Ancient Arctogaea

Artiodactyla.

General discussion of the past distribution of the artiodactyls is rendered difficult by the uncertainty which exists as to the classification of that group.

In the Lower Eocene of North America and Europe occur the most primitive forms, and their successors in the Middle and Upper Eocene are similar in these two regions, but in Upper Eocene times certain special groups make their appearance which are restricted to one or other of the two continents. In North America the ancestors of the camels are found at this time and the entirely American family of the oreodonts is represented. In Europe the Anoplotheriidae take the place of these latter forms, and the long-lived family of the Anthracotheriidae appears as small animals.

In the Oligocene the descendants of all these groups are found and a strange creature Elotherium, resembling a gigantic long-legged pig, is represented by very similar forms from both sides of the Atlantic. In this period both in Europe and North America there are peccary-like creatures, and perhaps true pigs in Europe : the anthracotheres reached America at this time but only one of the very large number of European and Indian genera ever reached that continent.

In the Lower Miocene in Europe and Baluchistan there was an amazing variety of anthracotheres ranging from forms as small as a sheep to great creatures as big as a hippopotamus. The last rep resentative of the anthracotheres occurs in rocks of probable Upper Pliocene age in India and Tunis.

It is quite possible that the hippopotamus arose from the anthracotheres. The animal is clearly of Oriental origin, reaching north Africa and Europe in the Upper Pliocene, and being wide spread over Java, India, Europe, Africa and Madagascar in Pleistocene times.

The camels carried out the whole of their evolution in North America in which they are now extinct. They first left that continent in Lower Pliocene times, a large member of the group occurring in the Lower Pliocene of China, and in India in rocks perhaps of somewhat later date. The llamas reached South America in the Pliocene and a llama-like form survived in North America into Pleistocene times.

The higher artiodactyls (Pecora) are represented in the Upper Eocene of Europe and North America by small animals resem bling the existing tragulines. This group of primitive artiodactyls

includes one animal Archaeomeryx from the Upper Eocene of Mongolia, which is the earliest known form capable of being regarded as a direct ancestor for the Pecora. In Oligocene deposits in Europe, and in Lower Miocene times in Europe and North America occur the remains of animals which are more certainly deer. Deer have a continuous representation in both continents from that time to the present day but the earlier American forms appear to be related to the Virginian deer and its allies, the typical genera being of Asiatic and European origin. The antelopes and their allies first appear in the Lower Miocene of Europe, and the group appears to be definitely of Old World origin. It is abun dantly represented in the Pontian fauna from China to Spain and is now the most conspicuous element in the Ethiopian region. Antelopes first appear in North America in the Upper Miocene, but are extremely rare there. The history of the group is however still uncertain. The true oxen are clearly derivatives of the antelopes, and the earliest known and most primitive forms occur in the Lower Pliocene of India : they reached Europe in Upper Pliocene times and America only in the Pleistocene. The ancestry of the goats and sheep is still uncertain but the first definite mem bers of the group appear in the Pliocene of India. In North America from the Middle Miocene to the present day there occurs a distinct family of Pecora, the Antilocapridae, represented now only by the prong-horned antelope. No member of the group has ever been found elsewhere.

According to Pilgrim, the earliest known relative of the giraffe is found in the Lower Miocene of Baluchistan : in the Lower Pliocene the group is represented by very varied forms, some gigantic, some indistinguishable from the living giraffes and others nearly similar to the okapi. These occur throughout the entire distribution of the Pontian fauna from China, Persia, South Russia, Samos and Pikermi. Their remains are not found in German deposits of the same age. No fossil giraffes are known from Africa, the only continent at present inhabited by the family, nor did any member of the group ever reach North America.