaxillary crests that do not merge over
the nasoantorbital fenestra or cranium) that are not
found in any other ornithocheirid. Consequently, we
assign this taxon to a new genus and species of the
Ornithocheiridae.
In addition to their uncertain taxonomic status, several
taxa currently assigned to Ornithocheiridae, including
Caulkicephalus, are too poorly known for their interre-
lationships to be resolved with any certainty. Moreover,
few, if any, of the character states discussed above that
occur in more than one genus show clear cut patterns of
distribution or some degree of correlation. Clearly, more
complete specimens and much work will be needed to
disentangle the systematics of ornithocheirids.
7. Discussion
Previous findings (Martill et al., 1996) hinted at the
presence of ornithocheirids in the Wessex Formation
(Barremian), and this is now confirmed by the discovery
of C. trimicrodon. Ornithocheirids have already been
widely reported from the Lower Cretaceous of Western
Europe (Unwin et al., 2000, table 1; Unwin, 2001),
although not with any certainty from the Barremian.
This new record fills that gap and further encourages the
idea that ornithocheirids were present in Western
Europe throughout the Early Cretaceous.
An unusual feature of the material described here is its
discovery in a plant bed deposited within a fluvial
continental setting. Most ornithocheirids have been
recovered from marginal or fully marine sediments
(Unwin, 2001, table 1) and they are thought to have
had a life style broadly similar to that of some modern
ocean-going birds such as the Albatross and Frigate
Bird. This record of an ornithocheirid preserved in
a continental environment adds to other recent reports of
these pterosaurs from similar settings (Unwin et al.,
2000; Unwin, 2001), although it is still not clear if
these represent accidental occurrences or indications that
some ornithocheirids lived in terrestrial environments.
Only one other pterosaur, Istiodactylus latidens, has
so far been reported from the Isle of Wight and,
at present, is only certainly known from the Vectis
Formation (Martill and Naish, 2001). Recently, Mr.
S. Sweetman recovered a small, laterally compressed,
triangular tooth crown with thin enamel from a plant
debris bed within the Wessex Formation that may be
referable to Istiodactylus. If this preliminary identifica-
tion is verified it would suggest that species of
Caulkicephalus and Istiodactylus may have been sym-
patric, which is reasonable in that the dentition of these
taxa is markedly different and hints at quite distinct and
specialised life styles.
Acknowledgements
We especially thank Master Dan Davies and his
family, Gavin Leng, Tom Winch, Claire Winch, Martin
New and Martin Munt for finding the remains of the new
pterosaur. We are grateful to Mick Green, Steve Hutt,
Martin Munt, Michael Fastnacht, Natasha Bakhurina,
Darren Naish and Dino Frey for helpful comments. We
thank Mike Bishop and Martin Munt of Dinosaur Isle
(Isle of Wight Council) for allowing us to work on the
new material, and Steve Sweetman for access to un-
published data. We thank Mr. Keith Simmonds for his
excellent preparation of parts of the specimen. We also
thank Jenny Clack for allowing us to borrow a specimen
of Istiodactylus, and Sandra Chapman and Angela
Milner (Natural History Museum, London), David
Norman (Sedgwick Museum, Cambridge), Dino Frey
(Staatssammlung fu
¨r Naturkunde, Karlsruhe, Ger-
many), Peter Wellnhofer (Bayerische Staatssammlung
fu
¨r Pala
¨ontologie, Munich, Germany), Makoto Manabe
and Yuki Tomida (National Science Museum, Tokyo,
Japan), Y. Hasegawa and Y. Takakua (Gunma Museum
of Natural History, Gunma, Japan), S. Nabana (Iwaki
Fig. 8. Drawings of the braincase referred to Caulkicephalus, IWCMS
2002.189.3, in caudal view (A) and in right lateral view (B).
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12 L. Steel et al. / Cretaceous Research -- (2005) ---e---
Museum of Coal and Fossils, Iwaki, Japan), Y. Okazaki
(Kita Kyushu Museum of Natural History, Kita
Kyushu, Japan) and M. Norell (American Museum for
Natural History, New York, USA) for allowing us to
examine material in their care. Mr. Bob Loveridge is
thanked for help with photography. An anonymous
referee and Dr. Michael Fastnacht (Mainz) significantly
improved the manuscript. Thanks to Andrea Glazier,
Robin Toyne and the rest of the production crew of RDF
Media for their enthusiastic input. LS thanks the Isle of
Wight Council for supporting her work, DMM thanks
the University of Portsmouth.
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