The Anthracotheriidae (Mammalia; Artiodactyla) from the Eocene Pondaung Formation (Myanmar) and comments on some other anthracotheres from the Eocene of Asia

Abstract

We reevaluate the classifications of the anthracotheres (Mammalia; Artiodactyla) from the latest middle Eocene Pondaung Formation (central Myanmar), mentioning other anthracotheres from the Eocene of Asia. The three anthracotheriid genera previously known from the Pondaung Formation, Anthracothema, Anthracokeryx, and Anthracohyus, are synonymized into Anthracotherium. As many as 13 species had been recognized in the Pondaung anthracotheres, but they are summarized into four species (Anthracotherium pangan, Anthracotherium crassum, Anthracotherium birmanicum, and Anthracotherium tenuis), based on the difference of M₁ size (∼ body size). Dental morphology in each species indicates high variation, and the four species are not separable based on their dental morphology. The dental morphology of the Pondaung Anthracotherium species is distinct from that of other species and is the most primitive. In addition, the Pondaung Anthracotherium species are the oldest of the genus. The genus Anthracotherium might have originated and rapidly radiated around the Pondaung area during the latest middle Eocene. Siamotherium pondaungensis described from the Pondaung Formation as an anthracotheriid is synonymized to Pakkokuhyus lahirii (Artiodactyla; Helohyidae).