Asian black bear
Biologically and morphologically, Asiatic black bears represent the beginning of the arboreal specializations attained by sloth bears and sun bears. Asiatic black bears have karyotypes nearly identical to those of the five other ursine bears, and, as is typical in the genus, they have 74 chromosomes. From an evolutionary perspective, Asiatic black bears are the least changed of Old World bears, with certain scientists arguing that it is likely that all other lineages of ursine bear stem from this species. Scientists have proposed that Asiatic black bears are either a surviving, albeit modified, form of "Ursus etruscus", specifically the early, small variety of the Middle Villafranchian (Upper Pliocene to Lower Pleistocene) or a larger form of "Ursus minimus", an extinct species that arose 4,000,000 years ago. With the exception of the age of the bones, it is often difficult to distinguish the remains of "Ursus minimus" with those of modern Asiatic black bears.
Sun bear
Sun bears are found in the tropical rainforest of Southeast Asia ranging from northeastern India, Bangladesh, Myanmar, Thailand, Peninsular Malaysia, Laos, Cambodia, Vietnam to southern Yunnan Province in China, and on the islands of Sumatra and Borneo in Indonesia. They now occur very patchily through much of their former range, and have been extirpated from many areas, especially in mainland Southeast Asia. Their current distribution in eastern Myanmar and most of Yunnan is unknown.
The bear’s habitat is associated with tropical evergreen forests."Helarctos anmamiticus", described by Pierre Marie Heude in 1901 from Annam, is not considered a distinct species, but is subordinated (a junior synonym) to "H. m. malayanus".