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The
Pinnipedia are seals, sea lions, and walrus. For years
there has been discussion about the classification of
Pinnipedia with many scientists including them in Carnivora.
However current evidence, including DNA analysis, indicates
that Pinnipedia is monophyletic but it is not yet been
concluded whether they should be given ordinal ranking
or placed within Carnivora. This account is taken from
Walker's Mammals of the World Vol. 2, 6th edition
which places them in the order Pinnipedia. This order
contains 3 Recent families, 18 genera and 34 species.
Their worldwide distribution encompasses polar to temperate
coastal habitats, with some species inhabiting more
tropical locations and others venturing into inland
waters. The fossil history of Pinnipedia is from the
late Oligocene or early Miocene to Recent in North America,
Pliocene to Recent in South America and Europe, late
Pliocene in Egypt, and Pleistocene to Recent in New
Zealand, Australia and Japan.
The
limbs of Pinnipedia are highly modified for aquatic
locomotion with flattened, elongated and webbed digits.
The name pinniped actually means "feather-footed".
Other aquatic adaptations include streamlined body,
external ears are reduced or absent, slit-like nostrils
that close completely and flexible spines that allow
for impact from waves and hauling out onto land, as
well as agility for catching fleeing prey. Ottariidae
and Odobenidae use their front flippers in an up and
down motion for primary locomotion, whereas Phocidae
use their hind flippers in a side to side motion.
All
of the Pinnipedia are carnivorous and dependant upon
the aquatic environment for food. No matter how aquatic
each species' lifestyle may be, they all must return
to the land to breed, give birth and rear their young.
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