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Mosasaur and other new marine reptile refs



From: Ben Creisler
bh480@scn.org

Some new papers about marine reptiles:

Johan Lindgren, Michael J. Everhart, Michael W. Caldwell (2011)
Three-Dimensionally Preserved Integument Reveals Hydrodynamic Adaptations
in the Extinct Marine Lizard Ectenosaurus (Reptilia, Mosasauridae). 
PLoS ONE 6(11): e27343. 
doi:10.1371/journal.pone.0027343
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0027343

The physical properties of water and the environment it presents to its
inhabitants provide stringent constraints and selection pressures affecting
aquatic adaptation and evolution. Mosasaurs (a group of secondarily aquatic
reptiles that occupied a broad array of predatory niches in the Cretaceous
marine ecosystems about 98?65 million years ago) have traditionally been
considered as anguilliform locomotors capable only of generating short
bursts of speed during brief ambush pursuits. Here we report on an
exceptionally preserved, long-snouted mosasaur (Ectenosaurus clidastoides)
from the Santonian (Upper Cretaceous) part of the Smoky Hill Chalk Member
of the Niobrara Formation in western Kansas, USA, that contains
phosphatized remains of the integument displaying both depth and structure.
The small, ovoid neck and/or anterior trunk scales exhibit a longitudinal
central keel, and are obliquely arrayed into an alternating pattern where
neighboring scales overlap one another. Supportive sculpturing in the form
of two parallel, longitudinal ridges on the inner scale surface and a
complex system of multiple, superimposed layers of straight, cross-woven
helical fiber bundles in the underlying dermis, may have served to minimize
surface deformation and frictional drag during locomotion. Additional
parallel fiber bundles oriented at acute angles to the long axis of the
animal presumably provided stiffness in the lateral plane. These features
suggest that the anterior torso of Ectenosaurus was held somewhat rigid
during swimming, thereby limiting propulsive movements to the posterior
body and tail.

==

Rudolf Stockar and Silvio Renesto (2011)
Co-occurrence of Neusticosaurus edwardsii and N. peyeri (Reptilia) in the
Lower Meride Limestone (Middle Triassic, Monte San Giorgio).
Swiss Journal of Geosciences (advance online publication)
DOI: 10.1007/s00015-011-0077-x
http://www.springerlink.com/content/0r6h381u53896095/


A newly opened excavation in the Cassina beds of the Lower Meride Limestone
(Monte San Giorgio UNESCO World Heritage List, Canton Ticino, Switzerland),
has yielded a pachypleurosaurid (Reptilia: Sauropterygia) specimen which is
identified as Neusticosaurus peyeri. The resulting co-occurrence of N.
peyeri and N. edwardsii, the latter so far regarded as the sole species of
the genus present in this horizon, challenges the hypothesis of a single
anagenetic lineage in Neusticosaurus species from Monte San Giorgio. In
addition, it leads to a reconsideration of the phylogenetic inferences
about Neusticosaurus evolution in the Monte San Giorgio area. The
stratigraphic distribution of the Neusticosaurus species in the Monte San
Giorgio basin is updated on the basis of recent finds.
== 

Torsten M. Scheyer and Markus Moser (2011)
Survival of the thinnest: rediscovery of Bauer?s (1898) ichthyosaur tooth
sections from Upper Jurassic lithographic limestone quarries, south Germany.
Swiss Journal of Geosciences (advance online publication)
DOI: 10.1007/s00015-011-0076-y
http://www.springerlink.com/content/f22706g065m2w1r1/

The re-discovery of nine petrographic slides from the late 19th century at
the palaeontological collections of the University of Zurich, showing
thin-sectioned ichthyosaur teeth, revealed these slides be the only
preserved remains of the historical collection of Upper Jurassic
ichthyosaurs from the Bavarian State Collection for Palaeontology and
Geology; fossil material which, up to now, was thought to have been
completely destroyed during World War II. Here the history of these slides,
from their origin in Munich as part of the doctoral thesis of Franz Bauer
(1898) to their rediscovery in Zurich in 2010 is presented. Furthermore, a
complete overview of all slides is given to elucidate their scientific
value with the background of up-to-date knowledge of ichthyosaur dentition
and tooth histology, including aspects of tissue and growth mark
identification. As such, the sectioned teeth show an exposed layer of
acellular cementum at the tooth neck, and sets of short and long period
growth lines in the orthodentine. The slides of one tooth are part of the
original syntype material of Aegirosaurus leptospondylus (Wagner). They
reveal an oval rather than a rectangular shape of the root, as well as the
presence of peculiar vascular canals, interpreted as secondary osteodentine
deposition, in the peri-pulpal orthodentine. 

==




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