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Lower Jaw and Dentition of the Hemphillian Bear, Agriotherium (Ursidae), with the Description of a New Species

Walter W. Dalquest
Journal of Mammalogy
Vol. 67, No. 4 (Nov., 1986), pp. 623-631
DOI: 10.2307/1381124
Stable URL: http://www.jstor.org/stable/1381124
Page Count: 9
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Lower Jaw and Dentition of the Hemphillian Bear, Agriotherium (Ursidae), with the Description of a New Species
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Abstract

Agriotherium is known in North America only from middle to late Hemphillian age deposits. The permanent molars of Agriotherium were retained in the jaw until the animal reached full size, and then erupted simultaneously or in swift sequence. In Ursus the first molar erupts when the cub is scarcely old enough to leave the den, and the second and third molars in sequence thereafter. The premasseteric fossa separates Agriotherium from Indarctos and Ursus but is shared by modern to Pleistocene Tremarctos and Arctodus. The lower permanent dentition of Agriotherium has a reduced premolar pattern: P1̄ is present, P2̄ is absent, P3̄ is present in middle Hemphillian A. coffeyi as a two-rooted tooth but absent in the late Hemphillian A. schneideri Sellards. A. gregoryi (Frick) is poorly characterized and may be a synonym of A. schneideri. Agriotherium is not closely related to Indarctos. No known species of Agriotherium appears to have been ancestral to Arctodus or Tremarctos.

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