Ursus americanus amplidens Jul 28, 2011 18:54:32 GMT -9
Post by grrraaahhh on Jul 28, 2011 18:54:32 GMT -9
Pleistocene fossil remains: Ursus amplidens, Greene County, Missouri.
Ursus americanus amplidens as first described by Dr. Leidy in 1853.
Pleistocene representatives of living species are frequently found to average larger than their living descendants. This is particularly true for the bears, which are extremely plastic in size (Kurten, 1959). There is thus no reason for a specific separation between the Pleistocene and Recent black bears.
These remarks apply particularly to the black bears of the last or Wisconsin glaciation. The forms of Illinoian date from the Cumberland Cave and the Conard Fissure are distinguished by somewhat smaller size and a slightly more primitive dentition with large carnassials and small back teeth; these early black bears are still very close to the second-glaciation, or Elster, Ursus thibetanus kokeni from China, which is likely to be the ancestral form. The earliest record for Ursus americanus in North America appears to be that from the Port Kennedy Cave (Hibbard, 1958), dating from the Yarmouth; I have not seen this material, and there is no good description. It may be tentatively suggested that the early (Yarmouthian and Illinoian) black bears of America might be regarded as a distinct subspecies, for which the name Ursus americanus vitabilis Gidley, 1914, is available (type locality, Cumberland Cave).
As regards the Wisconsin forms, the proper procedure at present seems to be to take the earliest name and use it as a subspecific designation. This is Ursus amplidens Leidy (1853). As the name indicates, the form was distinguished from the Recent black bears by the large size of the teeth (Table 2). The cotype jaw was noted to be unusually shallow; probably this is due to immature age.