The Artiodactyl group must have quickly branched in turn, as we find very primitive hogs and camels before the end of the Eocene.
Eocene, miocene, pliocene Tuff, Lias and Trias and that is enough.
By the end of the Eocene a three-toed genus of the horse family had appeared, as large as a sheep.
Prestwich, Mr., on English and French Eocene formations, 328.
He may even have lived in the Miocene or Eocene period, when not a single mammal was identical in form with any existing species.
But the mammals are the most interesting vertebrates of the Eocene period.
Throughout the Eocene from the London clay onward the shells are such as abound in the warm sea south east of Asia.
Species much like Rhinobatus occur in the Cretaceous and Eocene.
The next geological formation which is represented is the Eocene, consisting of nummulitic limestone, sandstone and schist.
The lowest Eocene deposits in the county are the Reading Beds.
The second epoch of the Tertiary Period, from about 58 to 37 million years ago. During the earliest part of this epoch, land connections existed between Antarctica and Australia, between Europe and North America, and between North America and Asia, and the climate was warm. The land connection between Antarctica and Australia disappeared in the mid-Eocene and early Oligocene, resulting in a change in the predominant oceanic currents and a cooler climate. With this change, the average size of mammals changed from less than 10 kg (22 lbs) to more than 10 kg. The Himalayas also formed during the Eocene, and most modern orders of mammals appeared. See Chart at geologic time.