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Masiakasaurus-like theropod teeth from Brazil and other new papers



From: Ben Creisler
bcreisler@gmail.com

A few new papers:

Rafael Matos Lindoso, Manuel Alfredo Medeiros, Ismar de Souza Carvalho
& Thiago da Silva Marinho (2012)
Masiakasaurus-like theropod teeth from the Alcântara Formation, São
Luís Basin (Cenomanian), northeastern Brazil
Cretaceous Research (advance online publication)
http://dx.doi.org/10.1016/j.cretres.2012.03.002
http://www.sciencedirect.com/science/article/pii/S0195667112000407



The Alcântara Formation (Early Cenomanian, São Luís Basin) that crops
out on the northern shoreline of Maranhão State, northeastern Brazil,
presents a unique record of northern South American vertebrates that
is similar to North African Albian–Cenomanian records. In this paper,
nine theropod teeth are described. Some of these show a long, distally
curved profile, laterally compressed, with a textured distal surface
and a basal cross section from elliptical to subcircular. The mesial
carina is deflected lingually, the distal one is deflected labially
and both are gently serrated. This set of dental features is peculiar
to and typical of the Malagasy genus Masiakasaurus from the Late
Cretaceous (Maastrichtian). The Alcântara Formation material is here
referred to a noasaurid related to Masiakasaurus knopfleri in spite of
the spatial and temporal distance between them. This referral is based
on the similarity of the Brazilian material with the easily
distinguishable dental features of the Malagasy species. This new
record should be taken into account in interpretations of the
historical biogeography of noasaurids in Gondwana.


====

Romain Vullo, Eric Buffetaut, Didier Néraudeau, Jean Le Lœuff,
Jean-François Heil & Michèle Dunand (2012)
The “Megalosaur” (Dinosauria, Sauropoda) from Saint-Agnant
(Charente-Maritime, France): Description and stratigraphical origin.
Annales de Paléontologie (advance online publication)
http://dx.doi.org/10.1016/j.annpal.2012.02.002
http://www.sciencedirect.com/science/article/pii/S0753396912000043



The “Megalosaur” remains from Saint-Agnant (Charente-Maritime,
France), reported as early as 1881 by Boissellier, are here described
and figured for the first time. These bones, as well as a few
additional specimens from the nearby locality of Soubise, belong in
fact to an indeterminate sauropod. The stratigraphical position of
these remains unambiguously indicates an infra-Cenomanian age.
However, the presence in this area of continental deposits with
Purbeckian and Wealden facies does not allow to decide between an
earliest or late Early Cretaceous age.

====

Armando H. Escobedo-Galván & Constantino González-Salazar (2012)
Survival and extinction of sex-determining mechanisms in Cretaceous tetrapods.
Cretaceous Research (advance online publication)
http://dx.doi.org/10.1016/j.cretres.2012.02.016
http://www.sciencedirect.com/science/article/pii/S0195667112000377



Recognizing the mechanisms that influence the survival/extinction
rates of species as a result of environmental changes in the past may
help to understand future trends in biodiversity loss by current
global change. In this study we examined whether non-dinosaur
tetrapods with genetic sex determination (ZZ-ZW and XX-XY) and
temperature-dependent sex determination (TSD) led to differential
survival at the Cretaceous/Palaeogene boundary event. Our results
showed that 79% of the species with XY mechanism went extinct, while
13% and 23% of the species with TSD and ZW mechanisms went extinct,
respectively. Our results suggest that sex-determining mechanisms
might have played an important role in the survival of species. Other
possible variables should also be considered to determine the role of
plasticity of TSD and GSD species in mass extinction processes.