ON THE ORIGIN OF THE ORDER ARTIODACTYLA

The first known members of the order Artiodactyla appeared suddenly th roughout the Holarctic region at the beginning of the Eocene. They are characterized by distinctive cursorial skeletal specializations. Owin g to their abrupt appearance and the lack of transitional forms, the o rigin of the order is problematic Descent from a ''condylarth,'' speci fically the arctocyonid Chriacus, has been suggested based on dental r esemblances, but until now postcranial anatomy seemed to preclude clos e relationship between Arctocyonidae and Artiodactyla. A middle Paleoc ene specimen of a small arctocyonid (?Chriacus) reported here is much more similar to the oldest artiodactyl, Diacodexis, in the derived con dition of the hindlimb, reviving the possibility that Artiodactyla evo lved from an arctocyonid.