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The
classification of the Primates order has been disputed
and rearranged several times and has yet to be completely
resolved. In the Primates chapter of Walker's Mammals
of the World, 6th edition, 15 families (including
2 recently extinct families), 77 genera and 279 species
are presented.
The
Homo sapien species in the Primates order has
a worldwide distribution. The other members of Primates
have a more limited range and are distributed from southeastern
Mexico to Argentina and southeastern Brazil. They are
present in most of Africa, to the Arabian Peninsula
and on Madagascar. They inhabit Asia, including Japan
and the East Indies.
What
is known about the fossil history is Paleocene to Recent.
Many of the ancestral relationships including the origination
and subsequent radiation of species are also disputed.
The
development of the cerebral hemisphere in the primate
brain is a characteristic that sets primates apart from
the other mammal species. Other identifying characteristics
include skull shape and size, as well as the presence
of encircling bone around the orbits. Most Primates
have an opposable first digit on each hind foot and
each hand. The exception is Homo sapiens in which
only the first digit of the hand is opposable.
The
size range within the Primate order is extreme with
the smallest species weighing only 30 grams and the
largest weighing up to 200 kg.
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