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 describe d from the Late Eocene of Krabi in South Thailand. This new form, Prog enitohyus thailandicus n.g. n.sp., is distinct from Gobiohyus, a speci alized genus from the Middle Eocene of Mongolia, and it displays stron g affinities with the primitive anthracotheriid Siamotherium krabiense from Krabi. Both Thai species certainly testify to an ancestor-descen dant relationship, but an even earlier differentiation of Helohyidae a nd Anthracotheriidae should be searched for in the Middle Eocene or ev en earlier.