Eohippus
Eohippus
was a small, plant-eating mammal that lived approximately 55 million
years ago. Scientists have determined this animal was the
horses first ancestor. Often referred to as the dawn horse,
Eohippus stood about 15 inches high, and was about the size of a fox.
In fact, the dawn horse closely resembled a dog-like creature, as it
lacked the straight back and long face of modern horses. The
Eohippus had four toes on its front foot (one of these was
non-functional), and three on its hind foot. Each toe ended in
a separate hoof. The part of the foot which bore the animals
weight was covered with a tough pad, much like a dogs.
Scientists have determined from fossilized teeth that Eohippus was more
of a
browser than a grazer which means it ate more like a rabbit than a
horse. But, like todays horse, the Eohippus depended on its
speed to evade predators.
Nature began replacing Eohippus with a more horse-like animal, the
Mesohippus
or middle horse, about 35
million years ago. Twenty-six million years ago Merychippus
(cud-chewing horse)
emerged. It had three toes on each foot, but the strong,
large-hoofed center toe bore all the animals weight. Animals
resembling todays horse appeared about 3 million years ago.
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Woolly
mammoth
Mammoths
are
members of an extinct genus of elephants. Woolly mammoths were a
specialized type of mammoth with long, reddish brown hair, which
protected them from the severe cold of the Ice Age
(2,000,000-10,000 years ago).
Mammoths were more closely related to elephants than were mastodons.
Measuring 14 feet high at the shoulder, the woolly mammoth
was a huge,
lumbering animal. Its tusks, which curved up and crossed in front of
its trunk, could measure up to 13 feet in length. Three inches of fat
under the skin provided further insulation, and there was a large hump
of fat on its back. The mammoths skull was high and dome-like, and its
ears were smaller than an elephants.
Mammoths first appeared in Africa 4 million years ago, and they reached
North America about 1.5 million years ago. Their fossils are among the
most common in the world. Remarkably preserved 30,000-year-old mammoths
have been found in Siberia. Prehistoric man pictured mammoths in his
cave art. In Europe, realistic depictions of entire herds of mammoths
have been found. Evidence exists that prehistoric human settlers of
North America hunted these huge animals. Mammoths became extinct at the
end of the Ice Age. |
Mastodon
Mastodons
were animals very much like modern elephants. The fossil
record shows that mastodons first appeared in northern Africa about 40
million years ago. From there they spread all over Europe,
Asia, and the rest of Africa. Approximately 14 million years
ago, mastodons arrived in the New World.
Mastodons
were related to another extinct, elephant-like species, the
four-tuskers. Both of these creatures were shorter and
stockier than modern elephants. Like four-tuskers, early types
of mastodons had tusks on both their lower and upper jaw, but many
later examples of the species no longer had this trait. Some
types of mastodons and four-tuskers had prominent lower tusks which
were very flat. These animals are called
shovel-tuskers. All mastodons were covered with reddish brown
hair, and had teeth that were much smaller and more primitive than
those of elephants.
By 10,000 years ago, at the end of the Pleistocene
Epoch, most mastodons had
disappeared. However, evidence indicates that the mastodon
existed in North America after the Pleistocene which means they would
have co-existed with historic Native American groups. Mankind
was probably a factor in the mastodons extinction, especially in North
America.
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Saber-tooth
cat
The
saber-tooth
cat of prehistoric times is classified in a subfamily of the cat family
(Felidae)
called Machairodontinae.
Saber-tooth cats were named
for their large upper canine teeth. These teeth were curved like
sabers, and could be up to eight inches long! The saber-tooth cats had
very strong necks and skulls, their lower canines were relatively small
in size, and their mouths could be opened to a 90 degree angle. All of
these features suggest the saber-tooth cat used its canine teeth for
stabbing and slashing its prey.
About 2 million years ago, during the Pleistocene Epoch, the most
famous of the saber-tooth cats, the Smilodon,
appeared. This animal
represented the peak of saber-tooth evolution. It was approximately the
same size as a tiger, but stockier and with shorter limbs. Smilodon
roamed all over North and South America hunting large plant-eaters such
as mammoths. Many Smilodon bones have been preserved in the tar pits of
Rancho La Brea in Los Angeles, California.
The saber-tooth cats became extinct approximately 10,000 years ago.
During that time the last glaciers retreated north. The changing
climate, the subsequent changes in plants, and the success of man were
probably responsible for the demise of the saber-tooth cat. |