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The subfamily Aepycerotinae is (and always has been) endemic to Africa,
and is represented by a single living species, the impala. The
impala could easily be the archetypical antelope, its form bearing resemblance
to many other bovids. However, this species also displays numerous
characteristics not found in any other bovid, and few authors dispute its
unique taxonomic position.
The Aepycerotinae appears to be one of the most ancient branches of the
Aegodontia, having diverged from other bovids in the Miocene. The result
is that the Aepycerotinae have had a long independent history, which makes
determining their affiliation with the other subfamilies very difficult (they
are allied here with the Hippotraginae-Alcelaphinae-Caprinae clade, but not
all authors agree with this). The Aepycerotinae first appear in the
fossil record 6.5 million years ago; the impala has not changed considerably
since then (some authors consider the Miocene impala to be the same species
as the modern impala, Aepyceros melampus).
The continued success of this species (and subfamily) is due to its generalist
habits. Impala are not specialized for one mode of food acquisition;
they will graze when grasses are fresh and growing, but will readily browse
on foliage, and even feed on withered leaves during the dry season. This
adaptability in feeding strategies allows the impala is able to live at high
densities in a range of habitats.
Only males bear the strongly ridged horns; they are lyrate in form, long,
and relatively thin. There are no preorbital glands; however, males
have a high concentration of sebaceous glands on the forehead. Unique
among the Bovidae, impala possess metatarsal glands (on the fetlocks, just
above the hooves on the hind legs), which are strikingly marked with a tuft
of black hair. |
