The subfamily Caprinae,[1] also sometimes referred to as the tribe Caprini,[2] is part of the ruminant family Bovidae,[3] and consists of mostly medium-sized bovids.Although most goat-antelopes are gregarious and have fairly stocky builds, they diverge in many other ways – the muskox (Ovibos moschatus) is adapted to the extreme cold of the tundra; the mountain goat (Oreamnos americanus) of North America is specialised for very rugged terrain; the urial (Ovis orientalis) occupies a largely infertile area from Kashmir to Iran, including much desert country.No sharp line divides the groups, but a continuum varies from the serows at one end of the spectrum to sheep, true goats, and musk oxen at the other.[5] The group did not reach its greatest diversity until the recent ice ages, when many of its members became specialised for marginal, often extreme, environments: mountains, deserts, and the subarctic region.The ancestors of the modern sheep and goats (both rather vague and ill-defined terms) are thought to have moved into mountainous regions – sheep becoming specialised occupants of the foothills and nearby plains, and relying on flight and flocking for defence against predators, and goats adapting to very steep terrain where predators are at a disadvantage.