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Clevosaurus (Rhynchocephalia) dental morphology, from Upper Triassic of Brazil



Ben Creisler
bcreisler@gmail.com

New in PLoS ONE:

Paula Rosario Romo de Vivar Martínez  & Marina Bento Soares (2015).
Dentary Morphological Variation in Clevosaurus brasiliensis
(Rhynchocephalia, Clevosauridae) from the Upper Triassic of Rio Grande
do Sul, Brazil.
PLoS ONE 10(3): e0119307
doi:10.1371/journal.pone.0119307
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0119307


Clevosaurus was a cosmopolitan rhynchocephalian genus, known from the
Late Triassic to the Early Jurassic. In South America this genus is
represented by C. brasiliensis, an important component of the Linha
São Luiz taphocoenosis, on the top of the Norian Santa Maria 2
Sequence of Southern Brazil. The best preserved and most abundant bone
elements of C. brasiliensis are dentaries, in which variations of
shape and size are observed. The aim of this study is to describe and
evaluate the variation, using geometric morphometrics methods.
Geometric morphometric analysis of 10 specimens highlights variations
in relative size of the dentary. Most of the variation observed for
PC1 (83.3%) is likely related to ontogeny, and PC2 (10.0%) is likely
related to taphonomic signatures. The development patterns observed,
such as the growth of the dentary, consists of differential growth in
length between the posterior portion of the dentary, that grows at a
higher rate, regarding the anterior portion of the element. This
allometric growth is similar to what is observed in other
rhynchocephalians and is accompanied by the allometric skull growth,
similar to the trend exhibited by clevosaurs. The taphocoenosis is
bimodal (juveniles and adults) with a bias towards adult preservation.
Some diagenetic influence is reflected in deformed skulls and this is
observed in the tangent-plot. Finally, a strong correlation was
detected between the taphonomic signatures and the PC2, regarding
specially disarticulation and degree of fragmentation.


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