The order under which Elephants are classified is the Proboscidea. This is for one of the elephant's most interesting physical features. It is something that attracts curiosity from around the world for elephants along with many other aspects in the past only ascribed to the human, such as, rudimentary tool use, complex social behaviours, and reverence for a dead family member or friend. It is their trunk or proboscis; the meaning of Proboscidea species is simply animals with trunks/proboscis. Henry F. Osborn identified some 352 proboscidean species and subspecies of which only half are recognized and valid today (Elephants: the animal and its ivory in African culture). About 50-60 million years ago, the ancestors of the modern elephant occupied a variety of extreme environments; this includes from tropical rain forests to deserts in both low and high altitudes. Incredibly, with the exception of Australia and Antarctica, the proboscideans have over time inhabited every single continent on Earth. Why did all but two become extinct? One possible explanation for their disappearance may be found in the inability of the order to evolve to environmental change fast enough. One of the determining factors in this is the more specialized a particular genus of animals, then the more likely they they will become extinct in periods of dramatic climate and environmental change. Both of the surviving African and Asian elephants have a wide range of attributes which give them the ability to survive and to even thrive in mild to extreme environmental conditions. Obviously, this is probably not the only reason for the disappearance of most of the order, but serves as a good generalization for a reason why the multiple families of the order disappeared over time.