A new Upper Triassic cynodont-bearing fossiliferous site from southern Brazil, with taphonomic remarks and description of a new traversodontid taxon

The nasal cavity of two traversodontid cynodonts (Eucynodontia, Gomphodontia) from the Upper Triassic of Brazil

Journal of Paleontology ◽

10.1017/jpa.2021.6 ◽

2021 ◽

pp. 1-16

Author(s):

Arymathéia Santos Franco ◽

Rodrigo Temp Müller ◽

Agustín G. Martinelli ◽

Carolina A. Hoffmann ◽

Leonardo Kerber

Keyword(s):

Nasal Cavity ◽

Fossil Record ◽

Nasal Septum ◽

Internal Surface ◽

Nasolacrimal Duct ◽

Upper Triassic ◽

Late Triassic ◽

Southern Brazil ◽

Dorsal Region ◽

Left And Right

Abstract Traversodontidae is a group of Triassic herbivorous/omnivorous cynodonts that represents the most diversified lineage within Cynognathia. In southern Brazil, a rich fossil record of late Middle/mid-Late Triassic cynodonts has been documented, with Exaeretodon riograndensis Abdala, Barberena, and Dornelles, 2002 and Siriusgnathus niemeyerorum Pavanatto et al., 2018 representing two abundant and well-documented traversodontids. The present study provides a comparative analysis of the morphology of the nasal cavity, nasal recesses, nasolacrimal duct, and maxillary canals of both species using computed tomography, highlighting the changes that occurred in parallel to the origin of mammaliaforms. Our results show that there were no ossified turbinals or a cribriform plate delimiting the posterior end of the nasal cavity, suggesting these structures were probably cartilaginous as in nonmammaliaform cynodonts. Both species show lateral ridges on the internal surface of the roof of the nasal cavity, but the median ridge for the attachment of a nasal septum is absent. Exaeretodon riograndensis and S. niemeyerorum show recesses on the dorsal region of the nasal cavity, which increase the volume of the nasal cavity, potentially enhancing the olfactory chamber and contributing to the sense of smell. On the lateral sides of the nasal cavity, the analyzed taxa show a well-developed maxillary recess. Although E. riograndensis and S. niemeyerorum have roughly similar nasal cavities, in the former taxon, the space between the left and right dorsal recesses of the nasal cavity is uniform along its entire extension, whereas this space narrows posteriorly in S. niemeyerorum. Finally, the nasolacrimal duct of S. niemeyerorum is more inclined anteroposteriorly than in E. riograndensis.

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New Dinosauriform (Ornithodira, Dinosauromorpha) Record from the Upper Triassic of Southern Brazil

Paleontological Research ◽

10.2517/2014pr012 ◽

2014 ◽

Vol 18 (2) ◽

pp. 118-121 ◽

Cited By ~ 7

Author(s):

Rodrigo Temp Müller ◽

Max Cardoso Langer ◽

Alex Sandro Schiller Aires ◽

Sérgio Dias-da-silva

Keyword(s):

Upper Triassic ◽

Southern Brazil

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Lacertoid footprints from the Upper Triassic (Santa Maria Formation) of Southern Brazil

Palaeogeography Palaeoclimatology Palaeoecology ◽

10.1016/j.palaeo.2008.02.006 ◽

2008 ◽

Vol 262 (3-4) ◽

pp. 140-156 ◽

Cited By ~ 13

Author(s):

Rafael Costa da Silva ◽

Jorge Ferigolo ◽

Ismar de Souza Carvalho ◽

Antonio Carlos Sequeira Fernandes

Keyword(s):

Upper Triassic ◽

Southern Brazil ◽

Santa Maria

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A New Prozostrodontian Cynodont (Eucynodontia, Probainognathia) from the Upper Triassic of Southern Brazil

Journal of Vertebrate Paleontology ◽

10.1080/02724634.2020.1782415 ◽

2020 ◽

Vol 40 (3) ◽

pp. e1782415 ◽

Cited By ~ 1

Author(s):

Micheli Stefanello ◽

Leonardo Kerber ◽

Agustin G. Martinelli ◽

Sérgio Dias-Da-Silva

Keyword(s):

Upper Triassic ◽

Southern Brazil

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Trucidocynodon riograndensis gen. nov. et sp. nov. (Eucynodontia), a new cynodont from the Brazilian Upper Triassic (Santa Maria Formation)

Zootaxa ◽

10.11646/zootaxa.2382.1.1 ◽

2010 ◽

Vol 2382 (1) ◽

pp. 1 ◽

Cited By ~ 34

Author(s):

TÉO VEIGA DE OLIVEIRA ◽

MARINA BENTO SOARES ◽

CESAR LEANDRO SCHULTZ

Keyword(s):

Upper Triassic ◽

New Taxon ◽

Southern Brazil ◽

Morphological Gradient ◽

Caudal Vertebrae ◽

Secondary Palate ◽

Limb Posture ◽

Posterior Trunk ◽

Santa Maria

An almost complete skeleton of a new carnivorous cynodont from the Upper Triassic of Southern Brazil, Trucidocynodon riograndensis gen. nov. et sp. nov., is described. The new taxon is very similar to Ecteninion lunensis Martinez et al. 1996 from Upper Triassic of Argentina (Ischigualasto Formation). Both have an elongated skull, large pterygoid flanges, a well developed orbitosphenoid, a relatively short osseous secondary palate, greatly developed canines and sectorial postcanines with posteriorly directed cusps. However, the new taxon shows some differences relative to E. lunensis such as an open pterygoparoccipital foramen, the posterior opening of the post-temporal foramen enclosed by tabular and squamosal, and upper incisors with serrated cutting edges. The more remarkable features of the postcranium of T. riograndensis are the presence of 32 presacral vertebrae, a greater number than in most of non-mammaliaform cynodonts, the accentuated lumbarisation of the posterior trunk vertebrae and a remarkable morphological gradient in the caudal vertebrae; the femur and humerus show some interesting adaptations suggesting a more upright limb posture. The overall morphology of the astragalocalcaneal complex is similar to that of Diademodon and of the therocephalian Bauria.

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