Taxonomic identification of isolated phytosaur (Diapsida, Archosauria) teeth from the Upper Triassic of India and their significances

Abstract

ABSTRACT Numerous isolated teeth recovered from the Upper Triassic Tiki Formation of India have high, cylindrical, triangular to conical crowns with serrated mesial and distal carinae, and oval/subcircular and elliptical crown bases. Within this overall morphology, the teeth are subdivided into six morphotypes based on crown proportions, nature of carinae and serration and crown-base ratios. These ziphodont teeth are compared with those of other dominant Late Triassic carnivores of India to show similarity with that of the phytosaurs based on their shape, recurved nature, crown proportions, the presence of carina(e), nature of serrations and serration density. The different morphotypes reflect positional heterodonty, and three upper jaw dental sets are identified. This finding is corroborated by PCA, where the morphotypes form distinctly separate clusters, though partial overlapping of these convex hull polygons suggests that these teeth belonged to a single phytosaur taxon. As tripartite dentition is a derived condition; it may be concluded that these isolated teeth belonged to a more derived phytosaur, yet to be recovered from the Tiki Formation. The study highlights the importance of examining isolated teeth in order to identify the fossil forms which are yet to be discovered.