Today only two
types of proboscidae remain on earth. They are both tropical in
nature, but they come from areas that are quite separate
geographically. One type lives in Asia and one type in Africa.
Although they are superficially similar, it is
actually very easy to tell them apart. In the
pictures above, note that the back of
the Asian Elephant arches upward right from its shoulders to its
hips. The back of the African Elephant slopes down over its
shoulders forming a more gradual arch that rises over the hips.
Additionally, note that the African Elephant has larger ears than
the Asian Elephant, whereas the Asian Elephant has a more pronounced
forehead than the African Elephant. Lastly, both males and females
of African Elephants have pronounced tusks that are clearly
visible. In Asia, you usually don’t see tusks on females.
You can even tell
the species apart by looking at the tips of the trunks alone. The
African Elephant’s trunk has two finger-like projections that it
uses for manipulating material. The trunk of the Asian Elephant has
only one such projection.
Note
the single "finger" on the trunk tip of the Asian Elephant
Their evolutionary
lines of these two elephants have been separate for about 5 million
years. This makes them no more closely related than zebras and
horses. In fact, evidence suggests that Asian Elephants were more
closely related to extinct wooly mammoths of the past than they are
to African elephants of today.
Anatomical similarities suggest the Woolly Mammoth was more closely
related to the Asian Elephant (right) than it was to the African
Elephant (left)
Perhaps that explains why Asian Elephants are sometimes much hairier
than their African counterparts.
photo M. Noonan
It is
an exciting time to be an elephant biologist! Consideration of the
phylogeny and taxonomy of elephants has become even more interesting
lately. Within Africa, there are consistent differences between the
elephants that inhabit the savannah and those elephants that inhabit
thick forests. At the very least, these two types can be recognized
as different subspecies. However, the differences are great enough
that many elephant biologists now consider it reasonable to classify
these African elephants as two entirely separate species: the
Savannah African Elephant and the Forest African Elephant. If this
idea gains widespread support, we may soon say we have three
species of living proboscidae -- two in Africa and one in Asia.