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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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Deinonuchus
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1992-09-03
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Deinonychus
TIME: Early Cretaceous
LOCALITY: North America (Montana)
SIZE: 10-13 ft/3-4 m long
The discovery of Deinonychus in 1964 in
the claystones of Montana is one of the most
exciting finds in the recent history of
paleontology. Well-preserved skeletons reveal
a dinosaur built for the chase and the
kill--a fast, agile, intelligent
predator.Deinonychus had the lightweight body
characteristic of the ceratosaurs, from which
it probably evolved. It was, on average, 10
ft/3 m long, stood about 6 ft/1.8 m tall, and
weighed some 150 lbs/68 kg. The large head
was equipped with many meat-shearing teeth,
with serrated edges, which were curved
backward to allow great chunks of flesh to be
torn from the prey. The arms were quite long
for a theropod (though still much shorter
than the legs) and hung from sturdy shoulder
girdles. Each hand had 3 grasping fingers
with long, strongly curved claws.The legs
were slender, with long shin bones and 4
clawed toes on each foot. The first toe was
tiny and nonfunctional, as in most of the
later theropods; the third and fourth toes
carried the whole weight of the body.But it
was the remarkable adaptation of the second
toe that gave Deinonychus its most offensive
weapon--and its name, which means "terrible
claw." The second toe on each foot had a
large, sickle-shaped claw, 5 in/13 cm long.
This would have been used like a dagger, to
slash through a victim's flesh as Deinonychus
stood on one leg and kicked with its free
foot.When Deinonychus ran, the sickle-clawed
toes were flicked back and held clear of the
ground. The body was held horizontally and
balanced by the long, outstretched tail. This
was kept rigid by bundles of bony rods that
grew out from the vertebrae themselves, and
formed a supporting framework to stiffen the
tail along most of its length. When
Deinonychus was standing on one foot and
attacking with the other, balance was
essential and a tail like a ramrod would have
made the pose easier to hold. The big brain
(evident from the size of the skull's brain
cavity) would have coordinated a finely tuned
nervous system to control such complex
movements.One of the finds in Montana
revealed 5 complete skeletons of Deinonychus
lying by the body of a large, plant-eating
dinosaur called Tenontosaurus, which measured
some 24 ft/7.3 m long. This assemblage of
bodies was most probably brought together by
chance after death, washed down by a flood
into a hollow or river basin.But one could
perhaps reconstruct the scene that took place
some 140 million years ago. A small pack of
Deinonychus surrounded the plant-eater. Some
may have leapt on its back, and held on with
their clawed hands, while slashing through
its thick hide by repeated kicks of the
daggerlike, killing claws on their feet. The
plant-eater may have wounded or even killed
some of its attackers by lashing out with its
long, heavy tail or rearing up on hindlegs to
crash down on their bodies. But, perhaps in
the end, it succumbed and bled to death,
while the pack of carnivores waited
nearby.The active, predatory lifestyle
suggested by the anatomy of Deinonychus is
seen by some paleontologists as strong
evidence that it was an endothermic
("warm-blooded") creature, and could control
its body temperature, as do modern birds and
mammals.
Subject by: Russell Webb