A new dichobunoid artiodactyl from the middle Eocene of Yunnan, China

Abstract

Dichobunoids were the most basal artiodactyl group, widely distributed throughout the Eocene of Eurasia and North America, but were rarely reported from southern China. In this paper, we report the first dichobunoid artiodactyl, Shilinhyus chowi n. gen. n. sp., from the middle Eocene of Lunan Basin (Shilin County), China. Shilinhyus is characterized by its relatively large size, bunoselenodont tooth morphology with a highly developed p4 metaconid, and a mesially interrupted paracristid formed by a weak premetacristid and a strong preprotocristid. This morphology distinguishes Shilinhyus from all known dichobunoid artiodactyls. Within dichobunoids, Shilinhyus resembles Pakkokuhyus from the Eocene of Southeast Asia and “Gobiohyus” yuanchuensis from the Eocene of Shanxi, China, by the relatively large size, the absence of the paraconid, and the well-development of the hypolophid. However, Shilinhyus still differs from Pakkokuhyus and “Gobiohyus” yuanchuensis in the complete interruption of the paracristid and in the alignment of the entoconid and hypoconid as well as the protoconid and metaconiod. Shilinhyus, Pakkokuhyus, and “Gobiohyus” yuanchuensis might have derived from the Eocene Gobiohyus from northern China, constituting a distinct group. The discovery of Shilinhyus chowi enhances our understanding of the early evolution of dichobunoid artiodactyls, especially in southern China.