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Mesozoic marine reptiles, crocs, and turtles news and refs



From: Ben Creisler
bh480@scn.org

Some recent news stories and refs about non-dinosaurian reptiles during the
Mesozoic:

Marine Reptiles

Giant pliosaur skull
I posted an earlier link to a BBC news story about the pliosaur skull from
Dorset. This item at least addresses the "hype" factor in the media over
"biggest ever" claims:
http://news.nationalgeographic.com/news/2011/07/pictures/110712-pliosaur-fos
sil-sea-monster-biggest-skull/

Alaska Triassic thalattosaur
http://www.capitalcityweekly.com/stories/071311/new_856641234.shtml

New Zealand ichthyosaur
http://www.stuff.co.nz/science/5261815/Ancient-sea-monster-resurfaces-after-
100m-years

Terminonaris from Texas

News story with video:
http://www.physorg.com/news/2011-07-texas-native-million-year-old-croc.html

Ref (from May issue of JVP):
Thomas L. Adams, Michael J. Polcyn, Octávio Mateus, Dale A. Winkler & Louis
L. Jacobs (2011)
First occurrence of the long-snouted crocodyliform Terminonaris
(Pholidosauridae) from the Woodbine Formation (Cenomanian) of Texas
Journal of Vertebrate Paleontology 31(3):712-716 
DOI:10.1080/02724634.2011.572938
http://www.tandfonline.com/doi/abs/10.1080/02724634.2011.572938

==
Turtles

Jérémy Anquetin (2011)
Evolution and palaeoecology of early turtles: a review based on recent
discoveries in the Middle Jurassic.
Bulletin de la Société Géologique de France 182(3): 231-240 
DOI: 10.2113/gssgfbull.182.3.231
http://bsgf.geoscienceworld.org/cgi/content/abstract/182/3/231

In recent years, no less than five new species of early turtles have been
described worldwide. Among them are three new turtles from Middle Jurassic
deposits that partially fill a previous temporal and morphological gap in
our knowledge of the early evolution of these shelled amniotes:
Heckerochelys romani, Condorchelys antiqua and Eileanchelys waldmani. For
the first time, the phylogenetic position of these three new species is
tested in the context of the two presently competing cladistic models of
turtle evolution. The addition of these taxa to each matrix does not favour
or alter any of the two opposed hypotheses. However, it is demonstrated
here that, by documenting yet unknown stages in the evolution of several
morphological structures, these three species give stronger support to the
model of an extended phylogenetic stem for turtles. These new lines of
evidence include the structure of the vomer, the position of the aditus
canalis stapedio-temporalis and of the posterior opening of the canalis
cavernosus, and the morphology of the processus interfenestralis of the
opisthotic. 

Recent discoveries also reinvigorate the debate about the palaeoecology of
early turtles. Whereas simple morphological characters (e.g., shell
fontanelle, ligamentous bridge, flattened carapace) can be misleading,
forelimb proportions and shell bone histology have led to the conclusion
that most stem turtles (i.e., Proganochelys quenstedti, Palaeochersis
talampayensis, Proterochersis robusta, Kayentachelys aprix and meiolaniids)
were terrestrial forms. At least two out of the five recently described
early turtles have been convincingly interpreted as having aquatic habits:
Odontochelys semitestacea and Eileanchelys waldmani. More investigation is
needed, but this will undoubtedly trigger further debate on the primitive
ecology of turtles and on the origin of aquatic habits in testudines (i.e.,
the crown-group), respectively. 


Tyler R. Lyson, Walter G. Joyce, Georgia E. Knauss & Dean A. Pearson (2011)
Boremys (Testudines, Baenidae) from the latest Cretaceous and early
Paleocene of North Dakota: an 11-million-year range extension and an
additional K/T survivor.
Journal of Vertebrate Paleontology 31(4):729-737
DOI:10.1080/02724634.2011.576731
http://www.tandfonline.com/doi/abs/10.1080/02724634.2011.576731
(NOTE: pdf is now free!)

For over a century, the baenid turtle Boremys has been recognized as being
restricted to the Campanian of North America. Herein we describe new
material of Boremys sp. from the Hell Creek Formation (Maastrichtian) and
Fort Union Formation (Puercan) of southwestern North Dakota and eastern
Montana, increasing the stratigraphic range of this taxon by 11 million
years. The material was recovered from the base of the Hell Creek Formation
to 14 m above the pollen-calibrated K/T boundary in the basal Fort Union
Formation. Most of the specimens consist of isolated shell elements, which
are easily misidentified as belonging to a kinosternid or chelydrid turtle,
but complete shells are present as well. The presence of Boremys sp. in the
Hell Creek formation increases the baenid taxonomic diversity of this
particular rock unit to nine and the overall turtle diversity to 20 taxa,
and the presence of Boremys sp. in the Fort Union Formation increases the
number of baenid lineages that survive the K/T extinction event to eight.


Tyler R. Lyson and Walter G. Joyce (2011)
Cranial Anatomy and Phylogenetic Placement of the Enigmatic Turtle
Compsemys victa Leidy, 1856.
Journal of Paleontology 85(4):789-801. 2011 
doi: 10.1666/10-081.1 
http://www.bioone.org/doi/abs/10.1666/10-081.1
 
The skull of the enigmatic turtle Compsemys victa Leidy, 1856 is described.
A number of unique characteristics are apparent, including the extremely
thick nature of all cranial bones, the presence of rod-like epipterygoids,
placement of the foramen posterius canalis carotici interni halfway along
the contact between the pterygoid and basisphenoid, lack of cheek
emarginations, and the reduction of the size of the cavum tympani relative
to the orbit. Two differing global turtle analyses and one paracryptodiran
analysis were performed to determine the phylogenetic placement of C.
victa. Both global analyses converged by placing C. victa within
Paracryptodira, herein defined as the most inclusive clade that includes
Pleurosternon bullockii and Baena arenosa, but no species of living turtle,
whereas the paracryptodiran analysis places C. victa outside of Baenoidea,
herein defined as the least inclusive clade that contains P. bullockii and
B. arenosa. Although a number of similarities are apparent between C. victa
and the uncommon, extant testudinoid Platysternon megacephalum, the
available data indicate that these similarities are convergent, likely due
to their carnivorous diet. Taphonomic evidence reveals that basal
paracryptodires, including C. victa, preferred slow moving or ponded water
environments. The riverine habitat preference of baenodds must therefore be
derived.


Marcelo S. de la Fuente, Aldo M. Umazano, Juliana Sterli and José L.
Carballido (2011)
New chelid turtles of the lower section of the Cerro Barcino formation
(Aptian-Albian?), Patagonia, Argentina. 
Cretaceous Research 32(4): 527-537 
doi:10.1016/j.cretres.2011.03.007 
http://www.sciencedirect.com/science/article/pii/S0195667111000395

A new chelid species (Prochelidella cerrobarcinae nov. sp.) are described
from the Aptian-Albian? Puesto La Paloma Member, Cerro Barcino Formation,
northern of Chubut Province, Argentina. The basal section of this member,
which bears the turtle remains, is composed of tuffaceous mudstones with
plane parallel lamination, asymmetrical ripples and a chert intercalation
suggesting sub-aqueous deposition in a relatively shallow lacustrine
environment. Pr. cerrobarcinae nov. sp. is represented by post-cranial
remains of several specimens that not only represents the oldest
pleurodiran chelid record in the world but, together with the chelid
remains of Albian Lightning Ridge, New South Wales, Australia, indicates
that chelid diversification began well before the final fragmentation of
southern Gondwana.

Ling Wang, Xuming Zhou, Liuwang Nie, Xingquan Xia, Luo Liu, Yuan Jiang,
Zhengfeng Huang and Wanxin Jing (2011)
The complete mitochondrial genome sequences of Chelodina rugosa and Chelus
fimbriata (Pleurodira: Chelidae): implications of a common absence of
initiation sites (OL) in pleurodiran turtles. 
Molecular Biology Reports (advance online publication)
DOI: 10.1007/s11033-011-0957-1
http://www.springerlink.com/content/q086t82128u431n5/

Within the order Testudines, while phylogenetic analyses have been
performed on the suborder Cryptodira with complete mitochondrial genomes
(mitogenomes), mitogenomic information from another important suborder
Pleurodira has been inadequate. In the present study, complete
mitochondrial DNA (mtDNA) sequences of two chelid turtles Chelodina rugosa
and Chelus fimbriata were firstly determined, the lengths of which were
16,582 and 16,661 bp respectively. As the typical vertebrate mitogenome,
both mtDNAs consist of 13 protein coding genes, 2 ribosomal RNAs (rRNAs),
22 transfer RNAs (tRNAs), and a long noncoding region (control region, CR).
However, the initiation sites for light-strand replication (OL), which has
been identified in all reported Cryptodire mitogenomes, were not found in
the putative position of the two chelid turtles and African helmeted turtle
Pelomedusa subrufa. The results suggested that the absence of mitogenomic
initiation sites (OL) could be a characteristic of Pleurodira. Phylogenetic
relationships of chelid turtles and other turtles were reconstructed using
the reported mitogenomes. Both maximum likelihood (ML) and Bayesian
inference (BI) analyses suggested the monophyly of Pleurodira and
Cryptodira as well as a sister group relationship between the two chelid
turtles with strong statistical support. This phylogenetic framework was
also utilized to estimate divergence dates among lineages using
relaxed-clock methods combined with fossil evidence. Divergence estimates
revealed that genus Chelodina diverged from genus Chelus in Late Cretaceous
(~83 million years ago (mya)), and the time is consistent with the
vicariance of the fragments which was caused by Gondwana split. 



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