Mandibular and dental characteristics of Late Triassic mammaliaform Haramiyavia and their ramifications for basal mammal evolution

The origins and earliest evolution of mammals can be deciphered by studying Late Triassic fossil relatives of modern mammals. The computed tomography study of Haramiyavia from the Late Triassic has revealed new information about the skull evolution and dental function in the forerunners of mammals. Haramiyavia had a unique way of chewing. Its teeth of multiple cusp-rows were adapted to omnivory or herbivory and are distinctive from the teeth of other early mammal relatives that are presumed to be insectivorous. On the mammal family tree Haramiyavia occupies a position crucial for dating the initial appearance of the major mammalian groups. Our reanalysis affirms that the earliest diversification of mammals occurred in the Jurassic.