Cosmopolitanism among Gondwanan Late Cretaceous mammals

Abstract

Consistent with geophysical evidence for the breaking up of Pangaea, it has been hypothesized that Cretaceous vertebrates on progressively isolated landmasses exhibit generally increasing levels of provincialism, with distinctly heightened endemism occurring at the beginning of the Late Cretaceous. The Cretaceous fossil record from the southern supercontinent of Gondwana has been much too poor to test this hypothesis with regards to mammals (Fig. 1). Early Cretaceous mammals are known only from isolated sites in Argentina, Australia, Cameroon and Morocco. Apart from several occurrences in South America, knowledge of Late Cretaceous Gondwanan mammals is limited to a single site in India that previously yielded a few specimens of placental mammals, and a site in Madagascar that previously yielded only one indeterminate tooth fragment. Here we report the occurrence of a highly specialized and distinctive group of extinct mammals, the Sudamericidae (Gondwanatheria), in the Late Cretaceous of Madagascar and India. These new records comprise the first evidence of gondwanatheres outside South America and the first indication of cosmopolitanism among Late Cretaceous Gondwanan mammals. Antarctica may have served as an important Cretaceous biogeographic link between South America and Indo-Madagascar.