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More mosasaur papers in Bulletin de la Société Géologique de France



From: Ben Creisler
bcreisler@gmail.com


Another issue of the Bulletin de la Société Géologique de France is
out online with papers from the Mosasaurs, Third International
Congress – Part 2:


http://bsgf.geoscienceworld.org/content/183/2.toc


The first issue was mentioned back in April:

http://dml.cmnh.org/2012Apr/msg00019.html

====

Anusuya Chinsamy, Cemal Tunoǧlu, and Daniel B. Thomas (2012)
Dental microstructure and geochemistry of Mosasaurus hoffmanni
(Squamata: Mosasauridae) from the Late Cretaceous of Turkey.
Bulletin de la Société Géologique de France 183:85-92,
doi:10.2113/gssgfbull.183.2.85
http://bsgf.geoscienceworld.org/content/183/2/85.abstract


Mosasaurus hoffmanni from Devrekani, Turkey is among the geologically
youngest of the ancient aquatic predators. In addition, M. hoffmanni
is the only Mesozoic vertebrate reported from Turkey, and has proven
useful in the understanding of paleogeographic segregation within
Mosasauridae. Here we provide an analysis of the histology and
geochemistry of a functional maxillary tooth of this Turkish mosasaur.
Dental histology included descriptions of lines of von Ebner and
contour lines of Owen in dentine, as well as microstructural details
pertaining to the enamel structure. Considering the spacing of the
lines of von Ebner, the odontoblast deposition of the dentine (at the
level of sectioning of the crown) was estimated to have taken
approximately 511 days. A replacement tooth was fortuitously
discovered upon sectioning the functional tooth, and given the
thickness of the dentine visible, it is estimated that it took 233
days to deposit the centripetal layer of dentine. Energy dispersive
spectroscopy, x-ray diffractometry, fusion disc x-ray fluorescence and
Sr isotope measurements suggested that the tooth had undergone
heterogeneous diagenetic alteration. Despite signs of alteration, the
anatomy and chemistry of the M. hoffmanni teeth provided significant
paleobiological and paleo-environmental insight.

==

Marta S. Fernández and Zulma Gasparini (2012)
Campanian and Maastrichtian mosasaurs from Antarctic Peninsula and
Patagonia, Argentina.
Bulletin de la Société Géologique de France 183:93-102,
doi:10.2113/gssgfbull.183.2.93
http://bsgf.geoscienceworld.org/content/183/2/93.abstract



Mosasaurs from Antarctica have been recovered from the late Campanian
and early and late Maastrichtian in James Ross, Vega and Seymour
Islands within the James Ross basin. Tylosaurinae are represented by
the late Campanian-early Maastrichtian remains of Taniwhasaurus
antarcticus [Novas et al., 2002] and by late Maastrichtian
Tylosaurinae indet.; Plioplatecarpinae by late Maastrichtian
Plioplatecarpus sp.; and Mosasaurinae by late Maastrichtian “Liodon”
sp., Mosasaurus sp. and Mosasaurinae indet. Materials from Cape Lamb,
recently identified in the Museo de La Plata collection (Argentina),
suggest that the stratigraphic range of Plioplatecarpus and “Liodon”
within the James Ross basin extends back to the early Maastrichtian.
At present, the holotype of T. antarcticus is the most complete
specimen exhumed from Antarctica. In northern Patagonia, mosasaurs
have been recovered from the late Maastrichtian of the Jagüel
Formation, Neuquén basin. Patagonian mosasaurs are represented by
Mosasaurus sp. aff. M. hoffmanni, Plioplatecarpus sp., Prognathodon
sp., and Mosasaurinae indet. Presently, no Tylosaurinae have been
found in Patagonia. Both in the James Ross and Neuquén basins,
Mosasaurus sp. and Plioplatecarpus sp. occurred close to the K/Pg.
boundary.


==

María Eurídice Páramo-Fons.eca (2012)
Mosasauroids from Colombia
Bulletin de la Société Géologique de France 183:103-109,
doi:10.2113/gssgfbull.183.2.103
http://bsgf.geoscienceworld.org/content/183/2/103.abstract


An overview of the main traits of the mosasauroid remains found in
Colombia is presented. Three stratigraphic levels have been identified
as mosasauroid-bearing beds. In adition to the already known Turonian
material, new fossils found in Coniacian and Campanian rocks are
preliminary described. The taphonomic and geological features of the
findings, as well as the differences in age and anatomical morphology
of the new Colombian mosasauroid remains open new perspectives for the
analysis of processes of adaptation to marine life that occurred in
mosasaurs during the Cretaceous.


===

Eric Buffetaut and Nathalie Bardet (2012)
The mosasaurid (Squamata) Prognathodon in the Maastrichtian (Late
Cretaceous) of the Cotentin Peninsula (Normandy, northwestern France).
Bulletin de la Société Géologique de France 183:111-115,
doi:10.2113/gssgfbull.183.2.111
http://bsgf.geoscienceworld.org/content/183/2/111.abstract

Although the presence of mosasaurids in the Late Cretaceous
(Maastrichtian) Baculites limestone of the Cotentin peninsula, in the
western part of Normandy (France), was reported as early as 1873 by
Henri-Emile Sauvage, this occurrence has largely been overlooked by
subsequent authors. In this paper we review Sauvage’s original
material (an isolated tooth – the type of Mosasaurus platyodon) and
describe an additional, hitherto unpublished, tooth crown also from
the Baculites Limestone of the Cotentin and refer both to the
globidensine mosasaur Prognathodon. Mosasaurus platyodon Sauvage, 1873
is considered a nomen dubium.

===

Nathalie Bardet, Xabier Pereda Suberbiola, J.-Carmelo Corral, Juan
Ignacio Baceta, José Ángel Torres, Benjamín Botantz, and Gorka Martin
(2012)
A skull fragment of the mosasaurid Prognathodon cf. sectorius from the
Late Cretaceous of Navarre (Basque-Cantabrian Region)
Bulletin de la Société Géologique de France 183:117-121,
doi:10.2113/gssgfbull.183.2.117
http://bsgf.geoscienceworld.org/content/183/2/117.abstract


In recent years, the discovery of isolated teeth from the Late
Cretaceous (Campanian-Maastrichtian) of the Basque-Cantabrian Region,
in the north of the Iberian Peninsula, has permitted to recognise at
least four different mosasaurid taxa in several sites of Alava and
Condado de Treviño: Mosasaurus lemonnieri, Prognathodon solvayi,
Platecarpus cf. ictericus and Tylosaurus sp. A new specimen, which
consists of a fragment of skull with articulated portions of the
maxilla and prefrontal, from the Campanian of Navarre is described
here. This material is assigned to Prognathodon cf. sectorius on the
basis of dental features. It constitutes the only cranial remain and
the most significant mosasaurid fragment known to date in the Iberian
Peninula. P. sectorius was previously recorded from the Maastrichtian
of New-Jersey and The Netherlands.


==

Michael J. Polcyn, Johan Lindgren, Nathalie Bardet, Dirk Cornelissen,
Louis Verding, and Anne S. Schulp (2012)
Description of new specimens of Halisaurus arambourgi Bardet & Pereda
Suberbiola, 2005 and the relationships of Halisaurinae.
Bulletin de la Société Géologique de France 183:123-136
doi:10.2113/gssgfbull.183.2.123
http://bsgf.geoscienceworld.org/content/183/2/123.abstract

Halisaurine mosasaurs are poorly known, represented by a small number
of specimens from the Santonian-Maastrichtian (~86 Ma – ~66 Ma), but
enjoyed broad palaeobiogeographic distribution during that time. They
are important for understanding mosasaur evolution because certain
aspects of their morphology retain the relatively plesiomorphic or
minimally modified squamate conditions; however, existing material is
limited and certain anatomical details are lacking. We report here two
new specimens of Halisaurus arambourgi including a well-preserved,
nearly complete skull and postcranial skeleton, and a partial skull
that preserves details of the braincase and quadrate. We focus our
description on morphology that augments the original description of
this species and provides comparisons with other halisaurines.
Braincase and temporal arcade characters confirm the plesiomorphic
nature of Halisaurus, supporting a relatively basal position of
Halisaurinae within Mosasauridae. Comparisons of cranial morphology
support reconstruction of relationships within Halisaurinae,
indicating that H. arambourgi is most closely related to H.
platyspondylus, Phosphorosaurus (= H. ortliebi) is the sister taxon to
those taxa, and Eonatator is the most basal described halisaurine. The
proportions of the epipodials and the caudal vertebral centrum
morphometrics indicate H. arambourgi is more derived than the
Santonian to early Campanian Eonatator sternbergii but less derived
than a Halisaurus sp. specimen from the mid-Maastrichtian of the
Moreno Formation of California, USA. Moreover, vertebral morphometrics
reveals that H. arambourgi possessed a downturned tail that likely
supported a crescent-like fluke.

===

Michael J. Polcyn and James Lamb (2012)
The snout of Halisaurus platyspondylus : phylogenetic and functional
implications.
Bulletin de la Société Géologique de France 183:137-143
doi:10.2113/gssgfbull.183.2.137
http://bsgf.geoscienceworld.org/content/183/2/137.abstract


New material of Halisaurus platyspondylus allows description of the
snout elements for the first time. The specimen was recovered from the
Late Maastrichtian New Egypt Formation in Gloucester County, New
Jersey. Portions of the frontal, both prefrontals, and the left
quadrate are preserved and are nearly identical to the USNM H.
platyspondylus specimen. It can be excluded from H. arambourgi by the
extensive sutural contact of the prefrontal and ventral frontal. The
new material demonstrates development of a relatively broad short
skull in H. platyspondylus as in H. arambourgi, and articulations of
constituent elements reveal a strong, akinetic snout. This stands in
contrast to the elongate, narrow skulls of more basal halisaurines
such as Eonatator. This pattern, also seen in derived members of other
mosasaurid subfamilies, suggests a shift from high velocity jaw
closure for prey acquisition in more basal forms to robust skulls
optimized for increased bite force in some more derived forms.

===

William B. Gallagher, Kenneth G. Miller, Robert M. Sherrell, James V.
Browning, M. Paul Field, Richard K. Olsson, Peter J. Sugarman, Steven
Tuorto, and Hendra Wahyudi (2012)
On the last mosasaurs: Late Maastrichtian mosasaurs and the
Cretaceous-Paleogene boundary in New Jersey.
Bulletin de la Société Géologique de France 183:145-150
doi:10.2113/gssgfbull.183.2.145
http://bsgf.geoscienceworld.org/content/183/2/145.abstract


New data regarding the placement of the Cretaceous-Paleogene (K/Pg)
boundary in New Jersey is presented based on a recent campaign of
drill coring boundary sections in the Atlantic coastal plain of
southern New Jersey. The occurrence of late Maastrichtian mosasaurs
worldwide and in New Jersey is reviewed in light of the continuing
controversy over the rate and cause of the extinction at the K/Pg
boundary. At the Meirs Farm site in Monmouth County, NJ, the
biostratigraphic position of mosasaur specimens (Halisaurus
platyspondylus, Mosasaurus hoffmann) is related to the occurrence of
an iridium excursion of 0.5 ppb (5x background levels) in the basal
Hornerstown Formation just above the upper Maastrichtian New Egypt
Formation. Other specimens in museum collections obtained during the
acme of nineteenth century marl mining are from this area of the
Maastrichtian outcrop belt in New Jersey. It is concluded that late
Maastrichtian mosasaurs show no diminution of their biogeographic
ranges and are not particularly rare in New Jersey in comparison to
older mosasaur faunas. Mosasaurs became extinct in association with
the collapse of the marine food web at the K/Pg boundary, and were
replaced as apical marine predators in the early Danian by a variety
of crocodilians.

===

Amy Burnell, Sean Collins, and Bruce A. Young (2012)
Vertebral morphometrics in Varanus.
Bulletin de la Société Géologique de France 183:151-158
doi:10.2113/gssgfbull.183.2.151
http://bsgf.geoscienceworld.org/content/183/2/151.abstract

The forces acting on the vertebral column of varanid lizards differ
greatly during swimming and walking. To examine the long-term impact
of these forces, the dorsal vertebrae of terrestrial and aquatic
species of Varanus were compared using 3-D laser scanning and
morphometric analysis. There were significant differences between the
two groups in vertebral anatomical features, particularly in the
articular surfaces. Further analysis demonstrated that the dorsal
vertebrae could be significantly divided into three groups of nearly
equal size: the sternal group (dorsal vertebrae 1–7), the middle group
(dorsal vertebrae 8–14), and the pelvic group (dorsal vertebrae
15–22). Within each of these groups there was significant differences
between the terrestrial and aquatic species; these differences were
least in the more conserved sternal region and greatest in the highly
variable pelvic region. The results suggest that vertebral
morphometrics can be used as a tool to further delineate the habitat
preferences of extinct varanoid lizards, and could serve to highlight
the functional transitions between terrestrial and aquatic species.

===

Amy Burnell, Sean Collins, and Bruce A. Young (2012)
The postpulmonary septum of Varanus salvator and its implication for
Mosasaurian ventilation and physiology.
Bulletin de la Société Géologique de France 183:159-169
doi:10.2113/gssgfbull.183.2.159
http://bsgf.geoscienceworld.org/content/183/2/159.abstract


The postpulmonary septum (PPS) is a relatively thick sheet of
connective tissue covering the inferior surface of the lungs in
varanid lizards. The primary connection of the PPS is to the medial
surface of the ribs; additional connections occur to the inferior
midline of the dorsal vertebrae, the pericardium, and a direct
(through loose connective tissue) link to the surface of the lung. The
PPS effectively partitions the coelomic cavity into peritoneal and
pleural cavities. Investigation demonstrates that the PPS is not
capable of preventing displacement of the more caudal (peritoneal)
viscera, which is displaced cranially during terrestrial locomotion;
this cranial displacement could impinge on the tidal volume of the
lungs. Kinematic analyses of terrestrial and aquatic locomotion in
Varanus salvator document the different propulsive mechanics used
during movement through these two media, and, most importantly, the
marked reduction in lateral displacement of the trunk during swimming.
These findings, when combined with previous studies of the
cardiovascular and respiratory system of varanids performing
terrestrial locomotion, suggest that mosasaurs had a versatile,
effective respiratory system and were likely capable of both sustained
swimming and prolonged submersion, such as during ambush foraging.