Mid-Cenozoic Rhinocerotid Dispersal via the North Atlantic

Abstract

The North Atlantic Land Bridge (NALB), which connected Europe to North America, enabled high latitude dispersal, particularly during globally warm periods such as the Paleocene-Eocene Thermal Maximum, a period of dramatic faunal reorganization. It has been generally accepted by paleontologists, based on faunal comparisons between Europe and North America, that terrestrial vertebrates did not disperse via the NALB more recently than the early Eocene. Herein, we describe a new Early Miocene rhinocerotid species from the Canadian High Arctic with proximity to the NALB and present novel phylogenetic hypotheses for rhinocerotids. The new species, a member of the genus Epiaceratherium, is differentiated from the four other members of the genus by characteristics of the P3, M1-2, mandible, and lower premolars. Global-scale biogeographic analyses reveal a high number of dispersals between Europe and North America, in both directions; cumulatively, they near the number of dispersals within Eurasia. Notably, multiple dispersals occurred in the Oligo-Miocene, suggesting that the NALB may have been crossable for mammals for at least 20 Ma longer than previously considered, consistent with emerging geological and palaeoclimatological models. We thus provide insight into the importance of the NALB as persistent high latitude connector of geographically disparate terrestrial faunas, underscoring the pivotal role of the Arctic in mammalian evolution.