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

Abstract

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.

The postcranial anatomy of Brasilodon quadrangularis and the acquisition of mammaliaform traits among non-mammaliaform cynodonts

“…The centra are flat on the anterior side and concave on the posterior side (platycoelous), as seen in some tritylodontids such as Tritylodon and Bienotheroides [19] and in the early mammaliaform Morganucodon [32]. Centra are deeply amphicoelous in most non-mammaliaform cynodonts (e.g., [12, 17–18, 38, 79–80]). The neural arches are poorly preserved, almost all vertebral processes are broken.…”

“…Costal plates are represented in all basal epicynodonts in which the postcranium is known [13, 84] and most cynognathians (e.g., Cynognathus , Diademodon , Luangwa , Andescynodon , Menadon , Protuberum , Pascualgnathus , and Scalenodon ; [17, 38, 80, 82]). They were lost in several traversodontids (e.g., Exaeretodon , Boreogomphodon ; [80, 85]) and all probainognathians (e.g., [18, 43, 83]).…”

The femoral anatomy of Pampadromaeus barberenai based on a new specimen from the Upper Triassic of Brazil

“…This Argentinean unit was recently radioisotopically dated as 231.4^0.3 Ma (Martínez et al 2011). Besides these two genera, the vertebrate fauna of the 'Janner' outcrop also comprises the ecteniniid cynodont Trucidocynodon riograndensis (Oliveira et al 2010), the early dinosaur Pampadroameus barberenai, and indeterminate dinosauriforms (Müller et al 2014;Pretto et al Forthcoming).…”

New dinosaur remains from the Late Triassic of southern Brazil (Candelária Sequence, Hyperodapedon Assemblage Zone)

“…1), including the typematerial of the sauropodomorph Pampadromaeus and the carnivorous cynodont Trucidocynodon riograndensis (Oliveira et al 2010). The most abundant taxon is the herbivorous cynodont Exaeretodon riograndensis , Liparini et al 2013; however, the presence of rhynchosaurs (Hyperodapedontidae) correlates the fossil suite with the Hyperodapedon Assemblage Zone (sensu Abdala et al 2001) of presumed Ischigualastian age (Langer 2005).…”