Cretaceous Mammal Skulls from Mongolia

Abstract

THE discovery of Cretaceous mammal skulls in Mongolia by the Central Asiatic Expedition of the American Museum of Natural History is an event of exceptional importance in vertebrate palaeontology. The Cretaceous forerunners of the varied placental mammals of the Palaeocene and Eocene have hitherto been known only by inference. The studies of Cope, Osborn, Wortman, Matthew, and others upon the dentition and skeleton of Eocene mammals led to the view that the earliest insectivores and creodonts, taken collectively, were descendants of the most primitive group of placentals, for which the name Therict-oidea was proposed by Gregory in 1910.¹ It was further inferred that the stem placentals of the Cretaceous would be more or less intermediate in character between the Jurassic “Amphitherium” and such early Eocene forms as Palseoryctes, Didelphodus, and the Oxyctenidæ.²