I’ve known for some time that
giraffes and okapi are related. But in looking up giraffe evolution, I’ve
discovered that giraffes are also (distantly) related to pronghorns, deer, musk
deer, cattle, goats, sheep, wildebeests, and antelope. What a wide-ranging
family! However, the opaki are their closest relative, so close that a
7-million year old fossil had a neck that was a blending of a giraffe neck and
an opaki neck.
Giraffe and opaki ancestors once
roamed all of Eurasia, but in modern times, they are only found in Africa.
Giraffes live in the savanna grasslands, while okapi live in the rain forest.
One possible early ancestor of
giraffes is the Canthumeryx, which lived in Libya. No one is sure when it
lived; guesses range from 25 million years ago to 14.3 million years ago. It
was a medium-sized animal, slender and antelope-like.
About 15 million years ago,
Giraffokeryx appeared in the Indian subcontinent. It may have resembled an
okapi or a small giraffe. It showed some definite lengthening of the neck.
The Sivatherium ranged throughout
Africa and to the Indian subcontinent about 1 million years ago, and may have
gone extinct as recently at 8,000 years ago, as ancient rock paintings greatly
resemble them. The picture of a reconstruction of one show a pair of horns that
look rather like the horns of a Texas longhorn, but only about a foot long each.
The neck wasn’t as long as a modern giraffe, and the spots are depicted as
being not quite so regular. It stood 7.2 feet tall at the shoulder, with a
total height of 9.8 ft and a body weight of up to half a ton. Its shoulders
were very strong to support the neck muscles required to life the heavy skull.
There was another giraffe-type
animal that ranged from India to Turkey called the Bramatherium, which was
closely related to the Sivatherium.
The Shansitherium was a
superficially moose- or antelope-like giraffe from the Shanxi province in
China. They were closely related to the Samotherium, which was rather like a
half-way point between a giraffe and an opaki, as far as size goes.
Giraffes have horns! They are
actually called ossicones, being made of bone and covered in furry skin. Some
of their ancestors had 2, like modern giraffes, and some had 4. Sometimes they
stuck up, or stuck up and curved back, or maybe they stuck out vertically. The
Sivatherium horns as I described looked like small longhorns, did not look to
be covered in furry skin, but they also had a pair of ossicones above their
eyes.
So, if I ever want to make up a
giraffe-like alien creature, I now know there is plenty of leeway for using my
imagination!
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