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New Zealand Journal of Geology and Geophysics
ISSN: 0028-8306 (Print) 1175-8791 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzg20
A reappraisal of the Late Cretaceous Weddellian
plesiosaur genus Mauisaurus Hector, 1874
Norton Hiller, José P. O’Gorman, Rodrigo A. Otero & Al A. Mannering
To cite this article: Norton Hiller, José P. O’Gorman, Rodrigo A. Otero & Al A. Mannering (2017):
A reappraisal of the Late Cretaceous Weddellian plesiosaur genus Mauisaurus Hector, 1874, New
Zealand Journal of Geology and Geophysics, DOI: 10.1080/00288306.2017.1281317
To link to this article: http://dx.doi.org/10.1080/00288306.2017.1281317
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RESEARCH ARTICLE
A reappraisal of the Late Cretaceous Weddellian plesiosaur genus Mauisaurus
Hector, 1874
Norton Hiller
a
, José P. O’Gorman
b,c
, Rodrigo A. Otero
d
and Al A. Mannering
a
a
Canterbury Museum, Christchurch, New Zealand;
b
División Paleontología Vertebrados, Museo de La Plata, Universidad Nacional de La Plata,
Paseo del Bosque s/n., B1900FWA, La Plata, Argentina;
c
CONICET Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina;
d
Red
Paleontológica U-Chile, Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Universidad de Chile, Santiago, Chile
ABSTRACT
Research carried out on austral plesiosaurs from the Weddellian Biogeographic Province in the
decade since the last attempt to characterise the New Zealand elasmosaurid, Mauisaurus haasti
Hector, 1874 (On the Fossil Reptilia of New Zealand. Transactions and Proceedings of the New
Zealand Institute 6: 333–358), has prompted a reappraisal of this taxon and a new
consideration of its relationships. The hypodigms used in previous descriptions of the species
are shown to include specimens from a number of different taxa, and the defining
apomorphy of Mauisaurus, a hemispherical capitulum on the femur, has now been observed
in specimens known to belong to different clades. Mauisaurus is now regarded as
nomen dubium with possible affinities with the Subfamily Aristonectinae. A re-assessment of
the most complete specimen previously assigned to Mauisaurus suggests it is a typical long-
necked elasmosaurid closely comparable to Tuarangisaurus keyesi Wiffen and Moisley,
1986 (Late Cretaceous reptiles (Families Elasmosauridae and Pliosauridae) from the
Mangahouanga Stream, North Island, New Zealand. New Zealand Journal of Geology and
Geophysics 29: 205–252).
ARTICLE HISTORY
Received 25 July 2016
Accepted 7 January 2017
KEYWORDS
Plesiosauria; Elasmosauridae;
Mauisaurus;Tuarangisaurus;
Late Cretaceous; Weddellian
Province; New Zealand
Introduction
The genus Mauisaurus Hector, 1874 was established on
material from the Upper Cretaceous of New Zealand
and was one of the earliest plesiosaurian taxa to be
recorded from the Southern Hemisphere. Although
by today’s standards Hector’s(1874) diagnosis would
be regarded as woefully inadequate, from the time of
its erection, the genus has been accepted as valid and
numerous specimens from New Zealand and elsewhere
have been assigned to it. It has even penetrated the
awareness of the general public through postage
stamps and coins dedicated to it (Figure 1) and through
popular books on New Zealand fossils (e.g. Cox 1991;
Long 1998). Throughout its long history, the compo-
sition of the hypodigm on which it was based has
undergone a number of revisions (Welles 1962; Welles
& Gregg 1971; Hiller et al. 2005). Now, as a result of
discoveries made in South America and the Antarctic
Peninsula over the last decade and the research these
have supported (Otero et al. 2010,2012;O’Gorman
2013;O’Gorman et al. 2014a,2015; Otero et al. 2014,
2015a,2015b), we believe that this is an appropriate
time to re-examine Mauisaurus and all the specimens
that have been assigned to it. Here, we examine Hec-
tor’s original concept of the taxon and the material
on which it was based. We go on to look at how the
concept evolved as more material was discovered in
New Zealand and subsequently how more recent
discoveries made in other parts of the Weddellian Bio-
geographic Province (Figure 2; Zinsmeister 1979) have
impacted on the concept.
The following institutional abbreviations are used in
this article: AMNH, American Museum of Natural
History, New York, USA; BMNH, Natural History
Museum, London, UK; CM, Canterbury Museum,
Christchurch, New Zealand; DM, Museum of New
Zealand Te Papa Tongarewa, Wellington, New Zeal-
and; GNS CD, GNS Science, Lower Hutt, New Zealand;
KHM, Kaikoura Historical Museum, Kaikoura, New
Zealand; MLP, Museo de La Plata, Argentina; MML,
Museo Municipal de Lamarque, Río Negro, Argentina;
SDSM, South Dakota School of Mines and Technology,
Rapid City, South Dakota, USA; SGO.PV, Museo
Nacional de Historia Natural, Santiago, Chile; TTU
P, Museum of Texas Tech University, Lubbock,
Texas, USA; ZPAL, Institute of Paleobiology, Polish
Academy of Sciences, Warsaw, Poland.
Original concept of Mauisaurus
When Hector (1874) erected the genus Mauisaurus he
diagnosed it as ‘centrum of dorsal vertebrae equal in
length to the diameter, with smooth, concave sides,
and an inferior mesial ridge; articular facets circular,
flat, with a deep pit in the centre. Humerus with a
large tuberosity.’He assigned to it two species. The
© 2017 The Royal Society of New Zealand
CONTACT Norton Hiller nhiller@canterburymuseum.com Canterbury Museum, Rolleston Avenue, Christchurch 8013, New Zealand
NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS, 2017
http://dx.doi.org/10.1080/00288306.2017.1281317
first of these, Mauisaurus haasti, was based on eight
specimens (Table 1), Hector’s numbers 8a–h, compris-
ing vertebrae, paddle bones, several pelvic elements and
a few rib fragments, from three different localities
(Figure 3). Of these specimens, 8dand 8eare now miss-
ing and 8hturns out to be mosasaur teeth. Indeed, one
tooth was figured by Knight (1874) and identified as
mosasaur in the same volume in which Hector’s paper
appeared. The most significant of Hector’s specimens
is 8a, comprising fragmentary pubes, a partial ilium
and most of the right hind paddle (Figure 4). Hector
(1874) mistakenly identified the bones as coming from
the pectoral region of the skeleton rather than the pelvic.
The second species assigned by Hector (1874)to
Mauisaurus is M. brachiolatus, based on two speci-
mens; 9athe proximal end of a very large humerus
and 9ba left humerus plus radius and radiale. The
name of this species has been the source of some con-
fusion. In the description of the bones, latibrachialis
was the specific epithet applied (Hector 1874, p. 350)
but in the list of specimens it is given as brachiolatus
(Hector 1874, p. 336). Apparently, the former was a
mistake that was corrected by Hector in an erratum
slip. Hector gave no indication as to why he believed
the two species, haasti and brachiolatus, should be
placed in the same genus.
Welles (1962), in a review of Cretaceous plesiosaurs,
designated Hector’s specimen 8a as the lectotype of
M. haasti. He regarded the pubes as being long and
narrow and stated they could be pliosaurian
(sensu lato). This view was apparently reinforced by
the femur, which Welles (1962) described as being
very narrow distally and quite different from other ple-
siosaurs in having a hemispherical capitulum with a
large trochanter dipping steeply posteriorly and separ-
ated from the capitulum by a broad groove (Figure 4).
Additionally, Welles (1962) identified the very small
fibular facet as a very unusual feature.
It appears that Welles (1962) did not examine the
specimen itself but based his opinion on his interpret-
ation of the illustration provided by Hector (1874, pl.
29). It seems that he failed to appreciate that this
shows an oblique latero-ventral view of the femur,
even though Hector (1874, p. 363), in his explanation
of the plate, pointed out that the paddle had nearly
one-third greater width than shown.
Welles (1962) placed M. brachiolatus as nomen
vanum (nomen dubium in modern ICZN usage) as
the material on which it is based is indeterminate.
Later modifications of the concept
Welles and Gregg (1971), in their review of the Late
Cretaceous marine reptiles of New Zealand, produced
a revised diagnosis and the first detailed description
Figure 1. A, Commemorative coin and B, C, postage stamps
bearing an image of Mauisaurus.
Figure 2. The Weddellian Biogeographic Province in Late Cre-
taceous times, based on Zinsmeister (1979: figure 3). Black dots
indicate localities from which specimens mentioned in the text
were derived.
Table 1. Specimens used by Hector (1874) in the original description of Mauisaurus haasti.
Catalogue
number Material Locality; likely age Comment
8a (DM R1529) Fragmentary pubes, partial ilium, right femur; most
other paddle bones
Jed River, Cheviot; middle
Campanian
Specimen designated lectotype of the species
by Welles (1962)
8b (DM R829) Four vertebrae, ribs, humerus, paddle bones Haumuri Bluff; middle
Campanian
Rejected as non-diagnostic by Welles and Gregg
(1971)
8c (DM R1530) Very large dorsal vertebra Haumuri Bluff; middle
Campanian
Rejected as non-diagnostic by Welles and Gregg
(1971)
8d Paddle Haumuri Bluff; middle
Campanian
Specimen missing
8e Four vertebrae Haumuri Bluff; middle
Campanian
Specimen missing
8f (DM R1531) 13 posterior cervical vertebrae Haumuri Bluff; middle
Campanian
Rejected as non-diagnostic by Welles and Gregg
(1971)
8g (CM Zfr 92) Seven large posterior dorsal vertebrae Waipara River Retained as a paralectotype by Welles and
Gregg (1971)
8h Cast of jaw fragment with teeth (original lost at sea) Waipara River Identified as mosasaur
2N. HILLER ET AL.
of M. haasti based on the lectotype (DM R1529), one of
the paralectotypes (Hector’s specimen 8g comprising
seven posterior dorsal vertebrae; CM Zfr 92) and
nine newly referred specimens (Table 2). They rejected
from the hypodigm Hector’s specimens 8b,8cand 8f,
which they regarded as non-diagnostic, placing them
in the Elasmosauridae indet. (DM R1530 and
DM R1531) and Plesiosauria indet. (DM R829),
respectively. Specimens 8dand 8ehad already been
lost by this time.
The specimens referred to M. haasti by Welles and
Gregg (1971) include Hector’s specimen 9a M. bra-
chiolatus (DM R878), Hector’s specimen 9b M. bra-
chiolatus (CM Zfr 88–90), Hector’s specimen 1c
Plesiosaurus australis (trunk of a juvenile CM Zfr 103),
BM R830 a broken distal humerus and ulna,
CM Zfr 30 the left humerus of a juvenile, CM Zfr 95
an adult left femur, CM Zfr 102 anterior part of a
pair of large coracoids, CM Zfr 104 anterior part of
a right coracoid and associated vertebrae and paddle
bones, and CM Zfr 109 the right femur of a juvenile.
So, Welles and Gregg’s(1971) hypodigm included
juvenile as well as adult material from seven different
localities.
More recently, in the last attempt to understand
M. haasti, Hiller et al. (2005) revised the hypodigm
yet again. They rejected CM Zfr 92, DM R878,
BM R830, CM Zfr 30 and CM Zfr 109, regarding
each as non-diagnosable, but they added the new speci-
mens CM Zfr 115, comprising some skull bones, an
almost complete vertebral series and bones from all
four limbs (see below) and KHM N 99–1079, pelvic
bones and gastralia from a very large individual
(Table 3). Once more, juvenile as well as adult material
was included from seven localities. This new revision
gave the first clear idea about the affinities of Maui-
saurus, mostly based on CM Zfr 115, which, using cur-
rent concepts, is a long-necked (at least 65 cervical
vertebrae), non-aristonectine elasmosaurid (sensu
Otero et al. 2012).
Figure 4. A copy of Hector’s(1874) illustration showing the lectotype of Mauisaurus haasti.
Figure 3. Map showing the localities in New Zealand from which Mauisaurus has been recorded in the past.
NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS 3
Recent research and its implications
Plesiosaur specimens from outside New Zealand and
referred to Mauisaurus have been recorded from Ant-
arctica and South America. Fostowicz-Frelik and
Gaździcki (2001) tentatively referred to Mauisaurus
sp. a postcranial skeleton from middle-to-upper Maas-
trichtian beds of Seymour Island (Marambio Island),
Antarctica, based on the presence of the hemispherical
head of the femur. Later, Gasparini et al.(2003)
referred two specimens from upper Maastrichtian
beds of northern Argentinean Patagonia to cf. Maui-
saurus sp. based on the similarities with the humeri
referred by Welles and Gregg (1971)toMauisaurus;
Martin et al.(2007) also referred to Mauisaurus sp. a
juvenile specimen from Maastrichtian levels of Vega
Island, Antarctica, based on the presence of a rounded
end of the femur, a conical ventral process of the cor-
acoids, and fork-like gastralia. Subsequently, Otero
et al. (2010) referred to this genus two propodials
from upper Maastrictian beds of central Chile, based
on the presence of a distinctive large hemispherical
femoral head, which then was still regarded as an auta-
pomorphy of M. haasti, as pointed out previously
(Welles 1962; Welles & Gregg 1971). Otero et al.
(2010) avoided a specific determination due to differ-
ences in size between the studied specimens and the
lectotype of M. haasti.
In the latest revision of Patagonian and Antarctic
elasmosaurids, made during research for a PhD thesis,
one of the current authors (JPO’G) discussed whether
Mauisaurus was present among the records from
Argentinean Patagonia and the Antarctic Peninsula.
One of the main conclusions was that a hemispherical
femoral capitulum is present among members of the
Aristonectinae. However, New Zealand specimen
CM Zfr 115, placed in Mauisaurus by Hiller et al.
(2005), is a long-necked form with more than 60 cervi-
cal vertebrae and clearly not an aristonectine, thus rais-
ing the question about the validity of the concept of
Mauisaurus. This result, with additional information
from Kaiwhekea katiki Cruickshank & Fordyce, 2002
and Aristonectes quiriquinensis Otero et al. 2014, was
discussed in detail by Otero et al. (2015a) and it has
become clear that femora with strongly hemispherical
capitula are present in more than one aristonectine
and also in the non-aristonectine elasmosaurid
CM Zfr 115.
In recent publications, the current authors have
questioned the validity of the M. haasti hypodigm.
O’Gorman et al. (2014b) showed that CM Zfr 104
belongs to the clade Aristonectinae, whereas CM Zfr 115
is a typical long-necked elasmosaurid. Also, Otero et al.
(2015a) have shown that the presence of hemispherical
capitula on the femora, a character once believed to be
unique to Mauisaurus and thus its defining
Table 2. Specimens referred by Welles and Gregg (1971)toMauisaurus haasti.
DM R1529 Pelvis and paddle Jed River, Cheviot; middle
Campanian
Lectotype
CM Zfr 92 Seven posterior dorsal vertebrae Waipara River; early
Maastrichtian
Paralectotype; rejected as non-diagnostic by Hiller et al. (2005)
9a (DM R878) Proximal end of left humerus Haumuri Bluff; middle
Campanian
Originally a syntype of Hector’sM. brachiolatus; rejected as non-
diagnostic by Hiller et al. (2005)
9b (CM Zfr 88–
90)
Left humerus, radius and radiale Heathstock, upper Waipara The other syntypes of M. brachiolatus; rejected as non-diagnostic by
Hiller et al. (2005)
1c (CM Zfr 103) Body and tail of juvenile Bobys Stream, middle
Waipara; early
Maastrichtian
Originally placed in Plesiosaurus australis (Owen) by Hector (1874);
made holotype of Cimoliasaurus caudalis by Hutton (1894)
BM R830 Broken distal end of humerus
with ulna
Haumuri Bluff; middle
Campanian
Rejected as non-diagnostic by Hiller et al. (2005)
CM Zfr 30 Left humerus of a juvenile Waipara River; early
Maastrichtian
Rejected as non-diagnostic by Hiller et al. (2005)
CM Zfr 95 Left femur, tibia and fibula Birch Hollow, middle
Waipara; early
Maastrichtian
CM Zfr 102 Anterior parts of a pair of large
coracoids
Weka Creek; early
Maastrichtian
CM Zfr 104 Anterior of right coracoid,
vertebrae, rib fragments, limb
bones
Weka Creek; early
Maastrichtian
CM Zfr 109 Right femur of juvenile Probably Waipara River; early
Maastrichtian
Rejected as non-diagnostic by Hiller et al. (2005)
Table 3. Specimens included in Mauisaurus haasti by Hiller et al. (2005).
DM R1529 Pelvis and paddle Jed River, Cheviot; middle Campanian Lectotype
CM Zfr 88–90 Left humerus, radius and radiale Heathstock, Waipara River; early Maastrichtian
CM Zfr 95 Left femur, tibia and fibula Birch Hollow, middle Waipara; early Maastrichtian
CM Zfr 102 Anterior parts of a pair of large coracoids Weka Creek; early Maastrichtian
CM Zfr 103 body and tail of juvenile Bobys Stream, middle Waipara; early Maastrichtian
CM Zfr 104 Anterior of right coracoid, vertebrae, rib fragments, limb bones Weka Creek; early Maastrichtian
CM Zfr 115 substantially complete skeleton Ngaroma Station, Conway River; late Campanian
KHM N99–1079 Pubis, ilium and ischium of large individual Haumuri Bluff; middle Campanian
4N. HILLER ET AL.
apomorphy, is also seen in specimens that can be
referred to other taxa, particularly A. quiriquinensis
and K. katiki, both aristonectines. Also, the same
authors noted that the hemispherical articular head
can occur in both humeri and femora, as is the case
in A. quiriquinensis.
The presence of a conical ventral process on the ven-
tral side of the coracoids also appears to be present in
more than one lineage so cannot be used as a diagnostic
character of Mauisaurus as it was by Hiller et al. (2005).
Indeed, this feature is present in aristonectines (Otero
et al. 2012;O’Gorman et al. 2014a) and in non-aristo-
nectines (Welles 1952: figure 4a; Welles 1962: figure
5b). Therefore, it cannot be considered as a reliable
character for genus-level determinations.
Another piece of significant research in recent years
that can be brought to bear on our understanding of
the marine reptiles attributed to M. haasti is the devel-
opment of a refined biostratigraphy, based on dinofla-
gellate cysts, of the Upper Cretaceous deposits of New
Zealand (Roncaglia et al. 1999). This research showed
that the Conway Formation, the stratigraphic unit
from which many marine reptile remains were recov-
ered, is markedly diachronous, being older (middle–
late Campanian) at Haumuri Bluff in the north than
further south at Waipara River (late Campanian–
early Maastrichtian) (Figure 3). Extracting dinoflagel-
lates from matrix adhering to reptile bones allowed
Wilson et al. (2005) to determine fairly precise ages
for some individual marine reptile specimens. Such
stratigraphic control contrasts with the provenance of
most of the specimens from overseas that have been
referred to Mauisaurus.
The New Zealand specimens attributed to M. haasti
by Hector (1874) and those who followed him (Welles
& Gregg 1971; Wiffen & Moisley 1986; Hiller et al.
2005), and for which ages could be determined, are
spread over an age range extending from middle Cam-
panian to early Maastrichtian (Figure 5), a time span of
almost 10 million years (approximately 80–70 Ma).
When Argentinean, Chilean and Antarctic specimens
attributed to Mauisaurus are taken into account, the
age range for the genus could be extended to the late
Maastrichtian (see below). This seems an unusually
long stratigraphic range for a single species, apparently
without undergoing any evolution, given the plasticity
shown by plesiosaurs throughout their fossil record.
Other specimens assigned to Mauisaurus
New Zealand
In addition to the specimens mentioned above, Wiffen
and Moisley (1986) assigned a specimen (GNS CD 430)
comprising eight vertebrae, six dorsal and two sacral,
the head of a propodial, two isolated phalanges, and
Figure 5. Stratigraphic distribution of Mauisaurus specimens in New Zealand. See Table 3 and Figure 3 for locality details.
NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS 5
rib and ischia fragments to M. haasti. They regarded
this as the first specimen of Mauisaurus to have
been recorded from the North Island and identified
it based on the presence of a central swelling with a
medial pit on the articular faces of the vertebra.
They regarded this feature as a diagnostic character
of Mauisaurus. However, as pointed out by Hiller
et al. (2005, p. 599), this feature is known from elas-
mosaurid taxa other than Mauisaurus (e.g. CM Zfr 145,
a rather unusual specimen from New Zealand (Hiller
& Mannering 2005) and A. quiriquinensis, among
others) and, moreover, might depend on the ontogen-
etic stage of the individual. So Wiffen and Moisley’s
specimen must be regarded as an indeterminate elas-
mosaurid. The central perforation on the articular
facets likely represents the notochordal pit, and a pae-
domorphic condition could explain its presence in
adult individuals such that described by Wiffen and
Moisley (1986).
South America
Elasmosaurid material from upper Maastrichtian beds
of northern Patagonia was described by Gasparini et al.
(2003) and two specimens (MML‐PV3 and MML‐
PV4) were identified as cf. Mauisaurus sp. The
humerus of MML‐PV4 was likened to that of M. haasti,
in particular to CM Zfr 90. MML‐PV3 preserves the
proximal and distal ends of a femur, and although
the capitulum is convex it does not appear to be as
hemispherical as that of Mauisaurus. Also, the hemi-
spherical condition was, at that time, exclusively
regarded as diagnostic of the femur (but later verified
to occur also in the humerus). MML‐PV3 also includes
the intermedium of the hind limb, which Gasparini
et al. (2003) described as having a pentagonal shape
similar to that of M. haasti (Hector 1874, pl. 29, figure
a). Subsequently, Gasparini et al. (2007) re-assessed
this material and found that it was not identifiable to
generic level, although it could be placed in the
Elasmosauridae.
Otero et al. (2010) reported on two specimens, a
complete left femur (SGO.PV.135) and the proximal
portion of another putative left femur (SGO.PV.169),
from upper Maastrichtian beds of central Chile,
which they regarded as being identifiable as Maui-
saurus. A more recent re-assessment of this material
by Otero et al. (2015a) questioned this assignment
and concluded that the specimens are referable to
A. quiriquinensis. SGO.PV.169, previously considered
as a large ‘femur’was identified as the proximal part
of a left humerus of this species. An additional con-
clusion by Otero et al. (2015a) is that hemispherical
heads are indeed present both in femora and humeri,
and also, that such features depend on the ontogenetic
stages of the specimens.
Otero et al. (2015b) described several elasmosaurid
specimens from Maastrichtian beds in the Magallanes
Basin, southernmost Chile. Among them, a dwarf
adult postcranial skeleton, recovered from lower Maas-
trichtian beds and identified as an aristonectine, was
found to possess a hemispherical femoral capitulum.
Otero et al. (2015b) considered this specimen to be
related to specimens from Antarctica (ZPAL R.8 and
MLP 82-I-28-1) that at one time were regarded as clo-
sely related to Mauisaurus (see below).
Antarctica
In discussing the possible affinities of M. haasti, Hiller
et al. (2005) mentioned several specimens from the
upper Maastrichtian of the Antarctic Peninsula region
that they believed might possibly be related to that
species. An indeterminate elasmosaurid specimen,
TTU P 9221, was described by Chatterjee and Small
(1989) who observed central swellings with medial
pits on the articular faces of dorsal centra. They
noted that similar features were known in Mauisaurus
but did not assign their specimen to the genus. As men-
tioned above, these features are not diagnostic.
Specimen (MLP 82-I-28-1), a partial hind limb with
associated vertebral column, was described by Gaspar-
ini et al. (1984) from Seymour Island (Marambio
Island). This femur had a morphology, including a
hemispherical head, that Hiller et al. (2005) regarded
as being very close to Mauisaurus. Gasparini et al.
(1984) remarked that they had not seen anything
with a comparable morphology, an opinion reflecting
that of Welles (1962) when he nominated DM R1529
as the lectotype of M. haasti. The specimen was
reviewed by one of the present authors (JPO’G) during
research for a PhD thesis and placed as an indetermi-
nate elasmosaurid.
Fostowicz-Frelik and Gaździcki (2001) described a
subadult elasmosaurid (ZPAL R.8) from lower Maas-
trichtian beds (Klb2) of Seymour Island (Marambio
Island) stating that some features of the vertebral cen-
tra and the shapes of the tibia and proximal end of the
femur suggested that the bones belonged to Maui-
saurus or some closely related genus. However, they
concluded that the remains could not be identified.
Gasparini et al. (2003) referred to cf. Mauisaurus sp.
another specimen (TTU P 9217), originally described
by Chatterjee and Small (1989), on the grounds that
it was similar to one (MML‐PV4) they described
from Patagonia. As shown above, the Patagonian speci-
men is regarded as an indeterminate elasmosaurid, so
the Antarctic specimen must be similarly assigned.
Martin et al. (2007) described the articulated skel-
eton of a juvenile plesiosaurian (SDSM 78156) from
the Maastrichtian of Vega Island. Features of the
femora and coracoids, and the presence of forked gas-
tralia led them to identify the specimen as belonging in
6N. HILLER ET AL.
Mauisaurus but they were unable to provide a specific
assignment. They regarded the specimen as being very
similar to CM Zfr 103 from the Waipara River area of
New Zealand. We show below that Mauisaurus cannot
be adequately diagnosed so the Vega Island juvenile
must be placed as Elasmosauridae indet., as was indi-
cated by O’Gorman (2013). In addition, the specimen
(SDSM 78156) possesses anterior caudal centra with
octagonal articular facets (RA Otero, pers. obs. 2013),
which have been considered as diagnostic of the
genus Aristonectes (Otero et al. 2012,2014,2015b).
Europe
Seeley (1877) described a very large elasmosaurid
(BMNH 47295) from the Gault of Folkestone, England,
and identified it as Mauisaurus gardneri. The speci-
men, comprising cervical vertebrae and humerus, was
later referred to the genus Plesiosaurus by Lydekker
(1889). Welles (1962, p. 48) viewed the material as
indeterminate although it showed elasmosaurid affi-
nities; he considered the name to be a nomen vanum
(dubium).
Discussion
It now seems apparent that the hypodigm of Maui-
saurus, as modified by Welles and Gregg (1971) and,
most recently, by Hiller et al. (2005), includes more
than one taxon. The single significant autapomorphy
of Mauisaurus identified by Welles (1962) is the large
hemispherical capitulum on the femur. However, this
feature is now shown to be present in other taxa, ren-
dering Mauisaurus non-diagnosable. In addition, the
conical ventral midline process of the coracoids is
known in specimens that do not belong to Mauisaurus.
Indeed, a conical ventral process is also present in the
juvenile specimen SGO.PV.260 from the upper Maas-
trichtian of Chile, referred to A. quiriquinensis (Otero
et al. 2012,2014); It is likely present on the juvenile for-
mer holotype of ‘Tuarangisaurus?cabazai’Gasparini
et al. 2003 from the upper Maastrichtian of Argenti-
nean Patagonia, currently considered as an indetermi-
nate aristonectine (O’Gorman et al. 2014a). Finally, the
conical ventral process is present in Vegasaurus molyi,
from the lower Maastrichtian of Antarctica (O’Gorman
et al. 2015). Thus, the conical ventral process of the
coracoids is found to occur in aristonectines as well
as in non-aristonectine elasmosaurids, indicating that
this feature cannot be considered as reliable for
genus-level determinations
On the specimens used by Hiller et al. (2005) in their
description of M. haasti we can make the following
observations, including the locality from which each
was recovered and its age where determined.
DM R1529 remains the lectotype of M. haasti, but it
must be regarded as nomen dubium as the specimen is
not diagnosable. It is placed here as Elasmosauridae
indet. The femur, with a generally stocky morphology
and a hemispherical capitulum, bears a close resem-
blance to those of K. katiki and A. quiriquinensis,
suggesting a possible assignment to the Aristonectinae
(Otero et al. 2015a). However, the shapes of the epipo-
dials, being wider than long, indicate, in our opinion,
probable affinities to less derived elasmosaurids. The
specimen has been dated as Middle Campanian
(Wilson et al. 2005) Cheviot/Jed River (Figure 3).
CM Zfr 90 is an isolated left humerus, with associ-
ated radius and radiale (CM Zfr 88 and 89, respect-
ively). Heathstock, Waipara River area (Figure 3). It
could not be dated directly but is probably early Maas-
trichtian. This material shares with Kaiwhekea,More-
nosaurus,Kawanectes and Vegasaurus the
posterodistal extremity ending in an accessory facet
(Welles 1943;O’Gorman et al. 2015;O’Gorman
2016). These four genera were recovered as monophy-
letic by O’Gorman (2016) and therefore the presence of
this humeral morphology in New Zealand is consistent
with it.
CM Zfr 95 is a robust left femur that closely
resembles that of DM R1529 and may belong to the
same taxon but, coming from Birch Hollow, Waipara
River area (Figure 3), is probably younger (early Maas-
trichtian) although it could not be dated directly. It
should be placed as Elasmosauridae indet.
CM Zfr 102 comprises the anterior portion of a pair
of very large coracoids, regarded as the largest in a
growth series by Hiller et al. (2005). The features of
the specimen include a ventral conical process com-
monly observed in several austral elasmosaurids
(Sachs 2004; Hiller & Mannering 2005; Otero et al.
2012,2014;O’Gorman et al. 2013,2014b), allowing it
to be identified as Elasmosauridae indet. and the
large size might indicate an aristonectine affinity.
Weka Creek, Waipara River area (Figure 3). It could
not be dated directly.
CM Zfr 103 is the trunk and tail of a juvenile speci-
men. This is Hector’s(1874) specimen 1a, which Hut-
ton (1894) made the type of Cimoliasaurus caudalis
(nomen dubium). It was placed in M. haasti by Welles
and Gregg (1971). The cordiform intercoracoid vacuity
clearly indicates it belongs to the Elasmosauridae. This
has an additional historical value because it was the
first time that the cordiform vacuity, a highly diagnos-
tic feature of the Elasmosauridae (O’Keefe 2001; Ben-
son & Druckenmiller 2014), was described. Hiller
et al. (2005) used the coracoid as the smallest member
of their growth series. One interesting feature of this
specimen is the almost completely laterally directed
diapophyses, differing from the dorsolateral direction
observed in other elasmosaurids, such as Moreno-
saurus stocki (Welles, 1943), Elasmosauridae indet.
(AMNH 6796; Colbert 1949), Styxosaurus sp.
(AMNH 1495; Welles 1952;Otero 2016), among
NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS 7
others. A similar feature was recorded in Kawanectes
(O’Gorman 2016). Boby’s Stream, Waipara River area
(Figure 3); early Maastrichtian.
CM Zfr 104, recently described by O’Gorman et al.
(2014b), is an immature specimen comprising the
anterior part of the right coracoid, several vertebrae
(nine cervicals, one pectoral, eight posterior caudals)
and a number of bones from one limb. Based on the
proportions of the cervical vertebrae, O’Gorman et al.
(2014b) placed the specimen in the Aristonectinae.
Weka Creek, Waipara River area (Figure 3); early
Maastrichtian.
CM Zfr 115 was used by Hiller et al. (2005) as the
basis for a new description of M. haasti but, given
the results of recent research, it should be removed
from this taxon and placed elsewhere (see below). It
is a typical long-necked elasmosaurid with more than
65 cervical vertebrae. Ngaroma Station (Figure 3);
late Campanian.
KHM N 99–1079 is the part pelvis comprising ilium,
ischium and pubis of a very large individual. It can be
identified only as Plesiosauria indet. Haumuri Bluff
(Figure 3); middle Campanian.
The affinities of the Mauisaurus lectotype
The affinities of DM R1529 are difficult to assess
because of the scarcity of useful features in the speci-
men. The ilium is ventrally stocky, but no other feature
is observed (Figure 4). The pubis (Figure 4) is fragmen-
tary and the reconstruction provided by Hector (1874)
is probably quite speculative. The other preserved
elements belong to a hind limb (Figure 4) that shows
some interesting features:
Anterior and posterior knees. The development of
anterior and posterior knees (distal expansions), giving
a morphology very like that of a humerus, is very sur-
prising; femoral knees are usually less developed than
those of the humerus (Sato et al. 2006;O’Gorman
et al. 2015). However, a similar shape is observed in
A.quiriquinensis (Otero et al. 2014). The development
of a convex distal posterior expansion (knee) in Maui-
saurus is unusual as the posterior margins of femora
are usually straight, as in Hydrotherosaurus alexandrae
(Welles 1943, pl. 20d) and Callawayasaurus colombien-
sis (Welles 1962, pl. 4) or concave, as in Styxo-
saurus browni (Welles 1952,figure 7) and
Thalassomedon haningtoni (Welles 1952, figure 17).
Concave epipodial facets. The presence of concave
epipodial facets on the distal margin of the femur has
been recorded in other elasmosaurids such as Futaba-
saurus suzukii (Sato et al. 2006, figure 8D). They are
distinctly developed on the humeri of A. quiriquinensis,
but the femora have epipodial facets comparatively less
excavated. A very similar condition also occurs in
K. katiki.
Dorsally extended and posteriodistally directed tro-
chanter. The trochanter is almost completely visible
in dorsal view and diagonally disposed, as has been
recorded in the femora of K. katiki (Otero et al.
2015a, figure 2E), A. quiriquinensis (Otero et al.
2015a, figure 2A,C) and V. molyi (O’Gorman et al.
2015).
Hemispherical capitulum. The hemispherical capitu-
lum of the femur was considered the diagnostic feature
of M. haasti until the recognition of its presence among
the Aristonectinae (Otero et al. 2015a).
Articular facets for a pisiform between fibula and
fibulare. One of the most interesting features of the
M. haasti lectotype is the presence of a postaxial
notch between the fibula and fibulare. This feature
was also recorded in A. quiriquinensis (Otero et al.
2014, figure 16A) but has not been properly described
in other elasmosaurid hind limbs.
Epipodials comparatively short. DM R1529 has epi-
podials broader than long. Such proportions are com-
monly observed among Late Cretaceous elasmosaurids
from the northern Pacific (e.g. H. alexandrae Welles,
1943) and from the Western Interior Seaway (e.g.
S. browni Welles, 1952;H. alexandrae (Welles,
1943)). However, among known aristonectines preser-
ving enough complete limbs, the epipodials are longer
than broad, as occurs in K. katiki and A. quiriquinensis.
In early Late Cretaceous elasmosaurids such C. colom-
biensis Welles, 1962 and Thalassomedon haningtoni
Welles, 1943 the epipodials are also longer than broad.
DM R1529 shows some features that indicate aristo-
nectine affinities –hemispherical femoral head, fibula–
fibulare postaxial notch and diagonally disposed tro-
chanter –but other features indicate affinities closer
to the non-aristonectine elasmosaurids –short epipo-
dials. Therefore, it is possible that this specimen
belongs to a form that shows features intermediate
between the two groups, although a more accurate
determination is currently impossible.
Systematic palaeontology
Sauropterygia Owen, 1860
Plesiosauria de Blainville, 1835
Plesiosauroidea (Gray, 1825) Welles, 1943
Xenopsaria Benson & Druckenmiller, 2014
Elasmosauridae Cope, 1869
Tuarangisaurus sp.
(Figs. 6–12)
Mauisaurus haasti Hector, 1874: Hiller et al. 2005,
592–597, figs 6–17
Material
CM Zfr 115, a substantially complete skeleton compris-
ing a partial skull, most of the spinal column, bones
from all four limbs, and fragmentary remains of both
pectoral and pelvic girdles along with fragmentary
8N. HILLER ET AL.
ribs and gastralia. Numerous gastroliths accompany
the bones.
Formation and locality
Conway Formation; Ngaroma Station, on the Conway
River, North Canterbury (Figure 3). The site is high on
a hillside, scarred by numerous landslips (New Zealand
Fossil Record File number 032/f8862).
Age
Dinoflagellate cysts extracted from the rock adhering to
the plesiosaur bones indicate a late Campanian age for
the specimen (Wilson et al. 2005).
Collectors
As reported by Welles and Gregg (1971, p. 18), the
specimen was retrieved between November 1969 and
March 1970, by Messrs G. Warren (New Zealand Geo-
logical Survey), N. M. Hyde (Ngaroma Station),
R. W. Tyree (Christchurch) and S. P. Welles (Univer-
sity of California), with the assistance of various mem-
bers of the Warren, Hyde and Tyree families and
lodged in Canterbury Museum, Christchurch.
Taphonomy
CM Zfr 115 was preserved in a flat calcareous slab dis-
sected by many calcite veins. Removal of most of the
veins by weathering reduced the slab to a number of
small blocks that were subsequently separated by
movements of a landslip. Skull fragments and some
anterior cervical vertebrae were completely weathered
out of the matrix, but the rest of the skeleton was recov-
ered in the matrix, albeit in fragments. Final prep-
aration of the skeleton was achieved using
mechanical techniques because there was good separ-
ation of matrix from bone.
Although no attempt was made to reconstruct the
original relationships of the blocks after collection,
once preparation was complete, the bones were laid
out in what was believed to be their most likely resting
positions prior to burial. These indicated that the right
fore-paddle and left rear-paddle lay ventral side up and
the disarticulated left coracoid had come to lie behind
the right, with both displaced posteriorly. The other
limbs and caudal vertebrae were disassociated, with
no clear relation to the rest of the skeleton. The carcass
was interpreted as having come to rest on its right side
anteriorly, but from the sacral series posteriorly the
skeleton seems to have twisted so as to lie ventral
side up. Evidence of some scavenging was provided
by disruption of the skeleton and the presence of
three hexanchid shark teeth adjacent to the bones of
the right front paddle.
Description
The specimen CM Zfr 115 formed the basis of the last
attempt to understand Mauisaurus, presented by Hiller
et al. (2005) and it was described in detail in that pub-
lication. Only parts of that description are repeated
here, with some modification. In the vertebrae of the
cervical series and in the preserved caudals, the neural
arches are not firmly fused to their centra, whereas in
the dorsal vertebrae, neural arches and centra are
firmly fused. This situation leads us to interpret the
specimen as the skeleton of an individual that had
not reached full maturity at the time of death.
Skull remains (Figure 6). CM Zfr 115 preserves a par-
tial braincase comprising the incomplete basioccipital,
most of the basisphenoid and both exoccipital–
opisthotics (Figure 6D–G). It also preserves the right
dorsal ramus of the squamosal, which is joined to the
posterior part of the parietals (Figure 6A–C), and
part of the left lower jaw ramus, including the glenoid
(Figure 6H,I). The posterior width of the skull is esti-
mated at 140 mm based on the distance between the
midline and the exterior margin of the squamosal.
The basioccipital and basisphenoid are not fused.
The paroccipital processes of the exoccipital–opistho-
tics are incomplete, but were apparently short,
strap-like and directed downwards. The exoccipital–
opisthotics have foramina for the posterior cranial
nerves IX, X, XI exiting from the jugular foramen,
with XII emerging from a separate foramen behind
these (Hiller et al. 2005). Internally, there are distinct
foramina for the jugular (with IX, X) another for XI
and a third for XII (Figure 6J,K). There is a substantial
excavation for the fenestra ovalis (Figure 6J). The ver-
tical semi-circular canals are almost entirely in the
supraoccipital, with only small openings in the upper
surface of the exoccipital–opisthotics. The occipital
condyle is subcircular in outline and, in posterior
view, shows a slight depression along the dorsal margin
where a shallow circular notochordal pit is situated
(Figure 6D). The condyle arises solely from the body
of the basioccipital and a shallow groove separates it
from the rest of the basioccipital. Posteriolaterally,
the basioccipital bears subcircular facets for articula-
tion with the pterygoids. In posterior view (Figure
6D), the basioccipital appears asymmetrical below the
condyle with the right side extending further from
the condyle than the left. The left side may have suf-
fered some damage. The anterior surface of the basioc-
cipital bears a deeply pitted transversely ovoid facet for
contact with the basisphenoid. The basisphenoid,
which possesses a ventral keel, is broken on its anterior
face. It shows the course of the carotid arteries that
pierced the bone.
The right squamosal is represented by the dorsal
ramus, extending from the parietal suture to the
point where it sweeps forwards into the anterior
ramus. The left squamosal is represented only by its
dorsal-most portion immediately adjacent to the
NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS 9
parietal suture (Figure 6A–C). The squamosals are lat-
erally broad and axially compressed.
The parietals are represented by the posterior por-
tions only; the median suture between the two bones
is not clear and they seem to be firmly fused. The
ventromedial surfaces are heavily roughened for
attachment of the supraoccipital, and an irregular
ridge extends along the ventral midline where a suture
might be expected. The dorsolateral surfaces of the
parietals are gently concave and meet at an acute
angle to form a sharp sagittal crest (Figure 6C). The
crest bifurcates posteriorly and extends down each
squamosal as a sharp ridge. About one-third of the
way down the dorsal ramus, the ridge divides to
define the anterior margin of the dorsal ramus and
thence the dorsal margin of the anterior ramus, and
to separate the posterior surface of the dorsal ramus
from its lateral surface. The posterior surface of the
squamosal is marked by a series of grooves and
foramina.
The left lower jaw fragment (Figure 6H,I) is
c. 120 mm long and has very high lips to the glenoid
fossa, with the anterior lip being higher than the pos-
terior. The maximum vertical thickness of the jaw,
measured at the posterior margin of the glenoid is
only three-quarters that measured at the anterior
margin of the glenoid. The elements comprising this
part of the mandible are firmly fused and the sutures
between them are obscure.
Axial skeleton. In the previous description of
CM Zfr 115, Hiller et al. (2005) followed Carpenter
(1999) in not designating any vertebrae as pectorals.
In this account, we have chosen to recognise pectoral
vertebrae in the manner of Welles (1943), leading to
an apparent discrepancy in the cervical counts between
to two papers.
There are 63 vertebrae preserved in the neck region,
but no atlas or axis. As explained in Hiller et al. (2005,
p. 594), and judging by the relative size of the occipital
condyle and the first preserved cervical vertebra, we
believe that at least one more vertebra is missing
from the sequence; thus, a count of a minimum of 66
cervical vertebrae is likely. There are two pectoral ver-
tebrae, 18 dorsal vertebrae, three sacral vertebrae and at
least 20 caudals. Typical examples of each are shown in
Figure 7. The vertebrae were described in detail and fig-
ured by Hiller et al. (2005) when CM Zfr 115 was
regarded as belonging to Mauisaurus; that description
is not repeated here. A table of the dimensions of the
vertebrae and an analysis of their shapes were pre-
sented by O’Keefe and Hiller (2006).
Figure 6. CM Zfr 115 skull bones. A–C, preserved portions of parietal and right squamosal in A, right lateral; B, posterior view with
bilateral symmetry restored; C, dorsal view with bilateral symmetry restored. D–G, brain case elements. D, Basioccipital and exoc-
cipital–opisthotics in posterior view. E, Basioccipital in ventral view. F, Basisphenoid in ventral view (anterior towards top of page).
G, Basisphenoid in anterior view. H, I, Posterior of incomplete right lower jaw ramus in H, internal view, and I external view. J, Right
exoccipital–opisthotic in anterior view. K, Right exoccipital–opisthotic in medial view. a, angular; acc, ascending canal; agp, anterior
glenoid process; exop, exoccipital–opisthotic; f, foramina; fbo, facet for basioccipital; fenov, position of fenestra ovalis; feo, facet for
exoccipital; fso, facet for supraoccipital; gl, glenoid; gr, condylar groove; jfo, jugular foramen; npit, notochordal pit; oc, occipital
condyle; p, parietal; pgp, posterior glenoid process; ppr, paraoccipital process; ptf, pterygoid facet; ra, retroarticular process; sc,
sagittal crest; sq, squamosal; ut, depression for utriculus; vr, ventral ridge; (IX + X), posterior cranial nerves (glossopharyngeal
and vagus) emerge through jugular foramen; XI, foramen for cranial nerve XI (accessorius); XII, foramen for cranial nerve XII (hypo-
glossal). Cross-hatch shading indicates broken bone surface; open-circle shading indicates adhering sediment. Modified after Hiller
et al. 2005.
10 N. HILLER ET AL.
Limbs. Fragments of all four limbs are present in
CM Zfr 115. The right humerus has most of the shaft
and part of the head preserved, but the shaft has
been split lengthwise, and part of the distal end is miss-
ing (Figure 8A). The capitulum is gently convex with
an elliptical outline. It also shows the tuberosity to be
slightly prominent. The right femur is preserved in
two main parts, with a small portion of the diaphysis
missing. This bone has a strongly convex capitulum
with an almost circular outline (Figure 8B). The capitu-
lum is well separated and angled with respect to the rest
of the diaphysis. The trochanter is dorsally flattened.
The distal ends of both femora and humeri are dis-
tinctly angled, with clear non-concave facets for the
epipodials.
A reasonably well preserved right fore paddle
(Figure 9) shows an elongately ovoid epipodial fora-
men between the radius and ulna. Both epipodials are
significantly broader than long. Typical elasmosaurid
features in this paddle include the proximal row of
carpals comprising the radiale, centrale and ulnare;
the distal row made up of distal carpal I, fused distal
carpals II and III, and distal carpal IV. Metacarpal V
has been displaced to rest alongside both the distal car-
pal row and the row containing the other metacarpals
(O’Keefe 2001).
Girdles. The pectoral girdle of CM Zfr 115 includes
well-preserved scapulae, the right almost complete
and undistorted. This shows a typical triradiate struc-
ture (Figure 10), with the angle between the ventral
and dorsal rami, measured at the ridge on the ventral
surface where they meet, c. 130° (Figure 10). The dorsal
(ascending) ramus is high, with almost parallel sides
and a flat (‘square’rather than tapered) distal margin
(Figure 10). The remainder of the bone is thick, with
pockmarked surfaces for cartilaginous extensions on
the anteromedial surfaces.
The coracoids are fragmentary with much of their
mass missing and cannot be reconstructed accurately.
The anterior portions form the midline junction
between the paired coracoids; they are deep along the
midline, with an inverted V-shape in profile, suggesting
the presence of a transverse dorsal thickening and a
ventrally directed, blunt, conical process. Along the
midline each coracoid extends anteriorly into a blunt
process with a V-shaped notch between them.
Figure 8. CM Zfr 115 propodials. A, Right humerus. B, Right
femur.
Figure 7. Typical examples of vertebrae from different regions
of the spinal series. C44, mid-cervical; P1, first pectoral; D16,
posterior dorsal; S2, second sacral; Ca12, mid-caudal.
Figure 9. CM Zfr 115 right fore paddle in A, dorsal and B, ven-
tral views. ce, centrale; dc, distal carpal; ef, epipodial foramen;
mc, metacarpal; r, radius; re, radiale; ph, phalanx; u, ulna; ue,
ulnare. Arrows indicate the positions of hexanchid shark teeth.
NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS 11
As pointed out by Hiller et al. (2005), in no New
Zealand elasmosaurid specimen are there bones that
can be identified as clavicles or interclavicles. If these
elements were present in life, they probably were
never ossified.
The elements of the pelvic girdle are also fragmen-
tary in CM Zfr 115 and the detailed morphologies of
the component parts are not entirely clear. However,
pieces of what we interpret to be the right pubis and
right ischium (Figure 11) allow a partial description
to be made. The pubis is preserved in three fragments
that can be joined by aligning the few attached gastralia
and, although the contact between fragments has been
lost, the general outline of the bone can be observed. It
has a dorsoventrally deep ischial facet, with a concave
acetabular surface. It bears a rounded, anterolateral
prominence. There is a poorly developed symphyseal
contact; no posterior symphyseal extension is present.
The ischium is also preserved in three parts, one pre-
serving the pubic facet that precisely matches the
respective pubis contact. The two other fragments are
attached by matrix and show a rounded symphyseal
margin but any anterior extension has been lost, as
has the acetabular margin. The lack of broad symphy-
seal contact between the pubes and the ischia is consist-
ent with a subadult ontogenetic stage (Brown 1981).
Ribs and gastralia are too fragmentary for meaning-
ful description.
Comparisons
With other New Zealand elasmosaurids
Comparisons can be drawn between CM Zfr 115 and
several elasmosaurids described from New Zealand.
Of these, only one, Tuarangisaurus keyesi Wiffen &
Moisley, 1986, has been named; the others are rep-
resented by incomplete specimens that cannot be
fully diagnosed. CM Zfr 104 is a juvenile aristonectine
(O’Gorman et al. 2014b) possessing typical short cervi-
cal vertebrae that immediately separate it from
CM Zfr 115. CM Zfr 145 is an unusual form that Hiller
and Mannering (2005) believed could be separated
from all previously described elasmosaurids. In par-
ticular, its scapulae and coracoids show marked differ-
ences from the same bones in CM Zfr 115. In the latter,
the angle between the dorsal and ventral rami of the
scapula is 130°, the dorsal ramus has parallel sides
with a square termination. In CM Zfr 145 the angle
between dorsal and ventral rami is 140° and the dorsal
ramus tapers distally and has a rounded termination.
The coracoids of CM Zfr 145 are firmly fused anterior
of the intercoracoid vacuity unlike the situation in
CM Zfr 115 where the coracoids are separate. The cor-
acoids of CM Zfr 145 are flat and plate like with no sign
of the dorsal transverse thickening seen in CM Zfr 115
and on the ventral surface they bear a rod-like projec-
tion quite unlike the rounded conical ventral process of
CM Zfr 115.
CM Zfr 115 can be compared with the T. keyesi
holotype from Hawke’s Bay (Figure 3) insofar as they
have several anterior cervical vertebrae and several
skull bones in common. In comparing the skull
elements of CM Zfr 115 with those in T. keyesi (GNS
Figure 11. CM Zfr 115 right pubis and right ischium in dorsal
view.
Figure 10. CM Zfr 115 right scapula in medial view. cf, coracoid
facet; dr, dorsal ramus; gl, glenoid; sym, symphyseal surface; vr,
ventral ramus.
12 N. HILLER ET AL.
CD 425 and 426) (Figure 12), we can make the follow-
ing observations:
Squamosals: the squamosal of CM Zfr 115 is similar
to that of the T. keyesi holotype. Both specimens pre-
serve a right squamosal in which the dorsal ramus is
axially compressed. Also, in both specimens the squa-
mosals join dorsally in the midline forming a bulb. In
posterior view, both squamosals are remarkably simi-
lar, having a dorsal ramus with a flat posterior surface
and a cross-section with a conserved breadth that only
expands near the dorsal midline.
Parietals: even though the posterior part of the skull
of T. keyesi is crushed laterally it is possible to assess
that the parietals in each specimen are remarkably
similar. In both, the parietals form a low sagittal crest
with a flat dorsal surface having an axially extended tri-
angular outline.
Basioccipital: the basioccipital of T. keyesi is broken.
The portion anterior to the occipital condyle is still
attached in its anatomical position within the skull.
Even though this is laterally crushed, the basioccipital
contour does not reflect evident deformation. In pos-
terior view, the broken section of the T. keyesi basioc-
cipital shows a ventrally massive bone, twice as broad
as the dorsal portion where the occipital condyle is
expected to be attached. By comparison, the lateral
extension of the ventral basioccipital in CM Zfr 115
appears to be less expanded, which could reflect an ear-
lier ontogenetic stage. Because the T. keyesi basioccipi-
tal is posteriorly broken, it is difficult to evaluate the
shape of the pterygoidal articulation, only visible on
the right side of the CM Zfr 115 basioccipital.
The occipital condyle of T. keyesi is broken away,
making it impossible to compare it with that of
Figure 12. Comparison between skull fragments of CM Zfr 115 and the skull of Tuarangisaurus keyesi Wiffen and Moisley 1986 (GNS
CD 425, holotype). A, CM Zfr 115, right squamosal and part of the right parietal in right lateral view. B, GNS CD 425 in right lateral
view. Equivalent elements are digitally enhanced. C, CM Zfr 115, squamosals in occipital view. D, GNS CD 425, occipital view of the
skull, with the squamosals digitally enhanced. E, CM Zfr 115, occipital condyle and exoccipital–opistothics articulated, in occipital
view. F, Equivalent elements digitally enhanced on GNS CD 425 skull. G, GNS CD 426, anterior view of the atlantal cup of the atlas–
axis. The notochordal pit is visible, as it happens on the CM Zfr 115 occipital condyle, however, in the latter this has a comparatively
more dorsal position. H, GNS CD 425, dorsal view of the skull with posterior part of the sagittal crest and the squamosals digitally
enhanced for comparison. I, CM Zfr 115, sagittal crest and squamosals in dorsal view. ac, atlantal cup; boc, basioccipital; lexop, left
exoccipital-opisthotic; lppr, left paraoccipital process; lsq, left squamosal; npit, notochordal pit; oc, occipital condyle; rsq, right squa-
mosal; sc, sagittal crest.
NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS 13
CM Zfr 115. The outline of the atlantal cup of T. keyesi
is very similar to the occipital condyle outline of
CM Zfr 115, but in the latter, the notochordal pit lies
in the dorsal part of the condyle, whereas in the T. key-
esi atlantal cup, the notochordal pit appears to be in a
central position.
Basisphenoid: the basisphenoid of CM Zfr 115 is
separated from the rest of the braincase. Its preserved
length is near the same as the basioccipital excluding
the condyle. Ventrally, it possesses a sharp median
keel (Figure 6F). In T. keyesi, the basisphenoid is
obscured by matrix, however, O’Gorman et al. (2017)
have assessed its basisphenoid via computed tomogra-
phy scan. Interestingly, this also has a sharp ventral
keel, but the extension of the bone seems to be axially
larger. This could be the result of the combined length
of the basisphenoid and the anterior part of the
parasphenoid.
Exoccipital–opisthotics: these elements in CM Zfr 115
and T. keyesi are remarkably similar. In posterior view,
the T. keyesi skull allows us to observe a good deal of
the external surface of the left exoccipital–opisthotic.
Above the paraoccipital process, both specimens pos-
sess a slightly concave dorsolateral surface. Both also
have a visible suture that extends dorsoventrally over
their posterior surface, likely belonging to the contact
between opisthotic and the exoccipital. The paraoccipi-
tal process of both specimens is very similar, being ven-
trally recurved at c. 45°, having a short and
dorsoventrally compressed shaft with oval cross sec-
tion. In the T. keyesi holotype, the distal end of its
left paraoccipital process is broken, suggesting the pres-
ence of a shaft slightly larger than that of CM Zfr 115.
Such a difference could be expected due to the different
ontogenetic stages of the specimens.
Mandibular rami: CM Zfr 115 only preserves a pos-
terior part of the left ramus. This includes the retroar-
ticular process, the glenoid, part of the coronoid and a
posterior fragment of the dentary. Regrettably, both
rami of T. keyesi are broken just after the end of the
dentition, being absent a good deal of the coronoid
(part of it is obscured by matrix), while the glenoid
and retroarticular processes are lost. The rami of
both specimens share the presence of bowed mandibles
in ventral view, however, this is a trait typical of most
elasmosaurids (O’Keefe 2001).
Wiffen and Moisley (1986) attributed a small sec-
tion of a left angular, quadrate and squamosal
(GNS CD 426) to the holotype of T. keyesi and these
can be compared with CM Zfr 115. These show that
the lower jaw glenoids of both CM Zfr 115 and Tuar-
angisaurus have enlarged glenoid processes, with the
anterior one being higher than the posterior, although
this feature is more marked in CM Zfr 115.
In addition to the skull elements, both CM Zfr 115
and the T. keyesi holotype show comparable characters
in the neck, such as the anterior and posterior
zygapophyses becoming conjoined from about the
ninth or tenth cervical vertebra posteriorly, but their
vertebral length indices (Brown 1981) differ (Table
4). Although we cannot be certain about the serial pos-
ition of the cervical vertebrae in CM Zfr 115, it appears
that it has consistently lower values (c.101 vs. 113) for
the first seven preserved centra other than atlas and
axis. The significance of this difference is uncertain
and it may be accounted for by ontogenetic differences
between the holotype of T. keyesi, a somewhat more
mature animal (judging by the comparatively larger
skull elements that the two specimens have in com-
mon), and the subadult CM Zfr 115. Brown (1981,
p. 269 and figure 13) has shown that vertebral indices
change during ontogeny.
In addition to the vertebral length indices (Brown
1981) analysed above, the cervical vertebrae of the
T. keyesi holotype and those of CM Zfr 115 share sev-
eral morphological traits. In articular view, both speci-
mens have neural pedicels that are thin and high,
leaving a dorsoventrally extended, oval neural canal.
Both also share the presence of prezygapophyses
slightly broader than the neural arch. In lateral view,
the cervical centra of both specimens have lateral
keels. The few preserved neural spines in CM Zfr 115
allow us to assess that the prezygapophyses of both
specimens similarly extend beyond the articular faces
of their respective centra. Although these traits are
not diagnostic at genus level, and are typical of austral,
non-aristonectine elasmosaurids (Hiller et al. 2005),
the cervical features of both specimens suggest close
affinities between them.
Comparison with other Late Cretaceous
Weddellian elasmosaurids
The features of the axial skeleton and limbs of
CM Zfr 115 differ from those of the aristonectines. In
particular, the vertebral proportions of CM Zfr 115
Table 4. Vertebral length index (VLI) for the anterior cervical
vertebrae (excluding atlas and axis) for CM Zfr 115 (N) and
Tuarangisaurus (GNS CD 426; T). VLI is calculated as L/D ×
100, where L = mid ventral centrum length and D = posterior
average centrum diameter (Brown 1981). Lack of data is
indicated by —. The vertebra number for CM Zfr 115 is the
number of the preserved centrum as explained in Hiller et al.
(2005); for Tuarangisaurus the vertebra number represents
the actual place occupied in the series by the centrum,
where atlas and axis are 1 and 2, respectively.
Vertebra
number
Length
(mm)
Height
(mm)
Breadth
(mm) VLI (%)
NTNTNTNT N T
C13263823293136 96117
C2 4 31 36 25 29 36 39 102 106
C3 5 32 39 25 30 36 40 105 111
C4 6 33 40 26 29 39 42 102 113
C5 7 34 40 26 27 40 41 103 118
C6 8 35 42 28 30 43 43 100 115
C7 9 35 –27 –42 42 101 –
Average 101 113
14 N. HILLER ET AL.
indicate relatively longer and narrower centra than
found among the aristonectines (Cruickshank & For-
dyce 2002; Gasparini et al. 2003; Otero et al. 2014).
In addition, the ulnae and radii of aristonectines are
longer than wide (Otero et al. 2014), contrary to the
situation in CM Zfr 115.
The features of CM Zfr 115 also differ from the two
non-aristonectines known from the Weddellian Pro-
vince, V. molyi O’Gorman et al. 2015 and Kawanectes
lafquenianum (Gasparini and Goñi) O’Gorman, 2016.
CM Zfr 115 has a cervical vertebral count of at least
65 elements, while V. molyi has only 54 cervicals
(and 3 versus 2 pectorals). Vegasaurus molyi also has
a scapular ridge (O’Gorman et al. 2015, figure 8B,C),
a feature not seen in the New Zealand specimen. Kawa-
nectes lafquenianum differs from CM Zfr 115 in the
greater lateral extension of its caudal parapopyses
(O’Gorman 2016).
Comparison with North American Late Cretaceous
elasmosaurids
The axial formula of CM Zfr 115 indicates c. 66 cervical
vertebrae present, with the possibility that there may
have been as many as 68 originally. This allows us to
reject close relationships with taxa such as Elasmo-
saurus platyurus Cope, 1869 and Albertonectes vander-
veldei Kubo et al. 2012, which are characterised by
possessing more than 70 cervical vertebrae. All other
described forms have fewer cervical vertebrae than
CM Zfr 115.
In addition, CM Zfr 115 does not possess elongated
centra in the mid-cervical region (the so-called can-
shaped centra of Otero (2016)) like those present in
E. platyurus,Albertonectes vanderveldei,Terminonata-
tor pointeixensis Sato, 2003,Styxosaurus browni
Welles, 1943 (AMNH 5385) and Styxosaurus sp.
(AMNH 1495). Therefore, all these taxa can be distin-
guished from CM Zfr 115.
CM Zfr 115, and the holotype of T. keyesi, have a
posteriorly flat squamosal arch, while the squamosal
shaft is dorsoventrally thicker than axially long. This
contrasts with the squamosal arches of Thalassome-
don haningtoni Welles, 1943 and Styxosaurus spp.,
which have an anteriorly directed embayment in dorsal
view (Welles 1943,1952;Carpenter 1999). Interest-
ingly, a straight squamosal arch (in dorsal view) is
also present in C. colombiensis Welles, 1962 and in
H. alexandrae Welles, 1943. However, the anterior cer-
vical vertebrae of C. colombiensis are very different
from those of CM Zfr 115 in having a near circular
articular facet without a ventral notch (Welles 1962:
plate 3c). Also, the radius and ulna are longer than
wide in the Albian C. colombiensis (Welles 1962)
whereas those of CM Zfr 115 are wider than long.
H. alexandrae differs from CM Zfr 115 in having
fewer cervical vertebrae and it shares with CM Zfr 115
and with the T. keyesi holotype the formation of a
dorsal triangular prominence at the squamosal midline
contact (Welles 1962: figure 4; this study: Figure 12).
Although these taxa could be closely related, they are
different.
The discussion above shows that the closest affi-
nities of CM Zfr 115 are to be found with the holotype
of T. keyesi. Overlapping of the skull bones of T. keyesi
and CM Zfr 115 (Figure 12) is restricted to only a few
portions of the posterior braincase and the mandibles.
Even though these do not preserve reliable diagnostic
elements among elasmosaurids, there are obvious
very close morphological similarities between the two
specimens. The shape of the squamosals and the exoc-
cipital-opisthotics are very alike, as are the anterior cer-
vical vertebrae; the minor differences that do occur
probably reflect the different ontogenetic stage of
each specimen. All these facts strongly suggest that
they could belong to closely related taxa, probably the
same genus, if not the very same species.
The question arises as to how comparable in age
Tuarangisaurus and CM Zfr 115 might be. We know
that the latter can be dated to the upper Isabelidi-
nium pellucidum zone of Wilson et al. (2005) but,
unfortunately, Tuarangisaurus has not been dated
directly. However, Young and Hannah (2010) studied
the dinoflagellate biostratigraphy of the Maungatani-
wha Sandstone of northwest Hawke’s Bay, New Zeal-
and, the lithological unit from which Tuarangisaurus
was derived. They concluded that the plesiosaurian-
bearing calcareous concretions from this unit exhibited
a range of ages, from lower to upper Haumurian (early
Campanian to early Maastrichtian), spanning the
entire age range of the formation, i.e. from the Satyro-
dinium haumuriense (Vozzhennikovia spinulosa sub-
zone)–I. pellucidum zones. It is therefore quite
feasible that Tuarangisaurus and CM Zfr 115 are
about the same age but, equally likely, Tuarangisaurus
may be slightly older than CM Zfr 115.
Conclusions
For well over a century, the species Mauisaurus haasti
has been considered a very strange austral elasmo-
saurid with obscure affinities due to the incompleteness
of its lectotype (DM R1529). Additional specimens,
later referred to the same species, are currently
shown to belong to taxa different from DM R1529.
As a consequence, the name Mauisaurus haasti Hector
should be applied only to the lectotype of the species,
DM R1529, and it should be regarded as a nomen
dubium as the species cannot be adequately diagnosed,
although it does show possible affinities with the Sub-
family Aristonectinae. Thus, it is recommended here
that further usage of the genus and species M. haasti
be abandoned.
Specimen CM Zfr 115, a typical long-necked elas-
mosaurid at one time believed to belong in Mauisaurus
NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS 15
(Hiller et al. 2005), can now be regarded as closely
comparable to T. keyesi. CM Zfr 115 and the holotype
of T. keyesi are shown to be very similar in many
respects and both specimens share a common biogeo-
graphic and stratigraphic occurrence. This leads us to
conclude that CM Zfr 115 can be placed in Tuarangi-
saurus. However, the former lacks some important
elements of the latter, so we prefer to leave it in open
nomenclature.
Acknowledgements
The authors are grateful to the directors and curatorial staff
of the following New Zealand institutions for allowing access
to Mauisaurus specimens in their care: Museum of New
Zealand Te Papa Tongarewa, Wellington; Canterbury
Museum, Christchurch; GNS Science, Lower Hutt. We are
also grateful to anonymous reviewers whose comments
prompted us to substantially improve the manuscript.
Associate editor: Professor Kathy Campbell.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
RAO’s work is supported by the U-REDES grant (Domeyko
II UR-C12/1, Universidad de Chile). JPO’G’s work is sup-
ported by PICTO 2010-0093 PICT 2012-0748; PIP 0433,
UNLP N 677 and UNLP N607
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