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.
Alaska Peninsula brown bear
There is debate as to if Alaska Peninsula brown bears should be referred to as "grizzlies" along with all other North American subspecies of the brown bear. There is confusion experienced when referring to inland and coastal ones separately, but biologists still maintain that coastal ones are truly brown bears. However, it is considered correct to place all North American members of "U. arctos" in the subspecies "horribilis" except the giant Kodiak bears of Kodiak Island. To avoid confusion, many simply refer to all North American members, including Kodiaks, as "grizzly bears."