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

Autor:	Walter W. Dalquest
Rok vydání:	1986
Předmět:	Tremarctos Ecology Dentition biology Fossa Anatomy biology.organism_classification Mandibular first molar medicine.anatomical_structure Genetics Premolar medicine Animal Science and Zoology Ursus Agriotherium Ecology Evolution Behavior and Systematics Nature and Landscape Conservation Indarctos
Zdroj:	Journal of Mammalogy. 67:623-631
ISSN:	0022-2372 1545-1542
DOI:	10.2307/1381124
Popis:	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: P1 is present, P2 is absent, P3 is present in middle Hemphillian A. coffeyi as a two-rooted tooth but absent in the late Hemphillian A. schneiden Sellards. A. gregoryi (Frick) is poorly characterized and may be a synonym of A. schneiden. Agriotherium is not closely related to Indarctos . No known species of Agriotherium appears to have been ancestral to Arctodus or Tremarctos .
Databáze:	OpenAIRE
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