It is uncertain whether ursids were in Asia during the late Eocene, although there is some suggestion that a limited immigration from Asia may have produced Parictis in North America due to the major sea level lowstand at ca. 37 Ma, but no Parictis fossils have yet to be found in East Asia. Ursids did, however, become very diversified in Asia later during the Oligocene. Four genera representing two subfamilies (Amphicynodontinae and Hemicyoninae) have been discovered in the Oligocene of Asia: Amphicticeps, Amphicynodon, Pachycynodon, and Cephalogale. Amphicticeps is endemic from Asia and the other three genera are common to both Asia and Europe. This indicates migration of ursids between Asia and Europe during the Oligocene and migration of several taxa from Asia to North America likely occurred later during the late Oligocene or early Miocene. Although Amphicticeps is morphologically closely related to Allocyon, and also to Kolponomos of North America, no single genus of the Ursidae is known to be common to both Eurasia and North America. Cephalogale, however, do appear in North America in the early Miocene. It is interesting to note that rodents, such as Haplomys and Pseudotheridomys (late Oligocene) and Plesiosminthus and Palaeocastor (early Miocene), are common to both Asia and North America and this indicates that faunal exchange did occur between Asia and North America during the late Oligocene to early Miocene. Ursid migration from Asia to North America would therefore have also been very likely to occur during this time.[9] Three major carnivoran migrations between Eurasia and North America are recognized in the late Neogene that definitely included ursids. The first around 20 Ma (probably 21–18 Ma) were waves of intermittent dispersals that included Amphicynodon, Cephalogale and Ursavus. The second migration occurred at about 7–8 Ma and included Agriotherium. And the last wave took place in the early Pliocene 4 Ma with Ursus.[10]

The giant panda's taxonomy 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.[11] 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.[12] The status of the red panda remains uncertain, but many experts, including Wilson and Reeder, classify it as a member of the bear family. Others place it with the raccoons in Procyonidae or in its own family, the Ailuridae. The many similarities between the two pandas are thought to represent convergent evolution for feeding primarily on bamboo.

There is also evidence that, unlike their neighbours elsewhere, the brown bears of Alaska's ABC islands are more closely related to polar bears than they are to other brown bears in the world. Researchers Gerald Shields and Sandra Talbot of the University of Alaska Fairbanks Institute of Arctic Biology studied the DNA of several samples of the species and found that their DNA is different from that of other brown bears. The researchers discovered that their DNA was unique compared to brown bears anywhere else in the world. The discovery has shown that while all other brown bears share a brown bear as their closest relative, those of Alaska's ABC Islands differ and share their closest relation with the polar bear.[13] There is also supposed to be a very rare large bear in China called the blue bear, which presumably is a type of black bear. This animal has never been photographed.

Classification:

• Family Ursidae
  • Subfamily Ailuropodinae
    • Giant Panda, Ailuropoda melanoleuca
    • Dwarf Panda, Ailuropoda minor (extinct)
  • Subfamily Tremarctinae
    • Spectacled Bear, Tremarctos ornatus
    • Florida Cave Bear, Tremarctos floridanus (extinct)
    • Giant Short-Faced Bear, Arctodus simus (extinct)
    • Short-Faced Bear, Arctodus pristinus (extinct)
    • Brazilian Short-Faced Bear, Arctotherium brasilense (extinct)
    • Argentine Short-Faced Bear, Arctotherium latidens (extinct)
  • Subfamily Ursinae
    • Brown Bear, Ursus (Ursus) arctos
      • Subspecies Syrian (Brown) Bear Ursus arctos syriacus
      • Subspecies Grizzly Bear, Ursus arctos horribilis
      • Subspecies Kodiak Bear, Ursus arctos middendorffi
      • Subspecies Himalayan Brown Bear, Ursus arctos isabellinus
      • Subspecies Bergman's Bear, Ursus arctos piscator (extinct?)
      • Gobi Bear, Ursus arctos gobiensis(very rare)
      • Atlas Bear, Ursus arctos crowtheri (extinct)
    • American Black Bear, Ursus (Ursus) americanus
      • Subspecies Cinnamon Bear, Ursus americanus cinnamomum
      • Subspecies Kermode Bear, Ursus americanus kermodie
    • Polar Bear, Ursus maritimus
    • Asiatic Black Bear, Ursus (Selenarctos) thibetanus
      • Formosan Black Bear, Ursus thibetanus formosanus
      • Ursus thibetanus gedrosianus
      • Ursus thibetanus japonica
      • Ursus thibetanus laniger
      • Ursus thibetanus mupinensis
      • Ursus thibetanus thibetanus
      • Ursus thibetanus ussuricu
    • Sloth Bear, Melursus ursinus
      • Subspecies Sri Lankan Sloth Bear Melursus ursinus inornatus
      • Subspecies Indian Sloth Bear Melursus ursinus ursinus
    • Sun Bear, Helarctos malayanus
      • Subspecies Borneo Sun Bear Helarctos malayanus euryspilus
    • Auvergne Bear, Ursus minimus (extinct)
    • Etruscan Bear, Ursus etruscus (extinct)
    • European Cave Bear, Ursus spelaeus (extinct)
    • MacFarlane's Bear, Ursus (Vetularctos) inopinatus (cryptid; if a good species, extinct)

The genera Melursus and Helarctos are sometimes also included in Ursus. The Asiatic black bear and the polar bear used to be placed in their own genera, Selenarctos and Thalarctos which are now placed at subgenus rank.

A number of hybrids have been bred between American black, brown, and polar bears (see Ursid hybrids).