An Unusual Ungulate Jaw from the Pliocene of Texas

Abstract

Recent excavations at the Coffee Ranch quarry, nine miles north of Miami, Hemphill County, Texas, have yielded a quantity of fossil bones of early-middle Pliocene age. This site is the locality 20 of Reed and Longnecker (1932) and probably has furnished the best known sample of the Hemphillian fauna (see Matthew and Stirton, 1930a, 1930b, Burt, 1931, Matthew, 1932). Where worked by Midwestern University, there is a layer of volcanic ash more than 6 feet in thicknss, and dirctly under the ash bed a layer of glauconitic clay varying from one to four feet in depth. Beneath the clay bed is an unconsolidated greenish sand, six feet or more in thickness and with numerous pockets rich in fossil bones. Past workers seem to have devoted most attention to the greenish sand layer. The clay bed contains numerous fragments of fossil bones, mostly greatly broken and rarely more than a fraction of an inch in diameter. Among the fragments of larger bones are some teeth and jaw fragments of insectivors, rabbits, rodents and small carnivors, with an occasional tooth or jaw of a larger mammal. Through the kindness of the Hardin Foundation of Wichita Falls, Texas, and the Midwestern University Faculty Research Committee, funds were made available to permit the quarrying and washing of the clay, to recover the remains of small mammals present. In the course of quarrying operations, a most unusual ungulate lower jaw was discovered. The incisors and the extreme anterior tip of the jaw are missing, as is the ramus posterior to the last molar. The cheek-tooth dention, however, is complete. The teeth had all been broken off just above the roots, and were firmly encased in clay matrix. The remainder of the jaw was collected in another large piece of clay. The breaks were clean and the teeth fitted closely to the broken roots. The jaw is unusual in the presence of alveoli for seven cheekteeth. As exposed when first discovered, the roots showed clearly and all four premolars have double roots. In the laboratory, the jaw was sketched before the teeth were restored (fig. 1).