The mammalian faunas of the Paleocene of central Utah, with notes on the geology.
The Oligocene division has been generally accepted as a distinct period, but “Paleocene” is not so widely used.
This collection was obviously of Torrejonian or middle Paleocene age.
Perhaps, this high ratio reflects the imperfectly carnivorous habits of the Paleocene creodonts as a group.
The earliest epoch of the Tertiary Period, from about 65 to 58 million years ago. During this time, the Rocky Mountains formed and sea levels dropped, exposing dry land in North America, Australia, and Africa. Many new types of small mammals evolved and filled the niches left empty after the extinctions that ended the Cretaceous Period. Soft-bodied squid replaced the ammonites as the dominant form of mollusk. See Chart at geologic time.