First discovery of Helohyidae (Artiodactyla, Mammalia) in the Late Eocene of Thailand: a possible transitional form for Anthracotheriidae

Dental remains of the earliest known helohyid artiodactyl are described from the Late Eocene of Krabi in South Thailand. This new form, Progenitohyus thailandicus n.g. n.sp., is distinct from Gobiohyus, a specialized genus from the Middle Eocene of Mongolia, and it displays strong affinities with the primitive anthracotheriid Siamotherium krabiense from Krabi. Both Thai species certainly testify to an ancestor-descendant relationship, but an even earlier differentiation of Helohyidae and Anthracotheriidae should be searched for in the Middle Eocene or even earlier.