The taxonomic status of Parathrinaxodon proops (Therapsida: Cynodontia), with comments on the morphology of the palate in basal cynodonts
Date
2005
Authors
Abdala, Fernando
Allinson, Matthew
Journal Title
Journal ISSN
Volume Title
Publisher
BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH
Abstract
The holotype and only specimen of Parathrinaxodon proops, a cynodont from the Upper Permian Kawinga Formation, Tanzania, is
redescribed. Upper postcanines from the middle of the tooth row are ovoid in outline, presenting a large main cusp and tiny anterior
and posterior accessory cusps on the sectorial margin. Anterior and posterior lingual cusps on the crown indicate the presence of a
lingual cingulum. The overall postcanine morphology is remarkably similar to that of Procynosuchus delaharpeae, a Late Permian
cynodont particularly common in the lower Beaufort Group of South Africa. The presence of a complete osseous palate and a medial
palatal opening between the maxillae (=vomerine fossa) in Parathrinaxodon proops remain the main differences previously reported
between this species and Procynosuchus delaharpeae. Restudy of the palate of Parathrinaxodon proops indicates that there exists some
degree of deformation, particularly notable in the broken and distorted vomer. The supposed presence of the complete secondary
palate and of the medial palatal opening in Parathrinaxodon proops are interpreted as resulting from a slight horizontal displacement of
the long, and originally free, palatal processes of the maxilla and palatine. It is concluded that Parathrinaxodon proops is synonymous with
Procynosuchus delaharpeae. This synonymy is problematic because Parathrinaxodon proops Parrington 1936 would have priority over
Procynosuchus delaharpeae Broom 1937, but the latter is the best known Late Permian cynodont. Consequently, we propose to conserve
Procynosuchus delaharpeae as the valid name for this cynodont based on article 23, section 9 (Reversal of precedence) of the International
Code of Zoological Nomenclature. An analysis of the Kawinga fauna, using genus as the taxonomic unit for comparison, indicates
strong similarity (67%) with faunas from theTropidostoma, Cistecephalus and Dicynodon assemblage zones from the SouthAfrican Karoo.