Content uploaded by Jun Liu
Author content
All content in this area was uploaded by Jun Liu on Jun 26, 2014
Content may be subject to copyright.
Can. J. Earth Sci. 42: 2081–2086 (2005) doi: 10.1139/E05-076 © 2005 NRC Canada
2081
Rostral structure in Thalattosauria (Reptilia,
Diapsida)
Olivier Rieppel, Johannes Müller, and Jun Liu
Abstract: The rostral structure of thalattosaurs is reviewed on the basis of a re-investigation of the holotype of
Nectosaurus halius and Thalattosaurus alexandrae. The askeptosaurid genera Askeptosaurus and Anshunsaurus share an
elongated, parallel-sided rostrum that terminates in a blunt tip. A diastema separating the premaxillary from the
maxillary teeth is absent. The claraziid genera Clarazia and Thalattosaurus share a relatively shorter rostrum that has
convergent lateral margins and that terminates in a pointed tip. A diastema separating the premaxillary from the
maxillary teeth is present. The well-preserved holotype of Nectosaurus halius shows a highly derived rostral structure.
The maxilla is short with an anteriorly truncated (vertical) margin, a narrow but high ascending process, and a dorsally
curving medial flange that is in natural articulation with the ventrally deflected vomer. These findings corroborate
Peyer’s original reconstruction of Hescheleria with a nearly vertically placed premaxilla.
Résumé : La structure rostrale des thalattosaures est revue à la lumière d’un nouvel examen des holotypes de Necto-
saurus halius et de Thalattosaurus alexandrae. Les genres d’askeptosauridés Askeptosaurus et Anshunsaurus partagent
un rostre allongé aux parois parallèles se terminant en une extrémité arrondie. Les genres claraziidés Clarazia et
Thalattosaurus partagent quant à eux un rostre plus court dont les bordures latérales sont convergentes et qui se
termine en une pointe fine. Un diastème séparant les dents prémaxillaires des dents maxillaires est également présent.
L’holotype de Nectosaurus halius, qui est bien préservé, présente une structure rostrale hautement dérivée. La maxille
est courte et montre une bordure tronquée antérieurement (verticale), un processus ascendant étroit mais haut et une
bordure médiale inclinée dorsalement qui forme une articulation naturelle avec le vomer dévié ventralement. Ces
observations viennent appuyer la reconstitution initiale d’Hescheleria par Peyer qui présentait une prémaxille quasi
verticale.
[Traduit par la Rédaction] Rieppel et al. 2086
Introduction
Thalattosaurs are a monophyletic clade of Triassic marine
reptiles (Nicholls 1999) of uncertain neodiapsid affinities
(Rieppel 1987, 1998; Müller 2004), known from the Middle
and Late Triassic of Europe, southern China (Guizhou Prov-
ince), and western North America. The first thalattosaurs to
be described were Thalattosaurus and Nectosaurus from the
Upper Triassic of California (Merriam 1904, 1905, 1908).
This material was recently reviewed by Nicholls (1999). Rather
fragmentary thalattosaur material (Thalattosaurus, Paralonectes,
Agkistrognathus) was reported from the Lower to Middle
Triassic Sulphur Mountain formation of eastern British
Columbia (Nicholls and Brinkman 1993), while other frag-
mentary specimens were collected in the Upper Triassic
Pardonet Formation of northeastern British Columbia (Storrs
1991). New thalattosaur material from the Triassic of north-
western Nevada remains currently undescribed.
Peyer (1936a, 1936b) described two thalattosaur genera
(Clarazia, Hescheleria) from the Middle Triassic of Monte
San Giorgio (southern Switzerland, southern Alps) that were
re-described by Rieppel (1987). A third thalattosaur from the
Monte San Giorgio, Askeptosaurus, was described by Kuhn
(1952) and Kuhn-Schnyder (1971), who also commented on
thalattosaur anatomy and relationships in a general sense
(Kuhn-Schnyder 1988). Renesto (1991) described Endenna-
saurus from the Upper Triassic of Lombardy, Italy, and referred
it to thalattosaurs, an interpretation that was corroborated in
a recent study by Müller et al. (2005).
Anshunsaurus huangguoshuensis was the first thalattosaur
to be described from the early Late Triassic of southwestern
China (Liu 1999). Only the skull of the holotype has been
Received 23 February 2005. Accepted 29 June 2005. Published on the NRC Research Press Web site at http://cjes.nrc.ca on
3 February 2006.
Paper handled by Associate Editor H.-D. Sues.
O. Rieppel.1Department of Geology, The Field Museum, 1400 S Lake Shore Drive, Chicago, IL 60605–2496, USA.
J. Müller. Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Rd. N., Mississauga, ON L5C 1C6, Canada.
J. Liu. Lamont-Doherty Earth Observatory, Columbia University, Palisade, New York, NY 10964, USA.
1Corresponding author (e-mail: orieppel@fieldmuseum.org).
© 2005 NRC Canada
2082 Can. J. Earth Sci. Vol. 42, 2005
described so far, and only in dorsal view (Rieppel et al.
2000). The postcranial skeleton of the holotype, as well as
additional specimens of Anshunsaurus, remain undescribed.2
The second thalattosaur genus from China is known to include
two species, viz. Xinpusaurus suni (Yin et al. 2000; see also
Liu and Rieppel 2001; Luo and Yu 2002), and Xinpusaurus
bamaolinensis (Cheng 2003, see also Jiang et al. 2004).
Thalattosaur interrelationships were analyzed by Nicholls
(1999), Rieppel et al. (2000), Liu and Rieppel (2001), Jiang
et al. (2004), Müller (2005), and Müller et al. (2005). The
studies by Liu and Rieppel (2001), Jiang et al. (2004), and
Müller (2005) in particular highlighted the potentially interesting
hypothesis that the southern Chinese genus Xinpusaurus
might share trans-Pacific relationships with Nectosaurus and
Paralonectes from western North America. This hypothesis
was, in large part, based on rostral structure, as Xinpusaurus
was believed to share with Nectosaurus and Paralonectes a
unique structure of the maxilla and dentary, which show a
dorsal curvature in their anterior part. However, a recent review
of the material of Thalattosaurus and Nectosaurus at the
University of California Museum of Paleontology at Berkeley
(UCMP) revealed a misinterpretation of the rostral structure
that has misled previous analyses. The purpose of this paper
is to describe and (or) revise the rostrum morphology in cur-
rently known thalattosaurs as a step towards an improved
character database for phylogenetic analyses. These will also
have to take into account the thalattosaur material currently
under study.
Rostral structure in thalattosaurs
Thalattosaurs in general are characterized by an elongated
rostrum formed mostly by the premaxillae, which results in
retracted external nares in these marine reptiles. Three
distinctive rostral patterns can be recognized among thalatto-
saurs.
Askeptosaurus is a relatively large thalattosaur of at least
2.5 m total length (Kuhn 1952) with a distinctive skull structure
(Müller 2005). The rostrum is much elongated: the distance
from the anterior margin of the orbit to the tip of the snout
exceeds the distance from the anterior margin of the orbit to
the posterior end of the parietal. The rostrum is slender, with
more or less parallel lateral edges, and it terminates in a
blunt tip. No distinct diastema exists between the premaxillary
and maxillary teeth. The same general type of rostral structure
is shared by Anshunsaurus from southern China (Rieppel et
al. 2000), although in this taxon the anterior tapering of the
rostrum may be slightly more pronounced, and the anterior
tip of the rostrum slightly more pointed.
The rostral structure of Endennasaurus (Müller et al. 2005)
is similar to that of Askeptosaurus and Anshunsaurus with
regard to the significant elongation of the rostrum and the
lack of an anteroventral curvature. In contrast to the above-
mentioned taxa, however, the rostrum does not possess par-
allel lateral edges; the margins rather converge towards the
tip of the snout. Thus, the rostrum is anteriorly very pointed
and sharp. In addition, Endennasaurus is unique in lacking
any dentition.
Clarazia shows a distinctly different rostral structure
(Rieppel 1987). The rostrum is not as long relative to the
postorbital region of the skull as it is in Askeptosaurus and
Anshunsaurus, and although it is broad posteriorly, it tapers
to a narrow, pointed tip anteriorly. This results in convergent,
rather than parallel, lateral edges of the snout. Furthermore,
the anterior tip of the rostrum is slightly deflected ventrally,
Fig. 1. The rostrum of Thalattosaurus alexandrae. (A) holotype
(UCMP 9085) in right lateral view; (B) semidiagrammatic recon-
struction (based on Nicholls 1999, Fig. 14A). d, dentary; f, frontal;
m, maxilla; n, nasal; pm, premaxilla; prf, prefrontal.
Fig. 2. Reconstruction of the skull of Hescheleria ruebeli (the jugal
is modeled on Nectosaurus). d, dentary; ju, jugal; m, maxilla;
n, nasal; pm, premaxilla; pof, postorbitofrontal; prf, prefrontal.
2J. Liu and O. Rieppel. Restudy of Anshunsaurus huangguoshuensis (Reptilia: Thalattosauria) from the Middle Triassic of Guizhou, China.
In preparation. O. Rieppel, C. Li, and J. Liu. A new species of the thalattosaur genus Anshunsaurus (Reptilia: Thalattosauria) from the Mid-
dle Triassic of Guizhou Province, southwestern China. In preparation.
© 2005 NRC Canada
Rieppel et al. 2083
overhanging the anterior tip of the mandible. A distinct
diastema separates the premaxillary from the maxillary teeth.
Thalattosaurus is larger than Clarazia, but shares the
same rostral structure. As noted by Merriam (1905, p. 8), the
skull of the holotype of Thalattosaurus alexandrae (UCMP
9085) was preserved in four pieces, three of which constitute
the rostrum. These pieces were originally connected by wide
calcite vein-filled cracks, but were separated during prepara-
tion. Alignment of the four pieces requires that the gaps
formed by the vein-filled cracks are accounted for in the re-
construction of the rostrum. If properly aligned, the rostrum
appears to indicate a dorsal curvature of the anterior end of
the maxilla, whereas the anterior end of the premaxilla is de-
flected ventrally. However, the prefrontal descends ventrally
to a level well below the apparent ventral margin of the
maxilla, where it contacts the anterior tip of the suborbital
process of the jugal (Nicholls 1999). This is certainly an un-
natural relation of the prefrontal and maxilla, which indi-
cates that the alveolar margin of the posterior part of the
maxilla is not preserved. A line drawn from the preserved
anterior alveolar margin of the maxilla to the lower edge of
the prefrontal shows that the ventral margin of the maxilla
was straight, matching the straight dorsal margin of the den-
tary. Therefore, the rostral structure is similar to that seen in
Clarazia, i.e., a straight alveolar margin of the maxilla and a
slightly ventrally deflected premaxillary rostrum that over-
hangs the anterior tip of the dentary, which itself is deflected
ventrally to a slight degree (Fig. 1).
Xinpusaurus shares a similar rostral structure, although it
is autapomorphic in that the alveolar margin shows a distinct
dorsal curvature at the anterior end of the maxilla, which re-
sults in a procumbent orientation of the anterior maxillary
teeth. This is matched by a corresponding dorsal curvature
of the alveolar margin of the dentary with teeth that point
backwards. Xinpusaurus also lacks a diastema between the
premaxillary and maxillary teeth. X.bamaolinensis differs
from X. suni and other thalattosaurs not only in overall size,
but also in the much elongated premaxilla that projects well
beyond the anterior tip of the dentary (Cheng 2003).
All the thalattosaur genera discussed so far have a rela-
tively elongate maxilla with a broad based ascending process.
The ascending process has a rather gentle anterior slope, but
may have a more steeply oriented posterior slope.
The rostrum of Hescheleria is less easily interpreted,
however. The skull is disarticulated, but the maxilla and
premaxilla are well preserved and easily identified (Peyer
1936b; Rieppel 1987). The maxilla in this taxon is much
shorter than in all the other taxa discussed in the preceding
paragraphs. It has a narrow based ascending process with a
steep anterior slope and a distinctly concave posterior margin.
The posterior end of the maxilla is tapering and carries a
facet for the anterior tip of the suborbital process of the
jugal. The anterior end of the maxilla is short and terminates
in a relatively high, vertically oriented margin. Given the
generally excellent preservation of the fossils from the
Grenzbitumen horizon of Monte San Giorgio, and the identical
preservation of both maxillae in Hescheleria, the abrupt
anterior termination of the maxilla is unlikely because of
breakage.
The premaxilla of Hescheleria (Fig. 2) is relatively large,
much larger than the maxilla, and distinctly curved. Poste-
riorly, it carries two distinct processes. The ventral one
formed the ventral margin of the external naris and con-
tacted the anterior end of the maxilla. The larger dorsal (na-
sal) process formed the anterior and dorsal margin of the
external naris and most likely contacted the frontal.
Aligning the posterior ventral process of the premaxilla
with the anterior end of the maxilla results is a very strange
position of the first element. The premaxilla would be verti-
cally oriented, almost at a right angle relative to the horizontal
alveolar margin of the maxilla (Peyer 1936b, text fig. 1).
Rieppel (1987) found Peyer’s (1936b) reconstruction of the
rostrum of Hescheleria not convincing on functional grounds
and invoked postmortem deformation of the bone to fit the
Fig. 3. The rostrum of Nectosaurus halius (holotype, UCMP 9124) in left lateral (A) and right lateral (B) views. m, maxilla; p.as.,
ascending process of maxilla; pm, premaxilla; v, vomer.
© 2005 NRC Canada
2084 Can. J. Earth Sci. Vol. 42, 2005
premaxilla to a more horizontal position relative to the maxilla,
in a reconstruction that resembles the rostrum of Clarazia.
The snout of Nectosaurus halius (UCMP 9124, holotype;
Figs. 3, 4) was prepared using acid and described by Nicholls
(1999). The maxilla is a relatively short element with a ta-
pering posterior tip, a narrow based, tall, and pointed as-
cending process with a distinctly concave posterior margin,
and an abrupt anterior end (Fig. 3). While some breakage
may have occurred at the anterior end of the maxilla, as
indicated by Nicholls (1999), it is not likely to have been ex-
tensive because the structure of the bone recalls that seen in
Hescheleria. Interestingly, there is a third thalattosaur that
Fig. 4. The rostrum of Nectosaurus halius (holotype, UCMP 9124) in dorsal (A) ventral (B), and frontal (c) views. gr.ns., groove for
nasal septum; m, maxilla; pm, premaxilla; v, vomer.
© 2005 NRC Canada
Rieppel et al. 2085
shares the same general form of the maxilla, namely the
specimen referred to Paralonectes by Nicholls and Brink-
man (1993, fig. 4), even though preservation renders the
alignment of the anterior alveloar margin difficult to assess.
In front of and above the maxillae of Nectosaurus (UCMP
9124) was located, in the limestone, a distinctly curved bar
of bone that represents the posterior part of the broken
posterior dorsal (nasal) process of the premaxilla (Nicholls
1999). In between the maxillae is located the distinctly curved
vomer that carries teeth on its anterior part (Nicholls 1999).
The anterior, ventrally directed part of the vomer extends be-
yond the level of the alveolar margin of the maxilla, and
hence is exposed in lateral view. The posterior dorsal flanges
of the vomer emerge from behind the ascending processes of
the maxillae (Nicholl 1999, fig. 18).
The vomers are fused anteriorly, but retain paired posterior
tips (Fig. 4B; Nicholls 1999, fig. 20). From those posterior
tips rise vertically ascending dorsal flanges, which merge
anteriorly to form a distinct, V-shaped groove on the dorsal
surface of the vomer (Nicholls 1999, fig. 18A), which may
have supported the anterior end of the internasal septum
(Fig. 4C). There are five teeth located on the anterior part of
the vomer, one anteromedial tooth and two lateral ones on
either side (Nicholls 1999, fig. 20). From each maxilla origi-
nates a medial palatal shelf that extends towards the vomer,
thus forming the gently curved anterior margin of the inter-
nal naris. The contact between the right maxilla and the
vomer is broken, but on the left side the two elements are
preserved in perfect articulation (Figs. 4A, 4B). The medial
margin of the palatal shelf of the maxilla is turned upwards,
and is smoothly applied against the lateral surface of the
dorsally projecting wings of the vomer. This natural contact
indicates a strong ventral deflection of the vomer, corresponding
to a vertical ventral deflection of the rostrum as was recon-
structed for Hescheleria by Peyer (1936b, fig. 2).
Discussion
The vertically descending premaxillary rostrum is a unique
morphology shared by Hescheleria and Nectosaurus, perhaps
also Paralonectes, amongst known thalattosaurs. The recon-
struction of the skull of Paralonectes by Nicholls and Brinkman
(1993, fig. 7) shows an unnatural maxillary–premaxillary
contact, which is reconciled if a vertically descending pre-
maxilla is assumed. Liu and Rieppel (2001) used a dorsal
curvature of the anterior end of the alveolar margin of the
maxilla as a potential synapomorphy shared by Xinpusaurus,
Nectosaurus, and Paralonectes, indicating the potential of
trans-Pacific relationships among these three genera. On the
basis of the new interpretation of the thalattosaur rostrum
presented here, the dorsal curvature of the anterior end of the
maxillary alveolar margin is autapomorphic for Xinpusaurus
and hence uninformative for phylogenetic analysis. Conversely,
the unique rostral morphology is suggestive of potential rela-
tionships of Hescheleria from the western Tethyan faunal
province with Nectosaurus and Paralonectes from the eastern
Pacific faunal province. However, both Hescheleria and
Fig. 5. Rostrum morphology in thalattosaurs: (A) Askeptosaurus
italicus (the lateral view of the rostrum in Anshunsaurus huangguo-
shuensis and Anshunsaurus n. sp. remains to be described, but
closely approaches that of Askeptosaurus); (B) Thalattosaurus
alexandrae (the rostrum is not preserved in lateral view in Clarazia
schinzi, but is assumed to approach that of Thalattosaurus);
(C) Xinpusaurus suni;(D)Hescheleria ruebeli (the orientation
of the premaxilla in this reconstruction is determined by its contacts
with the maxilla and nasal); (E) Nectosaurus halius (the orientation
of the premaxilla in this reconstruction is determined by the position
of the vomer). The rostrum of Paralonectes is not preserved in lateral
view, but might approach the profile seen in Hescheleria and
Nectosaurus, or alternatively that of Xinpusaurus.
© 2005 NRC Canada
2086 Can. J. Earth Sci. Vol. 42, 2005
Nectosaurus are known from very fragmentary material only,
while other thalattosaur material (e.g., of Anshunsaurus) still
remains undescribed. An improved and comprehensive phylo-
genetic analysis of thalattosaur relationships should include
material currently under study. But in the meantime, we offer
the following character definitions that relate to rostrum mor-
phology (Fig. 5) and that can be included in future analyses
of thalattosaur interrelationships:
(1) Rostrum elongation: distance from the anterior margin
of the orbit to the anterior tip of the rostrum less (0), or
more (1), than twice the distance from the anterior margin
of the orbit to the posterior margin of the parietal skull
table.
(2) Rostrum shape: lateral edges of rostrum parallel, rostrum
terminating in a blunt tip (0); lateral edges of rostrum
converging, rostrum terminating in a pointed tip (1).
(3) Rostrum profile: rostrum straight (0); premaxilla moder-
ately turned downwards (1); premaxilla strongly turned
downward, its alveolar margin positioned nearly vertically
relative to the alveolar margin of the maxilla (2).
(4) Maxilla alveolar margin: straight (0); curved upwards at
anterior end of maxilla (1). This is currently an autapo-
morphy of Xinpusaurus, but could potentially be a char-
acter found to be shared with Paralonectes pending the
discovery of better preserved material (see Nicholls and
Brinkman 1993, fig. 7).
(5) Proportions of maxilla: maxilla at least twice as long as
high (0); maxilla short, approximately as long as high,
with truncated anterior end and narrow, vertically
positioned ascending process.
Acknowledgments
We thank Kevin Padian for generous access to the thalatto-
saur material kept at the University of California Museum of
Paleontology, Berkeley, California. Donald Brinkman and
Susan Evans, Betsy Nicholls and Hans-Dieter Sues kindly
reviewed various versions of this paper, offering much helpful
advice and criticism. Studies of J.M. in Berkeley were finan-
cially supported by the Samuel P. Welles Fund, as well as by
the Studienstiftung des deutschen Volkes.
References
Cheng, L. 2003. A new species of Triassic Thalattosauria from
Guanling, Guizhou. Geological Bulletin of China, 22: 274–277.
Jiang, D.A., Maisch, M.W., Sun, Y.-L., Matzke, A.T., and Hao,
W.C. 2004. A new species of Xinpusaurus (Thalattosauria) from
the Upper Triassic of China. Journal of Vertebrate Paleontology,
24: 80–88.
Kuhn, E. 1952. Die Triasfauna der Tessiner Kalkalpen. XVII.
Askeptosaurus italicus Nopcsa. Schweizerische Paläontologische
Abhandlungen, 69, pp. 1–52.
Kuhn-Schnyder, E. 1971. Über einen Schädel von Askeptosaurus
italicus Nopcsa aus der Mittleren Trias des Monte San Giorgio
(Kt. Tessin, Schweiz). Abhandlungen des hessischen Landesamtes
für Bodenforschung, 60: 89–98.
Kuhn-Schnyder, E. 1988. Bemerkungen zur Ordnung der Thalatto-
sauria (Reptilia). Eclogae geologicae Helvetiae, 81: 879–886.
Liu, J. 1999. New discovery of sauropterygian from Triassic of
Guizhou, China. Chinese Science Bulletin, 44: 1312–1315.
Liu, J., and Rieppel, O. 2001. The second thalattosaur from the
Triassic of Guizhou, China. Vertebrata PalAsiatica, 39: 77–87.
Luo, Y., and Yu, Y. 2002. The restudy on the skull and mandible of
Xinpusaurus suni. Guizhou Geology, 19: 71–75.
Merriam, J.C. 1904. A new marine reptile from the Triassic of
California. University of California Publications, Bulletin of the
Department of Geology, 3: 419–421.
Merriam, J.C. 1905. The Thalattosauria, a group of marine reptiles
from the Triassic of California. Memoirs of the California
Academy of Sciences, 5, pp. 1–38.
Merriam, J.C. 1908. Notes on the osteology of the thalattosaurian
genus Nectosaurus. University of California Publications, Bulletin
of the Department of Geology, 5: 217–223.
Müller, J. 2004. The relationships among diapsid reptiles and
the influence of taxon selection, In Recent advances in the
origin and early radiation of vertebrates. Edited by G. Arratia,
R. Cloutier and V.H. Wilson. Dr. Friedrich Pfeil, Munich,
Germany, pp. 379–408.
Müller, J. 2005. The anatomy of Askeptosaurus italicus from the
Middle Triassic of Monte San Giorgio and the interrelationships
of thalattosaurs (Reptilia, Diapsida). Canadian Journal of Earth
Sciences, 42(7): 1347–1367.
Müller, J., Renesto, S., and Evans, E.S. 2005. The marine diapsid
reptile Endennasaurus (Reptilia: Thalattosauriformes) from the
Late Triassic of Italy. Palaeontology, 48: 1–16.
Nicholls, E.L. 1999. A reexamination of Thalattosaurus and Necto-
saurus and the relationships of the Thalattosauria (Reptilia:
Diapsida). PaleoBios, 19: 1–29.
Nicholls, E. L., and Brinkman, D. 1993. New thalattosaurs (Reptilia:
Diapsida) from the Triassic Sulphur Mountain Formation of
Wapiti Lake, British Columbia. Journal of Paleontology, 67:
263–278.
Peyer, B. 1936a. Die Triasfauna der Tessiner Kalkalpen. X. Clarazia
schinzi nov. gen. nov. spec. Abhandlungen der schweizerischen
paläontologischen Gesellschaft, 57, pp. 1–61.
Peyer, B. 1936b. Die Triasfauna der Tessiner Kalkalpen. XI. He-
scheleria rübeli nov. gen. nov. spec. Abhandlungen der schwei-
zerischen paläontologischen Gesellschaft, 58, pp. 1–48.
Renesto, S. 1991. The anatomy and relationships of Endennasaurus
acutirostris (Reptilia, Neodiapsida) from the Norian (Late Triassic)
of Lombardy. Rivista Italiana di Paleontologia e Stratigrafia, 97:
409–430.
Rieppel, O. 1987. Clarazia and Hescheleria, a re-investigation of
two problematical reptiles from the Middle Triassic of Monte
San Giorgio, Switzerland. Palaeontographica A, 195: 101–129.
Rieppel, O. 1998. The systematic status of Hanosaurus hupehensis
(Reptilia, Sauropterygia) from the Triassic of China. Journal of
Vertebrate Paleontology, 18: 545–557.
Rieppel, O., Liu, J., and Bucher, H. 2000. The first record of a
thalattosaur reptile from the Late Triassic of southern China
(Guizhou Province, P.R. China). Journal of Vertebrate Paleontology,
20: 507–514.
Storrs, G.W. 1991. Note on a second occurrence of thalattosaur
remains (Reptilia: Neodiapsida) in British Columbia. Canadian
Journal of Earth Science, 28: 2065–2068.
Yin, G.-Z., Zhuo, X.-G., Cao, Z.-T., Yu, Y.-Y., and Luo, Y.M.
2000. A preliminary study on the early Late Triassic marine rep-
tiles from Guanling, Guizhou, China. Geology, Geochemistry,
28: 1–22.
