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
The sun bear's fur is usually jet-black, short, and sleek with some under-wool; some individual sun bears are reddish or gray. Two whirls occur on the shoulders, from where the hair radiates in all directions. A crest is seen on the sides of the neck and a whorl occurs in the centre of the breast patch. Always, a more or less crescent-shaped pale patch is found on the breast that varies individually in colour ranging from buff, cream, or dirty white to ochreous. The skin is naked on the upper lip. The tongue is long and protrusible. The ears are small and round, broad at the base, and capable of very little movement. The front legs are somewhat bowed with the paws turned inwards, and the claws are cream.