The "hyrachyid" ceratomorph Subhyrachyus tshakpaktasensis Gabuniya, was named for a nearly complete skull from the Zaysan Basin of eastern Kazakstan. This skull is from the Eocene (Arshantan) Chakpaktas Formation at the Mozhevelnik locality on the Kalmakpay River. Re-examination of the skull indicates it belongs to the lophialetid genus Eoletes Biryukov, based on the following diagnostic features: shallow nasal incision only retracted to above the canine, long and shallow maxillary fossa, anterior edge of orbit above M2, no modifications of rostrum as in Lophialetes, short postcanine diastema, complete u-shaped lophoid loops on P3-4, and relatively lophodont cheek teeth. The features that distinguish E. tshakpaktasensis from E. gracilis Biryukov, (type species of Eoletes) and Chinese E. xianensis Zhang & Qi, are minor (upper cheek teeth relatively wider and more prominent premolar ectoloph ribs in E. tshakpaktasensis), but we retain all species as valid pending a larger sample with which to document better dental variability in Eoletes. E. tshakpaktasensis is the first record of Eoletes from the Zaysan Basin and extends the temporal range of the genus from the Irdinmanhan back to the Arshantan.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the Biological Society of Washington|
|State||Published - Dec 1 2001|
All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)