BIG DO CROCODILES GET?
February 12, 2012
written recently about two animals, pythons and coyotes, that are known
to have attacked and killed people. I have just learned of another that
sounds far more terrifying--a species of giant crocodile known as "shieldcroc"
with a head five feet long and a total length of 30 feet. Most people
will rest easier knowing the species is now extinct, having disappeared
about 100 million years ago in northern Africa, and will not take up
residency in southern states, as Burmese pythons and coyotes have.
Casey M. Holliday, an anatomist with the University of Missouri School
of Medicine, and Nicholas M. Gardner of Marshall University, described
the creature based on a specimen from the Royal Ontario Museum in Toronto.
The common name, shieldcroc, comes from the thick, shieldlike covering
of skin on top of the huge snout. Scientists can only speculate about
the function of the massive layer of skin. One suggestion is that it
served as a courtship display and attractant to crocodiles of the opposite
sex, like the ornamental feathers of a peacock. Some experts have suggested
that the shield helped regulate head and body temperature in a tropical
habitat. Another guess is that it served as armor to protect the predator
when it consumed prey that fought back with large teeth and claws. An
entertaining aspect of paleontology is that anyone can speculate about
the purpose of an extinct animal's morphological features. Since the
creature is long gone, no one is likely to prove your suggestion wrong.
Besides having an unusual covering on the snout, the shieldcroc specimen
is notable for being the earliest known direct ancestor of modern crocodilians
(which include alligators and caimans). Within the Mesozoic era, the
Jurassic geologic period was followed by the Cretaceous, approximately
145 to 65 million years ago. During that time, crocodilians expanded
into a wide diversity of terrestrial, freshwater, and saltwater habitats.
Today's 23 species of modern crocodilians live primarily in freshwater
systems, occasionally making excursions onto land. Saltwater crocodiles
of Australia and New Guinea are noted for oceangoing trips but their
primary residence is in estuarine or freshwater habitats.
Today's crocodilians are all top-of-the-food-chain carnivores, eating
other reptiles, mammals, birds, amphibians, and fishes. The now-extinct
crocodilians of the late Mesozoic period had much greater species diversity,
and this was reflected in their broad array of food preferences. Some
were meat or fish eaters; others were insectivorous, even herbivorous.
Does a plant-eating crocodile sound improbable? Consider that a six-foot-long
flower-eating iguana lizard is a huge, herbivorous reptile similar in
shape to a crocodile. How an animal (or plant) evolves depends not only
on its ancestry but also on who the survivors were.
must have been formidable creatures, and capturing one would have given
today's hunters of American alligators something worth bragging about.
In the United States we have two native crocodilians--American crocodiles
native to southern Florida and alligators found in much of the Southeast.
Fortunately, neither species indulges in the antisocial behavior of
eating people for a living. American crocodiles typically behave like
alligators, which are usually shy and inoffensive.
Australia, saltwater crocodiles roam the rivers and coastal marshes
near where people live. These crocodiles are very different from American
alligators with regard to their interactions with humans--they will
unhesitatingly attack and eat people. If you want to experience something
akin to what an encounter with large scary reptiles might have been
like when dinosaurs were on the wane and shieldcrocs possibly held the
franchise on ferocious reptile behavior, I suggest a trip to northern
Australia. Saltwater crocodiles are the reptile world's equivalent of
great white sharks or Bengal tigers. Their maximum size is enormous.
Not as big as a shieldcroc, but more than 20 feet long. I have seen
a 16-foot-long crocodile and have no doubt that it could easily kill
and swallow a full-grown man. If that sort of adventure doesn't appeal
to you, then you are probably glad to know that shieldcrocs no longer
inhabit the earth.
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