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Wild Animals - Bears
morphology related to its diet on termites and ants no later than by the early Pleistocene. By 3-4 Ma ago, the species Ursus minimus appears in the fossil record of Europe, which apart from size is nearly identical to today's Asiatic black bear. It is likely ancestral to all bears within Ursinae, perhaps aside from the sloth bear. Two lineages evolved from U. minimus, the black bears (including the sun bear, the Asiatic black bear, and the American black bear), and the brown bears. Modern brown bears evolved from U. minimus via Ursus etruscus, which itself is ancestral to both the extinct Pleistocene cave bear and the ancestor of today's brown and polar bears. Species of Ursinae have migrated repeatedly into N. America from Eurasia as early as 4 Ma ago during the early Pliocene. The fossil record of bears is exceptionally good. Direct ancestor-descendent relationships between individual species are often fairly well-established, with sufficient intermediate forms known to make the precise cut-off between an ancestral and its daughter species subjective. Other extinct bear genera include Agriarctos, Indarctos, and Agriotherium (sometimes placed within hemicyonids).
The giant panda's taxonomy (subfamily Ailuropodinae) has long been debated. Its original classification by Armand David in 1869 was within the bear genus Ursus, but in 1870 it was reclassified by Alphonse Milne-Edwards to the raccoon family. In recent studies, the majority of DNA analyses suggest that the giant panda has a much closer relationship to other bears and should be considered a member of the family Ursidae. Estimates of divergence dates place the giant panda as the most ancient offshoot among living taxa within Ursidae, having split from other bears 17.9 to 22.1 Ma ago. The red panda was included within Ursidae in the past. However, more recent research does not support such a conclusion and instead places it in its own family Ailuridae, in superfamily Musteloidea along with Mustelidae, Procyonidae, and Mephitidae. Multiple similarities between the two pandas, including the presence of false thumbs, are thus thought to represent an example of convergent evolution for feeding primarily on bamboo. There is also evidence that, unlike their neighbors elsewhere, the brown bears of Alaska's ABC
Taxonomic revisions of living bear species