Tetraceratops

Tetraceratops

• North America (Texas )

Tetraceratops is an extinct genus synapsider land vertebrates and possibly the most primitive Therapside ( formerly known as " mammal -like reptiles ") is. She lived during the Permian. Only species described is Tetraceratops insignis. The at Wichita River in Baylor County ( North Texas ) holotype found by the U.S. fossil collector and amateur paleontologist Charles Sternberg Hazelius, incomplete, crushed skull is preserved in the American Museum of Natural History in New York. He is still the only fossil of the genus.

Features

The skull is short, only ten inches long and high. A pair of short, bony outgrowths are located in the premaxilla above the nostrils and on the Präfontale before the eyes, Tetraceratops means " Four -horned face ". Tetraceratops thus resembles the Burnetiidae in which the excesses are, however, formed by another bone. Two other excesses that were not known when the first description can be found on the side of the two angular bones that in primitive land vertebrates a portion of the lower jaw form and have become in mammals to ossicles. The dentary is the largest single bone of the mandible. The lacrimal bone ( lacrimal ) forms the front part of the eye socket (orbit ).

The dentition has Tetraceratops than meat eaters. The first two cutting teeth on the premaxilla are very much larger than the four following. There is a toothless gap ( diastema ) between the teeth on the premaxilla and those of the maxilla. In the maxilla there are large canine teeth, the teeth behind them have sharp, curved crowns. On a rear wing outgrowth of the bone ( pterygoid ), a part of the palate, there are six large teeth. Before the outer wing strut ( Ectopterygoid ) the dentition ends.

System

Tetraceratops 1908 was described by William Diller Matthew as the new Pelycosaurier, which is closely related to the Sphenacodontidae. Alfred Romer and Llewellyn Price arranged the genus Eothyrididae 1940, another little-known Pelycosaurierfamilie to. In 1996, Michael Laurin and Robert R. Reisz Tetraceratops because of some cranial features to the therapsids. If this assessment is correct, Tetraceratops is to be regarded as the oldest and most primitive Therapside. Phylogenetically, it could be the sister genus of all other therapsids. Between Tetraceratops and the first in Russia and South Africa fossil proven safe Therapsid there is a gap of 10 million years ago. J. Conrad and C. Sidor found again in 2001 hints that he should be classified as Sphenacodontidae. Some diagnostic features of the therapsids can not be checked at Tetraceratops because the skull is to get incomplete. Tetraceratops can be classified as a mosaic form between Pelycosauriern and therapsids.