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Westphaliasaurus abstract and other recent Mesozoic marine reptile stuff



From: Ben Creisler
bh480@scn.org

Here is a translation of the abstract for the new paper on
Westphaliasaurus. A special thanks to co-author Leonie Schwermann for
providing an English translation of the abstract (with a few edits by me).
Also, a number of other papers about Mesozoic marine reptiles that have
been published or appeared online in the past few months.

Leonie Schwermann & Martin Sander (2011)
Osteologie und Phylogenie von Westphaliasaurus simonsensii: Ein neuer
Plesiosauride (Sauropterygia) aus dem Unteren Jura (Pliensbachium) von
Sommersell (Kreis Höxter), Nordrhein-Westfalen, Deutschland.[Osteology and
Phylogeny of Westphaliasaurus simonsensii, a new plesiosaurid
(Sauropterygia) from the Lower Jurassic (Pliensbachian) of Sommersell
(Kreis Höxter), North Rhine-Westphalia, Germany.] 
Geologie und Paläontologie in Westfalen (March 2011) 79: 56 pgs 
ISBN 978-3-940726-14-8

Abstract (translation)
In June 2007 the partially articulated skeleton of a plesiosaur from the
Lower Jurassic (Pliensbachian) was found in a clay pit named "Lücking" in
Sommersell, district Höxter, North Rhine-Westphalia, Germany. It was
recovered and afterwards prepared by the Museum of Natural History in
Münster (Westphalia). The stratigraphical position of the specimen is
between common taxa from the Hettangian and Sinemurian of Enland, and the
Toarcian of Southern Germany and England. 

The skull, as well as the distal parts of the limbs, is not preserved, but
the larger part of the axial skeleton is in place. A total of 76 vertebrae,
pectoral and pelvic girdles, and the proximal parts of the fore- and
hindlimbs (humerus, radius, ulna / femur, tibia, fibula) are present.
Carpals, tarsals and phalanges are scattered around the specimen. In
addition to the osteological description of the specimen, a comparison with
common Lower Jurassic taxa in the literature and with material from the
collections of the Natural History Museum in London and the "Staatliches
Museum für Naturkunde" in Stuttgart was made. Some characters clearly
distinguish the Sommersell taxon from established taxa. 

After the osteological comparison, the distinct taxonomic status of the
specimen was verified by a phylogenetic analysis. For this purpose, the
specimen was analyzed using the data matrix of Ketchum & Benson (2010). The
results supported conclusions made during the osteological description and
comparison, and show clearly that the specimen from Sommersell is a new
taxon. It is established based on the combination of a total of six
unambiguous synaptomorphies. Three of these synapomorphies are unique to
the Plesiosauridae. Together with Plesiosaurus dolichodeirus, Seeleyosaurus
guilelmiimperatoris, Microcleidus homalospondylus, Occitanosaurus
tournemirensis and Hydrorion brachypterygius the Sommersell taxon is
situated in the monophyletic taxon Plesiosauridae. The stratigraphical
position, as well as the paleogeographical position, also supports these
results. On the basis of the results of the phylogenetic analysis a new
genus and a new species, Westphaliasaurus simonsensii, are erected for the
taxon from Sommersell. 

Other new taxa:

Jun Liu; Olivier Rieppel; Da-Yong Jiang; Jonathan C. Aitchison; Ryosuke
Motani; Qi-Yue Zhang; Chang-Yong Zhou; Yuan-Yuan Sun (2011)
A new pachypleurosaur (Reptilia: Sauropterygia) from the lower Middle
Triassic of southwestern China and the phylogenetic relationships of
Chinese pachypleurosaurs  
Journal of Vertebrate Paleontology 31(2): 292-302 
DOI: 10.1080/02724634.2011.550363 
http://www.informaworld.com/smpp/content~db=all~content=a935221173~frm=title
link

A new genus and species of Pachypleurosauria, Dianopachysaurus dingi, gen.
et sp. nov., from a recently discovered Middle Triassic Lagersttte in the
Anisian Guanling Formation of Yunnan Province is described. The monophyly
of Pachypleurosauria, including all potential Chinese pachypleurosaurs in
this study, is supported by the rigorous cladistic analysis conducted here.
Phylogenetic relationships of Chinese pachypleurosaurs are clarified.
Wumengosaurus occupies the most basal position within Pachypleurosauria.
Keichousaurus and Dianopachysaurus form the monophyletic Keichousauridae
that is the sister group of all European pachypleurosaurs. Our cladistic
analysis also supports a previously proposed paleobiogeographic hypothesis
of an eastern Tethyan origin of pachypleurosaurs and their migration into
the western Tethyan faunal province. The existence of a long ghost lineage
as required by the paleobiogeographic hypothesis is greatly shortened by
the discovery of Dianopachysaurus. 

Chun Li; Olivier Rieppel; Xiao-Chun Wu; Li-Jun Zhao; Li-Ting Wang (2011)
A new Triassic marine reptile from southwestern China.  
Journal of Vertebrate Paleontology 31(2): 303-312 
DOI: 10.1080/02724634.2011.550368 
http://www.informaworld.com/smpp/content~db=all~content=a935220992~frm=title
link

A new genus and species of marine reptile is described from the Pelsonian
(Anisian, Middle Triassic) of Luoping County, Yunnan Province, southwestern
China. This diapsid reptile with a secondarily closed upper temporal fossa
is the sister taxon to Saurosphargis from the lower Muschelkalk (Anisian,
Middle Triassic) of central Europe. It further emphasizes the close faunal
affinities between the Eastern and Western Tethyan realm. The new taxon is
convergent on cyamodontoid placodonts in having developed a dorsal body
armor composed of small osteoderms. The underlying ribs are transversely
broadened so as to establish contact along their length, thus forming a
closed dorsal 'rib basket,' a unique morphology shared with Saurosphargis. 


Plesiosaurs:

F. Robin O'Keefe; Hallie P. Street; Benjamin C. Wilhelm; Courtney D.
Richards; Helen Zhu (2011) 
A new skeleton of the cryptoclidid plesiosaur Tatenectes laramiensis
reveals a novel body shape among plesiosaurs. 
Journal of Vertebrate Paleontology 31 (2): 330-339 
DOI: 10.1080/02724634.2011.550365 
http://www.informaworld.com/smpp/content~db=all~content=a935220144~frm=title
link

Current knowledge of plesiosaurs of clade Cryptoclidia is constrained by a
lack of fossils from outside the Oxford Clay deposits of England. Recent
fieldwork in the Sundance Formation of the Bighorn Basin, Wyoming, has
resulted in the recovery of significant new fossils of cryptoclidid
plesiosaurs, including the small-bodied form Tatenectes laramiensis. A new
partial skeleton of this taxon is reported here; it is the most complete
and best-preserved example of the taxon found to date, comprising a
complete dorsal vertebral series, many ribs and gastralia, and a complete
pelvic girdle. This skeleton illuminates several unique features of the
taxon, including a novel pattern of midline pachyostosis in the gastralia.
In addition, a range of both axial and appendicular morphological features
reveals that Tatenectes had a body shape unique among known plesiosaurs,
characterized by extreme dorsoventral compression, and modest
anteroposterior reduction. The combination of the new skeleton with
information from previous finds allows the first reconstruction of the
taxon. Tatenectes had a dorsoventrally compressed, oblate spheroid body
shape, with a high skeletal mass concentration in the ventral elements. We
hypothesize that these features were adaptations for increased near-surface
stability, perhaps allowing access to above normal wave base, inshore
environments in the shallow Sundance Seaway. 

Peggy Vincent (2011)
A re-examination of Hauffiosaurus zanoni, a pliosauroid from the Toarcian
(Early Jurassic) of Germany 
Journal of Vertebrate Paleontology 31(2): 340-351 
DOI: 10.1080/02724634.2011.550352 
http://www.informaworld.com/smpp/content~db=all~content=a935221391~frm=title
link


The holotype and only known specimen of the pliosauroid plesiosaur
Hauffiosaurus zanoni O'Keefe is a substantially complete and almost
entirely articulated skeleton from the Toarcian Posidonien-Schiefer (Upper
Lias, Lower Jurassic) of Holzmaden (Baden-Wrttemberg), Germany. The
original description of this specimen was preliminary, and this paper
presents a detailed re-description and revised diagnosis of the specimen,
thus adding significant, new anatomical information. Characters such as the
presence of a lateral palatal fenestra and the absence of a contact between
the internal nares and the palatines are examples of phylogenetically
relevant characters. The specimen presents a novel and unique combination
of characters and body proportions, including a long ilium, short ischia,
and propodials longer than any of their associated girdle bones, that
separate it from all other pliosauroid taxa. Its elongate snout and long,
slender teeth imply that this species most likely had a prey preference of
fish. 


Tamaki Sato; Xiao-Chun Wu; Alex Tirabasso; Paul Bloskie (2011)
Braincase of a polycotylid plesiosaur (Reptilia: Sauropterygia) from the
Upper Cretaceous of Manitoba, Canada. 
Journal of Vertebrate Paleontology 31(2): 313-329 
Authors: Tamaki Satoab; Xiao-Chun Wub; Alex Tirabassob; Paul Bloskieb 
DOI: 10.1080/02724634.2011.550358 
http://www.informaworld.com/smpp/content~db=all~content=a935219990~frm=title
link

The braincase of a polycotylid plesiosaur referable to Dolichorhynchops
from the Niobrara Formation (Santonian to the earliest Campanian) in
Manitoba, Canada, is described. The well-preserved material without matrix
permits observation of various anatomical features of the polycotylid
braincase with unprecedented clarity. A virtual reconstruction of the
braincase was created by using a three-dimensional scanning technique that
produces accurate reconstruction of missing or damaged elements and
demonstrates the three-dimensional relationships among the elements.
Comparison with other plesiosaurian braincases revealed previously
unrecognized characters and character states. The I-beam-shaped
parasphenoid, the relatively short pituitary fossa, and the anterior
process of the prootic are possible synapomorphies of the Polycotylidae or
of its subclades. It could be a challenge to confirm the presence of the
supraoccipital process and its median ridge, as well as the presence of the
fenestra ovalis, in polycotylid skulls because of the location and
orientation of these structures. Variable morphology of
basioccipital-basisphenoid contact and the paroccipital process in
Dolichorhynchops and related taxa require further investigation. The I-beam
of the parasphenoid and the wide contact surfaces of the basioccipital and
neighboring elements provide more resistance to flexion of the braincase.
Distribution of the extensive pterygoid-basicranium contact, the shape of
foramen magnum, anterior process of the prootic, and the short pituitary
fossa do not confirm the current phylogenetic hypotheses. The location and
orientation of the fenestra ovalis suggest the lack of a tympanic ear in
this plesiosaur. 

Benjamin P. Kear & Paul M. Barrett (2011)
Reassessment of the Lower Cretaceous (Barremian) pliosauroid Leptocleidus
superstes Andrews, 1922 and other plesiosaur remains from the nonmarine
Wealden succession of southern England.
Zoological Journal of the Linnean Society 161(3): 663?691
DOI: 10.1111/j.1096-3642.2010.00648.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2010.00648.x/abstract

The Lower Cretaceous (upper Berriasian to lowermost Aptian) nonmarine
Wealden succession of southern England has been a prolific source of
vertebrate fossils for over 180 years. The sequence is most famous for
terrestrial reptiles, particularly dinosaurs; however, significant aquatic
tetrapod discoveries including rare nonmarine plesiosaurs have also been
reported. The record of Wealden plesiosaurs currently incorporates a single
valid taxon, Leptocleidus superstes Andrews, 1922a, based on a partial
skeleton and skull from the Barremian Upper Weald Clay Formation of
Berwick, Sussex. Traditional classifications place this plesiomorphic
pliosauroid with basal Jurassic rhomaleosaurids; however, the genus
Leptocleidus has since become a ?waste basket? for various Cretaceous
rhomaleosaurid-like plesiosaurs from around the globe. In an attempt to
clarify this situation, the type specimen of L. superstes was reexamined
and redescribed. Previously unrecorded anatomical features were identified
including an elongate, gracile paraoccipital process on the
exoccipital-opisthotic, and tooth ornament comprising widely spaced, coarse
striations that are restricted to the lingual surface of the crown
(mesiodistal ?carinae? are absent). Other indeterminate pliosauroid remains
(recovered along with coeval elasmosaurids) from the upper
Berriasian?Valanginian Hastings Beds Group also exhibit potentially
diagnostic traits: an atlas centrum with no anterolateral exposure and with
ventral margin formed by the intercentrum; a single-headed rib articulation
on the atlas centrum extending onto the axis centrum; and epipodials that
are longer than broad. The placement of L. superstes is controversial in
recent phylogenies. To test the competing hypotheses, L. superstes together
with all closely related species were rescored into the most comprehensive
published phylogenetic data sets of Plesiosauria and Pliosauroidea.
Separate maximum parsimony and Bayesian analyses of each matrix unanimously
supported a relationship between L. superstes and pliosauroids but could
not confirm placement within either Rhomaleosauridae sensu stricto, or a
discrete ?leptocleidoid? clade. Examination of character states advocating
affinities amongst Leptocleidus spp. suggests homoplasy rather than clear
homology between what are potentially palaeobiogeographically disparate
genus-level taxa.


Ichthyosaurs:

Fischer, Valentin (2011)
New data on the ichthyosaur Platypterygius hercynicus and its implications
for the validity of the genus.
Acta Palaeontologica Polonica in press
available online 11 Apr 2011 
doi:10.4202/app.2011.0007
http://app.pan.pl/article/item/app20110007.html

The description of a nearly complete skull from the late Albian of
northwestern France reveals previously unknown anatomical features of
Platypterygius hercynicus (Kuhn 1946), and of European Cretaceous
ichthyosaurs in general. These include a wide frontal forming the
anteromedial border of the supratemporal fenestra, a parietal excluded from
the parietal foramen, and the likely presence of a squamosal, inferred from
a very large and deep facet on the quadratojugal. The absence of a
squamosal has been considered as an autapomorphy of the genus
Platypterygius for more than ten years and has been applied to all known
species by default, but the described specimen casts doubt on this putative
autapomorphy. Actually, it is shown that all characters that have been
proposed previously as autapomorphic for the genus Platypterygius are
either not found in all the species currently referred to this genus, or
are also present in other Ophthalmosauridae. Consequently, the genus
Platypterygius must be completely revised.

Christian Kolb, , Marcelo R. Sánchez-Villagra,  and Torsten M. Scheyer
(2011)
The palaeohistology of the basal ichthyosaur Mixosaurus Baur, 1887
(Ichthyopterygia, Mixosauridae) from the Middle Triassic: Palaeobiological
implications. 
Comptes Rendus Palevol (advance online publication)
doi:10.1016/j.crpv.2010.10.008 | 

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6X1G-51WV6TJ-1&_us
er=10&_coverDate=01%2F08%2F2011&_alid=1738079835&_rdoc=1&_fmt=high&_orig=sea
rch&_origin=search&_zone=rslt_list_item&_cdi=7242&_sort=r&_st=13&_docanchor=
&view=c&_ct=18&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5346
7fc7b21cb46c2aef20ad5e7cacee&searchtype=a

Here, we provide the first bone histological examination of an ontogenetic
series of the basal ichthyosaur Mixosaurus encompassing postnatal to large
adult specimens. Growth marks are present in sampled humeri, a femur, a
fibula, as well as in other skeletal elements (gastral ribs). Ontogenetic
changes are traceable throughout stylo- and zeugopodial development, but
interior remodelling and resorption deleted part of the internal growth
record in the primary cortex. Mixosaurus humeri started as flat structures
consisting of a core of endochondral woven bone and residual calcified
cartilage, whereas growth continued by deposition of periosteal
fibrolamellar and parallel-fibred bone. Unlike the fast-growing
post-Triassic ichthyosaurs that lack growth marks, microstructural and life
history data are now becoming available for a basal ichthyosaur. The high
growth rate of Mixosaurus may indicate that higher metabolic rates
characterised small, non-thunniform ichthyosaurs, as had been suggested
already for post-Triassic, cruising forms.

Maria Zammita (2010)
A review of Australasian ichthyosaurs. 
Alcheringa: An Australasian Journal of Palaeontology 34 (3): 281-292 
DOI: 10.1080/03115511003663939 
http://www.informaworld.com/smpp/content~db=all~content=a922668199~frm=title
link?words=ichthyosaur&hash=850180541


Ichthyosaur fossils have been recorded from four landmasses in the
Australasian region?Australia, New Zealand, New Caledonia and Timor?and
occur in all three systems of the Mesozoic. Most of the remains are
non-diagnostic, but at least three genera have been identified: Mixosaurus,
from the Middle Triassic of Timor; Shonisaurus, from the Upper Triassic of
New Caledonia; and Platypterygius, from the Lower Cretaceous of Australia
and New Zealand. Of these, Platypterygius contains the only material that
can be diagnosed to species level. However, current taxonomy of the
specimens is controversial, with two synonyms, P. australis and P.
longmani, persisting in the literature. An examination of cranial traits in
the 'quasi-holotype' of P. australis vs P. longmani demonstrates that they
represent the same taxon. Thus, P. longmani should be regarded as the
junior synonym. A neotype is also here designated for P. australis to
replace the original, which is presumed lost. 






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