Early Eocene Brontotheriidae (Perissodactyla) from the Eureka Sound Group, Ellesmere Island, Canadian High Arctic—implications for brontothere origins and high-latitude dispersal

Abstract

ABSTRACT The northernmost records of early Eocene brontotheres, fossils of cf. Eotitanops and Brontotheriidae gen. et sp. indet., are described here from late Wasatchian-aged strata of upper parts of the Eureka Sound Group on central Ellesmere Island (~79°N). Although the fossils were initially tentatively identified on faunal lists as Lambdotherium, their larger size and dental morphology ally them more closely to mid-latitude Eotitanops and Palaeosyops. The Ellesmere Island specimens are dentally most similar to mid-latitude Eotitanops, but can be distinguished from the latter by derived characters on their premolars that are shared with the younger (i.e., Bridgerian) Palaeosyops. The presence of brontotheres in early Eocene strata on Ellesmere Island implies that the group's evolution was well underway early in its history at northern high latitudes, and is consistent with either an Asian or North American origin and trans-Beringian dispersal. While cf. Eotitanops from Ellesmere Island appears dentally too advanced to be ancestral to mid-latitude co-eval Eotitanops, it may be a suitable ancestor to Palaeosyops. The presence of cf. Eotitanops on Ellesmere Island may reflect a high-latitude lineage that subsequently dispersed to mid-latitudes during early middle Eocene (Bridgerian) time.