Earliest mammal with transversely expanded upper molar from the Late Triassic (Carnian) Tiki Formation, South Rewa Gondwana Basin, India

Abstract

ABSTRACT A mammalian upper molariform tooth recovered from the Late Triassic (Carnian) Tiki Formation of the South Rewa Gondwana Basin, India, is described as a new taxon, Tikitherium copei, gen. et sp. nov. Coming from such an ancient horizon, the tooth is remarkable in having on its crown, which is supported by three roots, three buccally placed cusps forming an obtuse triangle, another prominent cusp with two associated shearing crests in the posterolingual corner, and a talon-like depression anterior to the latter. The molar with its several derived features, though showing partial similarity with those of some seemingly allied early mammalian dentitions, stands apart as a distinctly different entity in detailed comparison. Through close examination of the Tikitherium upper molar, its probable occlusal relationship with the unknown lower dentition is suggested. The posterolingual cusp with its two shearing crests and basin, appearing as a significant apomorphy, probably indicates the development of a better mode of mastication by grinding. The molar of Tikitherium copei, may thus be regarded as the earliest representative of several independent evolutionary developments of the grinding mechanism found in later mammalian groups such as the boreosphenidans, australosphenidans, shuotheriids, and docodonts.