The evolution of the elephant : as illustrated in the Yale collections / by Richard S. Lull.

  • R. S. Lull
Date:
[1908]
Catalogue details

Licence: In copyright

Credit: The evolution of the elephant : as illustrated in the Yale collections / by Richard S. Lull. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the symphysis, and the lower tusks point directly forward as in Mceritherivm. The proboscis possibly did not extend beyond the lower tusks while at rest, though it could probably be extended be- yond them. The premolar teeth have two while the molars have three trans- verse crests composed of distinct tubercles and the cingulum of the hindermost tooth shows a strong tendency to form yet an- other crest. There were twenty-six teeth Fig- 15- Tooth of Pa- altogether. The neck is still fairly long, <Eomastoc on (x Al- though the hinder neck vertebrae are beginning to shorten. Ralceomastodon is confined to the Upper Eocene, and has thus far been found only in the Fay urn region. The Yale collection includes full-sized restorations of the skulls of Moeritherium and Ralceomastodon as well as casts of the type specimens, gifts of the British Museum of Natural History. Classification of the Later Proboscidea. We know as yet no Oligocene proboscidians, the next forms being found in the lower Miocene of northern Africa and Europe, so that a considerable break occurs in the continuity of our series. It is evident that the line was still African in distribution, for apparently the exodus from Egypt did not occur before Miocene times. The mastodons have been divided in two ways, one depend- ing upon the number of ridges borne upon the grinders, while the other classification is based upon the number and char- acter of the tusks. The latter seems the more logical from a developmental viewpoint. The first of these genera is Tetrabe- lodon, with four, enamel-banded tusks. The second is Dibeloclon, having but two tusks which still retain the band of enamel. The last genus is Mammut, with enameless upper tusks in the adult, though one or two may also be present in the adolescent lower jaw. The latter are sometimes retained throughout life. Tetrabelodon. The third recorded stage in the evolution of the elephants is represented by the Miocene Tetrabelodon angustidens, of which a splendid specimen from Gers, France, is preserved in the museum of the Jardin des Plantes at Paris. It was an animal of considerable size, nearly as large as the Indian ele- phant, but differing markedly from the latter in the peculiar character, of the lower jaw, which was enormously long at the symphysis and contained a pair of relatively short tusks. This form represents the culmination of the jaw elongation, for in its successors the symphysis is rapidly shortened and the infe-