Fauna and correlation of the Gashato Formation of Mongolia

Iw the Gurbun Saikhan piedmont basin, just north of the eastern end of the Altai Mountains, there are two distinct formations. The lower of these is the Djadochta formation of Cretaceous age and contains abundant remains of the primitive horned dinosaur Protoceratops and its eggs. Resting unconformably upon these Cretaceous beds is a series of not less than two hundred feet of reddish and drab sediments to which the naxne Gashato has been assigned and which yielded the interesting primitive mammalian fauna herein described. The exposures of the Gashato beds are of rather limited extent in the type locality, which is near Shabarakh Usu on the KweihwatingUliassutai trail, and are only very sparingly fossiliferous. Mr. F. K. Morris, while studying the stratigraphy of the beds, discovered the first mammalian remains, and later Mr. George Olsen, with an assistant, spent several days there. The fragmentary and weathered remains of the largest form, Phenacolophus, were all found within a small area, and the rest of the collection, all diminutive forms, came from two small knolls not far distant. A most careful examination of the entire exposure resulted in no further discoveries. The fauna is later than Lower Cretaceous, and there can be scarcely any question that it is older than the Irdin Manha, Upper Eocene. The faunal list follows. Palmeostylops iturus Order Notoungulata Prionessus lucifer " Multituberculata Baenomys ambiguus " Glires Eurymylus laticeps " ? Menotyphla Phenacolophus fallax " ? Condylarthra Hyracolestes ermineus " Creodonta Sarcodon pygmaus " uncertain (?creodont or carnivorous marsupial)