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Exaeretodon (traversodontid synapsid) jaw from Triassic of Brazil



From: Ben Creisler
bcreisler@gmail.com

A new online paper:

Alexandre Liparini, Téo V. Oliveira, Flávio A. Pretto, Marina B.
Soares & Cesar L. Schultz (2013)
The lower jaw and dentition of the traversodontid Exaeretodon
riograndensis Abdala, Barberena & Dornelles, from the Brazilian
Triassic (Santa Maria 2 Sequence, Hyperodapedon Assemblage Zone).
Alcheringa (advance online publication)
DOI:10.1080/03115518.2013.752607
http://www.tandfonline.com/doi/full/10.1080/03115518.2013.752607


Exaeretodon riograndensis Abdala, Barberena, & Dornelles, 2002 is the
most abundant traversodontid preserved in the basal Santa Maria 2
Sequence (Hyperodapedon Assemblage Zone), southern Brazil and is
closely related to Exaeretodon argentinus Cabrera, 1943 from the
Ischigualasto Formation, Argentina. Previous anatomical studies of E.
riograndensis have focused mainly on cranial material and little is
known about the morphology of its lower dentition or postdentary
bones. We describe the first fairly complete postdentary series of the
mandible of E. riograndensis and provide additional information on its
lower dentition. The postdentary bones of E. riograndensis include a
complex coronoid, an angular with a delicate reflected lamina and a
stout retroarticular process of the articular, contrasting with the
morphology reconstructed for Argentinean specimens, which possess a
small retroarticular process. Apart from that, the postdentary bones
do not differ significantly from those known for E. argentinus, a fact
expected due to the great similarity between other skeletal features
of these species. Furthermore, the lower postcanines of E.
riograndensis have virtually the same structure as those of E.
argentinus, with an approximate quadrangular shape in occlusal view.
Moreover, the transverse cusp row is placed anteriorly and comprises a
lingual and a buccal cusp, and the occlusal basin delimited by the
four main cusps is relatively deep. The new material does not add any
taxonomically diagnostic features to E. riograndensis. However, the
fossils greatly improve our understanding of the anatomy of the
Brazilian species.