On the postcanine dentition of Pascualgnathus polanskii Bonaparte (Cynodontia: Traversodontidae) from the Middle Triassic of Argentina

AGUSTIN MARTINELLI

GEOBIOS

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Lugar: Paris; Año: 2010 vol. 43 p. 629 - 638

0016-6995

The dental morphology of Pascualgnathus polaskii Bonaparte (Therapsida, Eucynodontia, Traversodontidae), from the Middle Triassic Río Seco de la Quebrada Formation (Puesto Viejo Group, Argentina), is described and compared with that of other basal traversodontid cynodonts. Albeit Pascualgnathus is frequently used in phylogenetic analyses, neither detail description nor drawings of its postcanines have been published. The upper postcanines of Pascualgnathus are transversely wide, rectangular in occlusal view, with a lingual cusp connected to the transverse ridge which is located in the center of the crown, and one main labial cusp followed by one posterior labial, both forming the labial margin. The lower postcanines, mostly worn out in the known specimens, are quadrangular until pc6 and then they are rectangular with the major axis anteroposteriorly oriented. They have a tall mesial border, possible constituted by one labial and one lingual cusp, and a transverse ridge. After comparisons, the number of cusps in the sectorial, labial border of the upper gomphodont teeth, frequently used in phylogenetic analyses, would not necessary implies real homologies. For example, taxa with postcanines with only one or more cusps anterior to the main labial cusp would not be homologous to taxa with one or more cusps posterior to the main labial cusp, but resulting in a similar count of labial cusps.