Giant Mammal and Megafauna Pictures and Profiles
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The Giant Mammals of the Cenozoic Era
During the latter part of the Cenozoic Era—from about 50 million
years ago to the end of the last Ice Age—prehistoric mammals were
significantly bigger (and stranger) than their modern counterparts. On
the following slides, you'll find pictures and detailed profiles of over
80 different giant mammals and megafauna that ruled the earth after the dinosaurs went extinct, ranging from Aepycamelus to the Woolly Rhino.
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Aepycamelus
Name:
Aepycamelus (Greek for "tall camel"); pronounced AY-peeh-CAM-ell-us
Habitat:
Plains of North America
Historical Epoch:
Middle-Late Miocene (15-5 million years ago)
Size and Weight:
About 10 feet high at the shoulder and 1,000-2,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Large size; long, giraffe-like legs and neck
Right off the bat, there are two odd things about Aepycamelus: first, this megafauna camel looked more like a giraffe, with its long legs and slender neck, and second, it lived in Miocene
North America (not a place one normally associates with camels,
whatever the era!) Befitting its giraffe-like appearance, Aepycamelus
spent most of its time nibbling the leaves off high trees, and since it
lived well before the earliest humans no one ever attempted to take it
for a ride (which would have been a difficult proposition, in any case).
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Agriarctos
Name:
Agriarctos (Greek for "dirt bear"); pronounced AG-ree-ARK-tose
Habitat:
Woodlands of western Europe
Historical Epoch:
Late Miocene (11 million years ago)
Size and Weight:
About four feet long and 100 pounds
Diet:
Omnivorous
Distinguishing Characteristics:
Small size; quadrupedal posture; dark fur with white spots
About Agriarctos
As rare as it is today, the Giant Panda's family tree stretches all
the way back to the Miocene epoch, over 10 million years ago. Exhibit A
is the newly discovered Agriarctos, a pint-sized (only 100 pounds or so)
prehistoric bear that spent much of its time scampering up trees,
either to harvest nuts and fruit or to evade the attention of large
predators. Based on its limited fossil remains, paleontologists believe
Agriarctos possessed a coat of dark fur with light patches around its
eyes, belly and tail--a stark contrast to the Giant Panda, on which
these two colors are distributed much more evenly.
(For the record, Agriarctos is no longer the earliest Giant Panda
precursor; that honor belongs to Kretzoiarctos, which lived about a
million years before. The latest development is that the type species of
Agriarctos, A. beatrix, has been "synonymized" with Kretzoiarctos, meaning that most paleontologists no longer consider it a valid genus.)
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Agriotherium
Name:
Agriotherium (Greek for "sour beast"); pronounced AG-ree-oh-THEE-ree-um
Habitat:
Plains of North America, Eurasia and Africa
Historical Period:
Late Miocene-Early Pleistocene (10-2 million years ago)
Size and Weight:
Up to eight feet long and 1,000-1,500 pounds
Diet:
Omnivorous
Distinguishing Characteristics:
Large size; long legs; dog-like build
One of the largest bears that ever lived, the half-ton Agriotherium achieved a remarkably wide distribution during the Miocene and Pliocene
epochs, reaching as far as North America, Eurasia and Africa (there are
no modern bears indigenous to Africa today). Agriotherium was
characterized by its relatively long legs (which gave it a vaguely
dog-like appearance) and blunt snout studded with massive, bone-crushing
teeth--a hint that this prehistoric bear may have scavenged the
already-dead carcasses of other megafauna mammals
rather than hunting down live prey. Like modern bears, Agriotherium
supplemented its diet with fish, fruit, vegetables, and pretty much any
other kind of digestible food it happened across.
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Andrewsarchus
The jaws of Andrewsarchus—the largest terrestrial mammalian predator
that ever lived—were so huge and powerful that, conceivably, this Eocene
meat-eater might have been able to bite through the shells of giant
turtles, See 10 Facts About Andrewsarchus
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Arsinoitherium
Name:
Arsinoitherium (Greek for "Arsenoe's beast," after a mythical queen of Egypt); pronounced ARE-sih-noy-THEE-re-um
Habitat:
Plains of northern Africa
Historical Epoch:
Late Eocene-Early Oligocene (35-30 million years ago)
Size and Weight:
About 10 feet long and one ton
Diet:
Plants
Distinguishing Characteristics:
Rhinoceros-like trunk; two conical horns on head; quadrupedal posture; primitive teeth
Although it wasn't directly ancestral to the modern rhinoceros,
Arsinoitherium (the name refers to the mythical Egyptian Queen Arsenoe)
cut a very rhino-like profile, with its stumpy legs, squat trunk and
herbivorous diet. However, what really set this prehistoric mammal apart
from the other megafauna of the Eocene
epoch were the two large, conical, pointed horns jutting out from the
middle of its forehead, which were likely a sexually selected
characteristic rather than anything meant to intimidate predators
(meaning that males with bigger, pointier horns had a better chance of
pairing up with females during mating season). Arsinoitherium was also
equipped with 44 flat, stumpy teeth in its jaws, which were well-adapted
to chewing the extra-tough plants of its Egyptian habitat circa 30
million years ago.
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Astrapotherium
Name:
Astrapotherium (Greek for "lightning beast"); pronounced AS-trap-oh-THEE-ree-um
Habitat:
Plains of South America
Historical Epoch:
Early-Middle Miocene (23-15 million years ago)
Size and Weight:
About nine feet long and 500-1,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Long, squat trunk; long neck and head
During the Miocene
epoch, South America was cut off from the rest of the world's
continents, resulting in the evolution of a bizarre array of mammalian megafauna (much like Australia today). Astrapotherium was a typical example: this hooved ungulate (a distant relative of horses)
looked like a cross between an elephant, a tapir and a rhinoceros, with
a short, prehensile trunk and powerful tusks. The nostrils of
Astrapotherium were also set unusually high, a hint that this
prehistoric herbivore may have pursued a partly amphibious lifestyle,
like a modern hippopotamus. (By the way, Astropotherium's name--Greek
for "lightning beast"--seems particularly inappropriate for what must
have been a slow, ponderous plant eater.)
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The Auroch
The Auroch is one of the few prehistoric animals to be commemorated
in ancient cave paintings. As you might have guessed, this ancestor of
modern cattle figured on the dinner menu of early humans, who helped
drive the Auroch into extinction. See an in-depth profile of the Auroch
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Brontotherium
Befitting its similarity to the duck-billed dinosaurs that preceded
it by tens of millions of years, the giant hooved mammal Brontotherium
had an unusually small brain for its size—which may have made it ripe
picking for the predators of Eocene North America. See an in-depth profile of Brontotherium
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Camelops
Name:
Camelops (Greek for "camel face"); pronounced CAM-ell-ops
Habitat:
Plains of North America
Historical Epoch:
Pleistocene-Modern (2 million-10,000 years ago)
Size and Weight:
About seven feet tall and 500-1,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Large size; thick trunk with long neck
Camelops is famous for two reasons: first, this was the last
prehistoric camel to be indigenous to North America (until it was hunted
to extinction by human settlers about 10,000 years ago), and second, a
fossil specimen was unearthed in 2007 during excavations for a Wal-Mart
store in Arizona (hence this individual's informal name, the Wal-Mart
Camel). Lest you think Wal-Mart might appropriate Camelops as its
official greeter, fear not: the remains of this megafauna mammal were donated for further study to nearby Arizona State University.
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The Cave Bear
The Cave Bear (Ursus spelaeus) was one of the most common
megafauna mammals of Pleistocene Europe. An astonishing number of Cave
Bear fossils have been discovered, and some caves in Europe have yielded
literally thousands of bones. See 10 Facts About the Cave Bear
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The Cave Goat
Name:
Myotragus (Greek for "mouse goat"); pronounced MY-oh-TRAY-gus; also known as the Cave Goat
Habitat:
Mediterranean islands of Majorca and Minorca
Historical Epoch:
Pleistocene-Modern (2 million-5,000 years ago)
Size and Weight:
About four feet long and 100 pounds
Diet:
Plants
Distinguishing Characteristics:
Relatively small size; forward-facing eyes; possible cold-blooded metabolism
You might think it strange that a creature as ordinary and
inoffensive as a prehistoric goat would make headlines around the world,
but Myotragus merits the attention: according to one analysis, this
smallish "Cave Goat" adapted to the sparse food of its island habitat by
evolving a cold-blooded metabolism, similar to that of reptiles. (In
fact, the authors of the paper compared fossilized Myotragus bones to
those of contemporary reptiles, and found similar growth patterns.)
As you might expect, not everyone subscribes to the theory that
Myotragus had a reptile-like metabolism (which would make it the first
mammal in history to have ever evolved this bizarre trait). More likely,
this was simply a slow, stubby, ponderous, small-brained Pleistocene
herbivore that had the luxury of not having to defend itself against
natural predators. An important clue is the fact that Myotragus had
forward-facing eyes; similar grazers have wide-set eyes, the better to
detect carnivores approaching from all directions.
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The Cave Hyena
Like other opportunistic predators of the Pleistocene epoch, Cave
Hyenas preyed on early humans and hominids, and they weren't shy about
stealing the hard-earned kill of packs of Neanderthals and other large
predators. See an in-depth profile of the Cave Hyena
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The Cave Lion
The Cave Lion came by its name not because it lived in caves, but
because intact skeletons have been discovered in Cave Bear habitats
(Cave Lions preyed on hibernating Cave Bears, which must have seemed
like a good idea until their victims woke up!) See an in-depth profile of the Cave Lion
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Chalicotherium
Why would a one-ton megafauna mammal be named after a pebble, rather
than a boulder? Simple: the "chalico" part of its name refers to
Chalicotherium's pebble-like teeth, which it used to grind down tough
vegetation. See an in-depth profile of Chalicotherium
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Chamitataxus
Name
Chamitataxus (Greek for "taxon from Chamita"); pronounced CAM-ee-tah-TAX-us
Habitat
Woodlands of North America
Historical Epoch
Late Miocene (6 million years ago)
Size and Weight
About one foot long and one pound
Diet
Insects and small animals
Distinguishing Characteristics
Slender build; good smell and hearing
Chamitataxus runs counter to the general rule that every modern
mammal had a plus-sized ancestor lurking millions of years back in its
family tree. Somewhat disappointingly, this badger of the Miocene
epoch was about the same size as its descendants of today, and it seems
to have behaved in much the same way, locating small animals with its
excellent smell and hearing and killing them with a quick bite to the
neck. Perhaps the small proportions of Chamitataxus can be explained by
the fact that it coexisted with Taxidea, the American Badger, which
still annoys homeowners in the present day.
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Coryphodon
Perhaps because efficient predators were in short supply during the
early Eocene epoch, Coryphodon was a slow, lumbering beast, with an
unusually small brain that beckons comparison with those of its dinosaur
predecessors. See an in-depth profile of Coryphodon
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Daeodon (Dinohyus)
The Miocene pig Daeodon (formerly known as Dinohyus) was roughly the
size and weight of a modern rhinoceros, with a broad, flat, warthog-like
face complete with "warts" (actually fleshy wattles supported by bone).
See an in-depth profile of Daeodon
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Deinogalerix
Name:
Deinogalerix (Greek for "terrible polecat"); pronounced DIE-no-GAL-eh-rix
Habitat:
Woodlands of western Europe
Historical Epoch:
Late Miocene (10-5 million years ago)
Size and Weight:
About two feet long and 10 pounds
Diet:
Probably insects and carrion
Distinguishing Characteristics:
Large size; rat-like tail and feet
It's true that most mammals of the Miocene
epoch grew to plus sizes, but Deinogalerix—perhaps it should be better
known as the dino-hedgehog—had an added incentive: this prehistoric
mammal seems to have been restricted to a few isolated islands off the
southern coast of Europe, a sure evolutionary recipe for gigantism.
About the size of a modern tabby cat, Deinogalerix probably made its
living by feeding on insects and the carcasses of dead animals. Although
it was directly ancestral to modern hedgehogs, for all intents and
purposes Deinogalerix looked like a giant rat, with its naked tail and
feet, narrow snout, and (one imagines) overall peskiness.
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Desmostylus
Name:
Desmostylus (Greek for "chain pillar"); pronounced DEZ-moe-STYLE-us
Habitat:
Shorelines of the northern Pacific
Historical Epoch:
Miocene (23-5 million years ago)
Size and Weight:
About six feet long and 500 pounds
Diet:
Plants
Distinguishing Characteristics:
Hippo-like body; shovel-shaped tusks in lower jaw
If you happened across Desmostylus 10 or 15 million years ago, you
might be forgiven for mistaking it for a direct ancestor of either
hippopotamuses or elephants: this megafauna mammal had a thick, hippo-like body, and the shovel-shaped tusks jutting out of its lower jaw were reminiscent of prehistoric proboscids like Amebelodon.
The fact is, though, that this semi-aquatic creature was a true
evolutionary one-off, inhabiting its own obscure order, "Desmostylia,"
on the mammalian family tree. (The other members of this order include
the truly obscure, but amusingly named, Behemotops, Cornwallius and
Kronokotherium.) It was once believed that Desmostylus and its equally
strange relatives subsisted on seaweed, but a more likely diet now seems
to have been the wide range of marine vegetation surrounding the
northern Pacific basin.
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Doedicurus
This slow-moving prehistoric armadillo Doedicurus was not only
covered by a large, domed, armored shell, but it possessed a clubbed,
spiked tail similar to those of the ankylosaur and stegosaur dinosaurs
that preceded it by tens of millions of years. See an in-depth profile of Doedicurus
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Elasmotherium
For all its size, bulk and presumed aggressiveness, the single-horned
Elasmotherium was a relatively gentle herbivore—and one adapted to
eating grass rather than leaves or shrubs, as evidenced by its heavy,
oversized, flat teeth and lack of incisors. See an in-depth profile of Elasmotherium
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Embolotherium
Name:
Embolotherium (Greek for "battering ram beast"); pronounced EM-bo-low-THEE-ree-um
Habitat:
Plains of central Asia
Historical Epoch:
Late Eocene-Early Oligocene (35-30 million years ago)
Size and Weight:
About 15 feet long and 1-2 tons
Diet:
Plants
Distinguishing Characteristics:
Large size; broad, flat shield on snout
Embolotherium was one of the central Asian representatives of the family of large herbivorous mammals
known as brontotheres ("thunder beasts"), which were ancient (and
distant) cousins of the modern rhinoceros. Of all the brontotheres
(which also included Brontotherium),
Embolotherium had the most distinctive "horn," which actually looked
more like a broad, flat shield sticking up from the end of its snout. As
with all such animal accoutrements, this odd structure may have been
used for display and/or to produce sounds, and it was doubtless a
sexually selected characteristic as well (meaning males with more
prominent nose ornaments mated with more females).
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Eobasileus
Name:
Eobasileus (Greek for "dawn emperor"); pronounced EE-oh-bass-ih-LAY-us
Habitat:
Plains of North America
Historical Epoch:
Middle-Late Eocene (40-35 million years ago)
Size and Weight:
About 12 feet long and one ton
Diet:
Plants
Distinguishing Characteristics:
Rhino-like body; three matched horns on skull; short tusks
For all intents and purposes, Eobasileus can be considered a slightly smaller version of the more famous Uintatherium, yet another prehistoric megafauna mammal
that roamed the plains of Eocene North America. Like Uintatherium,
Eobasileus cut a vaguely rhino-shaped profile, and had an exceptionally
knobby head sporting three matched pairs of blunt horns as well as short
tusks. It's still unclear how these "uintatheres" of 40 million years
ago were related to modern herbivores; all we can say for sure, and
leave it at that, is that they were very large ungulates (hooved
mammals).
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Eremotherium
Name:
Eremotherium (Greek for "solitary beast"); pronounced EH-reh-moe-THEE-ree-um
Habitat:
Plains of North and South America
Historical Epoch:
Pleistocene-Modern (2 million-10,000 years ago)
Size and Weight:
About 20 feet long and 1-2 tons
Diet:
Plants
Distinguishing Characteristics:
Large size; long, clawed hands
Yet another of the gigantic sloths that prowled the Americas during the Pleistocene epoch, Eremotherium differed from the equally huge Megatherium in that it was technically a ground, and not a tree, sloth (and thus more closely related to Megalonyx,
the North American ground sloth discovered by Thomas Jefferson).
Judging by its long and arms and huge, clawed hands, Eremotherium made
its living by mauling and eating trees; it lasted well into the last Ice
Age, only to be hunted to extinction by the early human settlers of
North and South America.
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Ernanodon
Name:
Ernanodon; pronounced er-NAN-oh-don
Habitat:
Plains of central Asia
Historical Epoch:
Late Paleocene (57 million years ago)
Size and Weight:
About two feet long and 5-10 pounds
Diet:
Insects
Distinguishing Characteristics:
Small size; long claws on front hands
Sometimes, all it takes to propel an obscure prehistoric mammal onto
the evening news is the discovery of a new, almost intact specimen. The
central Asian Ernanodon has actually been known to paleontologists for
over 30 years, but the "type fossil" was in such bad shape that few took
notice. Now, the discovery of new Ernanodon specimen in Mongolia has
cast new light on this strange mammal, which lived in the late Paleocene
epoch, less than 10 million years after the dinosaurs went extinct.
Long story short, Ernanodon was a small, digging mammal that seems to
have been ancestral to modern pangolins (which it probably resembled).
As to whether Ernanodon burrowed in search of prey, or to escape the
predation of larger mammals, that will have to await future fossil
discoveries!
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Eucladoceros
Name:
Eucladoceros (Greek for "well-branched horns"); pronounced YOU-clad-OSS-eh-russ
Habitat:
Plains of Eurasia
Historical Epoch:
Pliocene-Pleistocene (5 million-10,000 years ago)
Size and Weight:
About eight feet long and 750-1,000 pounds
Diet:
Grass
Distinguishing Characteristics:
Large size; large, ornate antlers
In most respects, Eucladoceros wasn't much different from modern deers and moose, to which this megafauna mammal
was directly ancestral. What really set Eucladoceros apart from its
modern descendants were the large, branching, multi-tined antlers
sported by the males, which were used for intra-species recognition
within the herd and also were a sexually selected characteristic (that
is, males with bigger, more ornate horns were more likely to impress
females). Oddly enough, the antlers of Eucladoceros don't seem to have
grown in any regular pattern, possessing a fractal, branching shape that
must have been an impressive sight during mating season.
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Eurotamandua
Name:
Eurotamandua ("European tamandua," a modern genus of anteater); pronounced YOUR-oh-tam-ANN-do-ah
Habitat:
Woodlands of western Europe
Historical Epoch:
Middle Eocene (50-40 million years ago)
Size and Weight:
About three feet long and 25 pounds
Diet:
Ants
Distinguishing Characteristics:
Large size; powerful front limbs; long, tube-like snout
In an odd reversal of the usual pattern with megafauna mammals,
Eurotamandua wasn't significantly bigger than modern anteaters; in
fact, this three-foot-long creature was considerably smaller than the
modern Giant Anteater, which can attain lengths of over six feet.
However, there's no mistaking Eurotamandua's diet, which can be inferred
from its long, tubular snout, powerful, clawed front limbs (which were
used for digging up anthills), and muscular, gripping tail (which held
it in place as it settled in for a nice, long meal). What's less clear
is whether Eurotamandua was a true anteater, or a prehistoric mammal
more closely related to modern pangolins; paleontologists are still
debating the issue.
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Gagadon
If you're announcing a new genus of artiodactyl, it helps to come up
with a distinctive name, since even-toed mammals were thick on the
ground in early Eocene North America--which explains Gagadon, named after the pop superstar Lady Gaga. See an in-depth profile of Gagadon
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The Giant Beaver
Did Castoroides, the Giant Beaver, build giant dams? If it did, no
evidence has been preserved, though some enthusiasts point to a
four-foot-high dam in Ohio (which may well have been made by another
animal, or a natural process). See an in-depth profile of the Giant Beaver
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The Giant Hyena
Pachycrocuta, also known as the Giant Hyena, followed a recognizably
hyena-like lifestyle, stealing freshly killed prey from its fellow
predators of Pleistocene Africa and Eurasia and occasionally even
hunting for its own food. See an in-depth profile of the Giant Hyena
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The Giant Short-Faced Bear
With its presumed speed, the Giant Short-Faced Bear may have been
capable of running down the prehistoric horses of Pleistocene North
America, but it doesn't seem to have been built robustly enough to
tackle larger prey. See an in-depth profile of the Giant Short-Faced Bear
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Glossotherium
Name:
Glossotherium (Greek for "tongue beast"); pronounced GLOSS-oh-THEE-ree-um
Habitat:
Plains of North and South America
Historical Period:
Pleistocene-Modern (2 million-10,000 years ago)
Size and Weight:
About 13 feet long and 500-1,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Large claws on front paws; large, heavy head
Yet another of the giant megafauna mammals
that prowled the forests and plains of Pleistocene North and South
America, Glossotherium was slightly smaller than the truly gigantic Megatherium but slightly bigger than its fellow ground sloth Megalonyx
(which is famous for having been discovered by Thomas Jefferson).
Glossotherium seems to have walked on its knuckles, in order to protect
its large, sharp front claws, and it's famous for having turned up in
the La Brea Tar Pits alongside the preserved remains of Smilodon, the Saber-Tooth Tiger, which may have been one of its natural predators.
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Glyptodon
The giant armadillo Glyptodon was probably hunted to extinction by
early humans, who prized it not only for its meat but also for its roomy
carapace--there's evidence that South American settlers sheltered from
the elements under Glyptodon shells! See an in-depth profile of Glyptodon
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Hapalops
Name:
Hapalops (Greek for "gentle face"); pronounced HAP-ah-lops
Habitat:
Woodlands of South America
Historical Epoch:
Early-Middle Miocene (23-13 million years ago)
Size and Weight:
About four feet long and 50-75 pounds
Diet:
Plants
Distinguishing Characteristics:
Long, stout legs; long claws on front feet; few teeth
Giant mammals always have diminutive ancestors lurking somewhere far
down on the family tree, a rule that applies to horses, elephants and,
yes, sloths. Everyone knows about the Giant Sloth,
Megatherium, but you may not have been aware that this multi-ton beast
was related to the sheep-sized Hapalops, which lived tens of millions of
years earlier, during the Miocene
epoch. As prehistoric sloths go, Hapalops had a few odd
characteristics: the long claws on its front hands probably obliged it
to walk on its knuckles, like a gorilla, and it seems to have possessed a
slightly bigger brain than its descendants further on down the line.
The paucity of teeth in Hapalops' mouth is a clue that this mammal
subsisted on soft vegetation that didn't require much robust
chewing--maybe it needed a bigger brain to find its favorite meals!
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The Horned Gopher
The Horned Gopher (genus name Ceratogaulus) lived up to its name:
this foot-long, otherwise inoffensive gopher-like creature sported a
pair of sharp horns on its snout, the only rodent ever known to have
evolved such an elaborate head display. See an in-depth profile of the Horned Gopher
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Hyrachyus
Name:
Hyrachyus (Greek for "hyrax-like"); pronounced HI-rah-KAI-uss
Habitat:
Plains of North America
Historical Epoch:
Middle Eocene (40 million years ago)
Size and Weight:
About 3-5 feet long and 100-200 pounds
Diet:
Plants
Distinguishing Characteristics:
Moderate size; muscular upper lip
You may never have given the matter much thought, but modern-day
rhinoceroses are most closely related to tapirs--pig-like ungulates with
flexible, elephant-trunk-like upper lips (tapirs are famous for their
cameo appearance as "prehistoric" beasts in Stanley Kubrick's movie 2001: A Space Odyssey).
As far as paleontologists can tell, the 40-million-year-old Hyrachus
was ancestral to both these creatures, with rhino-like teeth and the
barest beginnings of a prehensile upper lip. Oddly enough, considering
its descendants, this megafauna mammal was named after an entirely different (and even more obscure) modern creature, the hyrax.
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Hyracodon
Name:
Hyracodon (Greek for "hyrax tooth"); pronounced hi-RACK-oh-don
Habitat:
Woodlands of North America
Historical Epoch:
Middle Oligocene (30-25 million years ago)
Size and Weight:
About five feet long and 500 pounds
Diet:
Plants
Distinguishing Characteristics:
Horse-like build; three-toed feet; large head
Although Hyracodon looked a lot like a prehistoric horse--which were thick on the ground in Oligocene
North America--an analysis of this creature's legs shows that it wasn't
a particularly fast runner, and therefore probably spent most of its
time in sheltered woodlands rather than open plains (where it would have
been more susceptible to predation). In fact, Hyracodon is now believed
to have been the earliest megafauna mammal
on the evolutionary line leading to modern-day rhinoceroses (a journey
that included some truly enormous intermediate forms, such as the 15-ton
Indricotherium).
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Icaronycteris
Name:
Icaronycteris (Greek for "Icarus night flyer"); pronounced ICK-ah-roe-NICK-teh-riss
Habitat:
Woodlands of North America
Historical Epoch:
Early Eocene (55-50 million years ago)
Size and Weight:
About one foot long and a few ounces
Diet:
Insects
Distinguishing Characteristics:
Small size; long tail; shrew-like teeth
Probably for aerodynamic reasons, prehistoric bats weren't any bigger
(or any more dangerous) than modern bats. Icaronycteris is the earliest
bat for which we have solid fossil evidence, and even 50 million years
ago it had a full panoply of bat-like traits, including wings made of
skin and a talent for echolocation (moth scales have been found in the
stomach of one Icaronycteris specimen, and the only way to catch moths
at night is with radar!) However, this early Eocene
bat did betray some primitive characteristics, mostly involving its
tail and teeth, which were relatively undifferentiated and shrew-like
compared to the teeth of modern bats. (Oddly enough, Icaronycteris
existed in the same time and place as another prehistoric bat that
lacked the ability to echolocate, Onychonycteris.)
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Indricotherium
A gigantic ancestor of the modern rhinoceros, the 15-to-20-ton
Indricotherium possessed a fairly long neck (though nothing approaching
what you'd see on a sauropod dinosaur), as well as surprisingly thin
legs capped by three-toed feet. See an in-depth profile of Indricotherium
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Josephoartigasia
Name
Josephoartigasia; pronounced JOE-seff-oh-ART-ih-GAY-zha
Habitat
Plains of South America
Historical Epoch
Pliocene-Early Pleistocene (4-2 million years ago)
Size and Weight
About 10 feet long and one ton
Diet
Probably plants
Distinguishing Characteristics
Large size; blunt, hippo-like head with large front teeth
You think you have a mouse problem? It's a good thing you didn't live
in South America a few million years ago, when the one-ton rodent
Josephoartigasia prowled the continent's swamps and estuaries. (For the
sake of comparison, Josephoartigasia's closest living relative, the
Pacarana of Bolivia, "only" weighs about 30 to 40 pounds, and the
next-biggest prehistoric rodent, Phoberomys, was about 500 pounds
lighter.) Since it's represented in the fossil record by a single skull,
there's still a lot paleontologists don't know about the every life of
Josephoartigasia; we can only guess at its diet, which probably
consisted of soft plants (and possibly fruits), and it likely wielded
its giant front teeth either to compete for females or to deter
predators (or both).
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The Killer Pig
Entelodon has been immortalized as the "Killer Pig," even though,
like modern pigs, it ate plants as well as meat. This Oligocene mammal
was about the size of a cow, and had a noticeably pig-like face with
wart-like, bone-supported wattles on its cheeks. More about the Killer Pig
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Kretzoiarctos
Name:
Kretzoiarctos (Greek for "Kretzoi's bear"); pronounced KRET-zoy-ARK-tose
Habitat:
Woodlands of Spain
Historical Epoch:
Late Miocene (12-11 million years ago)
Size and Weight:
About four feet long and 100 pounds
Diet:
Probably omnivorous
Distinguishing Characteristics:
Moderate size; possibly panda-like fur coloring
A few years ago, paleontologists discovered what was then considered
to be the earliest ancestor of the modern Panda Bear, Agriarctos (aka
the "earth bear"). Now, further study of some Agriarctos-like fossils
unearthed in Spain has led experts to designate an even earlier genus of
Panda ancestor, Kretzoiarctos (after paleontologist Miklos Kretzoi).
Kretzoiarctos lived about a million years before Agriarctos, and it
enjoyed an omnivorous diet, feasting on the tough vegetables (and
occasional small mammals) of its western European habitat. Exactly how
did a hundred-pound, tuber-eating bear evolve into the much bigger,
bamboo-eating Giant Panda of eastern Asia? That's a question that demands further study (and further fossil discoveries)!
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Leptictidium
When various fossils of Leptictidium were unearthed in Germany a few
decades ago, paleontologists were faced with a conundrum: this small,
shrew-like mammal appeared to be completely bipedal! See an in-depth
profile of Leptictidium
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Leptomeryx
Name
Leptomeryx (Greek for "light ruminant"); pronounced LEP-toe-MEH-rix
Habitat
Plains of North America
Historical Epoch
Middle Eocene-Early Miocene (41-18 million years ago)
Size and Weight
About 3-4 feet long and 15-35 pounds
Diet
Plants
Distinguishing Characteristics
Small size; slender body
As common as it was on the North American plains tens of million of
years ago, Leptomeryx would get more press if it were easier to
classify. Outwardly, this slender artiodactyl (even-toed hooved mammal)
resembled a deer, but it was technically a ruminant, and thus had more
in common with modern cows. (Ruminants possess multi-segmented stomachs
designed to digest tough vegetable matter, and are also constantly
chewing their cud.) One interesting thing about Leptomeryx is that the
later species of this megafauna mammal had a more elaborate tooth
structure, which was probably an adaptation to their increasingly
parched ecosystem (which encouraged the growth of tougher-to-digest
plants).
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Macrauchenia
The long trunk of Macrauchenia hints that this megafauna mammal fed
on the low-lying leaves of trees, but its horse-like teeth point to a
diet of grass. One can only conclude that Macrauchenia was an
opportunistic browser and grazer, which helps to explain its
jigsaw-puzzle-like appearance. See an in-depth profile of Macrauchenia
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Megaloceros
The males of Megaloceros were distinguished by their enormous,
spreading, ornate antlers, which spanned almost 12 feet from tip to tip
and weighed just short of 100 pounds. Presumably, this prehistoric deer
had an exceptionally strong neck! See an in-depth profile of Megaloceros
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Megalonyx
Besides its one-ton bulk, Megalonyx, aso known as the Giant Ground
Sloth, was distinguished by its significantly longer front than hind
legs, a clue that it used its long front claws to rope in copious
amounts of vegetation from trees. See an in-depth profile of Megalonyx
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Megatherium
Megatherium, aka the Giant Sloth, is an interesting case study in
convergent evolution: if you ignore its thick coat of fur, this mammal
was anatomically very similar to the tall, pot-bellied, razor-clawed
breed of dinosaurs known as therizinosaurs. See an in-depth profile of Megatherium
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Megistotherium
Name:
Megistotherium (Greek for "largest beast"); pronounced meh-JISS-toe-THEE-ree-um
Habitat:
Plains of north Africa
Historical Epoch:
Early Miocene (20 million years ago)
Size and Weight:
About 12 feet long and 1,000-2,000 pounds
Diet:
Meat
Distinguishing Characteristics:
Large size; elongated skull with powerful jaws
You can get the true measure of Megistotherium by learning its last,
i.e., species name: "osteophlastes," Greek for "bone-crushing." This was
the biggest of all the creodonts, the carnivorous mammals that preceded
modern wolves, cats and hyenas, weighing close to a ton and with a
long, massive, powerfully jawed head. As big as it was, though, it's
possible that Megistotherium was unusually slow and clumsy, a hint that
it may have scavenged already-dead carcasses (like a hyena) rather than
actively hunting down prey (like a wolf). The only megafauna carnivore to rival it in size was Andrewsarchus, which may or may not have been substantially bigger, depending on whose reconstruction you believe!
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Menoceras
Name:
Menoceras (Greek for "crescent horn"); pronounced meh-NOSS-seh-ross
Habitat:
Plains of North America
Historical Epoch:
Early-Middle Miocene (30-20 million years ago)
Size and Weight:
About 4-5 feet long and 300-500 pounds
Diet:
Plants
Distinguishing Characteristics:
Small size; horns on males
As prehistoric rhinoceroses go, Menoceras didn't cut an especially
impressive profile, especially compared to such gigantic, weirdly
proportioned members of the breed as the 20-ton Indricotherium
(which appeared on the scene much later). The true importance of the
slender, boar-sized Menoceras is that it was the first ancient rhino to
evolve horns, a small pair on the snouts of males (a sure sign that
these horns were a sexually selected characteristic, and not meant as a
form of defense). The discovery of numerous Menoceras bones in various
places in the United States (including Nebraska, Florida, California and
New Jersey) is evidence that this megafauna mammal roamed the American plains in wide-ranging herds.
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Merycoidodon
Name:
Merycoidodon (Greek for "ruminant-like teeth"); pronounced MEH-rih-COY-doe-don
Habitat:
Plains of North America
Historical Epoch:
Oligocene (33-23 million years ago)
Size and Weight:
About five feet long and 200-300 pounds
Diet:
Plants
Distinguishing Characteristics:
Short legs; horse-like head with primitive teeth
Merycoidodon is one of those prehistoric herbivores that's hard to
get a good grasp on, since it doesn't have any analogous counterparts
alive today. This megafauna mammal
is technically classified as a "tylopod," a subfamily of artiodactyls
(even-toed ungulates) related to both pigs and cattle, and today
represented only by modern camels. However you choose to classify it,
Merycoidodon was one of the most successful grazing mammals of the Oligocene
epoch, represented as it is by thousands of fossils (an indication that
Merycoidodon roamed the North American plains in vast herds).
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Mesonyx
Name:
Mesonyx (Greek for "middle claw"); pronounced MAY-so-nix
Habitat:
Plains of North America
Historical Epoch:
Early-Middle Eocene (55-45 million years ago)
Size and Weight:
About five feet long and 50-75 pounds
Diet:
Meat
Distinguishing Characteristics:
Wolf-like appearance; narrow snout with sharp teeth
If you saw a picture of Mesonyx, you might be forgiven for thinking that it was ancestral to modern wolves and dogs: this Eocene
mammal had a slender, quadrupedal build, with canine-like paws and a
narrow snout (probably tipped by a wet, black nose). However, Mesonyx
appeared way too early in evolutionary history to be directly related to
dogs; rather, paleontologists speculate that it may have lain near the
root of the evolutionary branch that led to whales (note its similarity to the land-dwelling whale ancestor Pakicetus). Mesonyx also played an important part in the discovery of another, bigger Eocene carnivore, the gigantic Andrewsarchus; this central Asian megafauna predator was reconstructed from a single, partial skull based on its presumed relationship to Mesonyx.
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Metamynodon
Name:
Metamynodon (Greek for "beyond Mynodon"); pronounced META-ah-MINE-oh-don
Habitat:
Swamps and rivers of North America
Historical Epoch:
Late Eocene-Early Oligocene (35-30 million years ago)
Size and Weight:
About 13 feet long and 2-3 tons
Diet:
Plants
Distinguishing Characteristics:
Large size; high-set eyes; four-toed front feet
If you've never quite understood the difference between rhinoceroses
and hippopotamuses, you're bound to be confused by Metamynodon, which
was technically a prehistoric rhinoceros but looked much, much more like
an ancient hippo. In a classic example of convergent evolution—the
tendency for creatures that occupy the same ecosystems to evolve the
same traits and behaviors—Metamynodon possessed a bulbous, hippo-like
body and high-set eyes (the better for scanning its surroundings while
it was submerged in water), and lacked the horn characteristic of modern
rhinos. Its immediate successor was the Miocene Teleoceras, which also
looked like a hippo but at least possessed the smallest hint of a nasal
horn.
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Metridiochoerus
Name
Metridiochoerus (Greek for "frightful pig"); pronounced meh-TRID-ee-oh-CARE-us
Habitat
Plains of Africa
Historical Epoch
Late Pliocene-Pleistocene (3 million-one million years ago)
Size and Weight
About five feet long and 200 pounds
Diet
Probably omnivorous
Distinguishing Characteristics
Moderate size; four tusks in upper jaw
Although its name is Greek for "frightful pig," and it's sometimes
called the Giant Warthog, Metridiocheorus was a true runt among the
multi-ton mammalian megafauna of Pleistocene
Africa. The fact is that, at 200 pounds or so, this prehistoric porker
was only slightly bigger than the still-extant African Warthog, albeit
equipped with more dangerous-looking tusks. The fact that the African
Warthog survived into the modern age, while the Giant Warthog went
extinct, may have had something to with the latter's inability to
survive times of scarcity (after all, a smaller mammal can endure famine
for longer stretches than a larger one).
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Moropus
Name:
Moropus (Greek for "stupid foot"); pronounced MORE-oh-pus
Habitat:
Plains of North America
Historical Epoch:
Early-Middle Miocene (23-15 million years ago)
Size and Weight:
About 10 feet long and 1,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Horse-like snout; three-toed front feet; longer front than hind limbs
Although the name Moropus ("stupid foot") is striking in translation,
this prehistoric mammal might have been better served by its original
moniker, Macrotherium ("giant beast")--which would at least drive home
its relationship to the other "-therium" megafauna of the Miocene epoch, especially its close relative Chalicotherium.
Essentially, Moroopus was a slightly bigger version of Chalicotherium,
both of these mammals characterized by their long front legs, horse-like
snouts and herbivorous diets. Unlike Chalicotherium, though, Moropus
seems to have walked "properly" on its three-clawed front feet, rather
than on its knuckles, like a gorilla.
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Mylodon
Name:
Mylodon (Greek for "peaceful tooth"); pronounced MY-low-don
Habitat:
Plains of South America
Historical Epoch:
Pleistocene-Modern (2 million-10,000 years ago)
Size and Weight:
About 10 feet long and 500 pounds
Diet:
Plants
Distinguishing Characteristics:
Relatively small size; thick hide; sharp claws
Compared to its fellow giant sloths like the three-ton Megatherium
and Eremotherium, Mylodon was the runt of the litter, "only" measuring
about 10 feet from head to tail and weighing about 500 pounds. Perhaps
because it was relatively small, and thus a more likely target for
predators, this prehistoric megafauna mammal
had an unusually tough pelt reinforced by tough "osteoderms," and it
was also equipped with sharp claws (which probably weren't used for
defense, but to root out tough vegetable matter). Interestingly, the
scattered pelt and dung fragments of Mylodon have been so well preserved
that paleontologists once believed this prehistoric sloth never went
extinct, and was still living in the wilds of South America (a premise
that was soon proven incorrect).
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Nesodon
Name:
Nesodon (Greek for "island tooth"); pronounced NAY-so-don
Habitat:
Woodlands of South America
Historical Epoch:
Late Oligocene-Middle Miocene (29-16 million years ago)
Size and Weight:
About 5 to 10 feet long and 200 to 1,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Large head; stocky trunk
Named in the mid-19th century by the famous paleontologist Richard Owen,
Nesodon was only assigned as a "toxodont"—and thus a close relative of
the better-known Toxodon—in 1988. Somewhat confusingly, this South
American megafauna mammal
comprised three separate species, ranging from sheep-sized to
rhinoceros-sized, all of them looking vaguely like a cross between a
rhino and a hippopotamus. Like its closest relatives, Nesodon is
technically categorized as a "notoungulate," a distinctive breed of
hooved mammals that have left no direct living descendants.
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Nuralagus
The Pliocene rabbit Nuralagus weighed over five times as much as any
species of rabbit or hare living today; the single fossil specimen
points to an individual of at least 25 pounds! See an in-depth profile of Nuralagus
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Obdurodon
The ancient monotreme Obdurodon was about the same size as its modern
playtpus relatives, but its bill was comparably broad and flat and
(here's the main difference) studded with teeth, which adult platypuses
lack. See an in-depth profile of Obdurodon
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Onychonycteris
Name:
Onychonycteris (Greek for "clawed bat"); pronounced OH-nick-oh-NICK-teh-riss
Habitat:
Woodlands of North America
Historical Period:
Early Eocene (55-50 million years ago)
Size and Weight:
A few inches long and a few ounces
Diet:
Insects
Distinguishing Characteristics:
Five-clawed hands; primitive inner ear structure
Onychonycteris, the "clawed bat," is a case study in the unexpected
twists and turns of evolution: this prehistoric bat existed alongside
Icaronycteris, another flying mammal of early Eocene
North America, yet it differed from its winged relative in several
important respects. Whereas the inner ears of Icaronycteris show the
beginnings of "echolating" structures (meaning this bat must have been
capable of night hunting), the ears of Onychonycteris were much more
primitive. Assuming that Onychonycteris has precedence in the fossil
record, this would mean that the earliest bats developed the ability to
fly before they developed the ability to echolocate, though not all
paleontologists are convinced.
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Palaeocastor
Name:
Palaeocastor (Greek for "ancient beaver"); pronounced PAL-ay-oh-cass-tore
Habitat:
Woodlands of North America
Historical Epoch:
Late Oligocene (25 million years ago)
Size and Weight:
About one foot long and a few pounds
Diet:
Plants
Distinguishing Characteristics:
Small size; strong front teeth
The 200-pound Castoroides
may be the best-known prehistoric beaver, but if was far from the
first: that honor probably belongs to the much smaller Palaeocastor, a
foot-long rodent that eschewed elaborate dams for even more elaborate,
eight-foot-deep burrows. Oddly enough, the preserved remnants of these
burrows—narrow, twisty holes known in the American west as "Devil's
Corkscrews"—were discovered long before Palaeocastor itself, and it took
some convincing on the part of scientists before people accepted that a
creature as small as Palaeocastor could be so industrious. Even more
impressively, Palaeocastor seems to have dug out its burrows not with
its hands, like a mole, but with its oversized front teeth!
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Palaeochiropteryx
Name:
Palaeochiropteryx (Greek for "ancient hand wing"); pronounced PAL-ay-oh-kih-ROP-teh-rix
Habitat:
Woodlands of western Europe
Historical Epoch:
Early Eocene (50 million years ago)
Size and Weight:
About three inches long and one ounce
Diet:
Insects
Distinguishing Characteristics:
Primitive wings; distinctive inner-ear structure
At some point during the early Eocene epoch--and probably well before, as far back as the late Cretaceous
period--the first mouse-sized mammals evolved the ability to fly,
inaugurating the evolutionary line leading to modern bats. The tiny (no
more than three inches long and one ounce) Palaeochiropteryx already
possessed the beginnings of the bat-like inner-ear structure necessary
for echolocation, and its stubby wings would have allowed it to flutter
at low altitudes over the forest floors of western Europe. Not
surprisingly, Palaeochiropteryx seems to have been closely related to
its North American contemporary, the early Eocene Icaronycteris.
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Palaeolagus
Name:
Palaeolagus (Greek for "ancient rabbit"); pronounced PAL-ay-OLL-ah-gus
Habitat:
Plains and woodlands of North America
Historical Epoch:
Oligocene (33-23 million years ago)
Size and Weight:
About one foot long and a few pounds
Diet:
Grass
Distinguishing Characteristics:
Short feet; long tail; rabbit-like build
Disappointingly, the ancient rabbit Palaeolagus wasn't monster-sized,
like so many prehistoric ancestors of existing mammals (for sake of
contrast, witness the Giant Beaver,
Castoroides, which weighed as much as a full-grown human). Except for
its slightly shorter hind feet (a clue that it didn't hop like modern
rabbits), two pairs of upper incisors (compared to one for modern
rabbits) and slightly longer tail, Palaeolagus looked remarkably like
its modern descendants, complete with long bunny ears. Very few complete
fossils of Palaeolagus have been found; as you might imagine, this tiny
mammal was so often preyed on by Oligocene carnivores that it has survived down to the present day only in bits and pieces.
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Paleoparadoxia
Name:
Paleoparadoxia (Greek for "ancient puzzle"); pronounced PAL-ee-oh-PAH-ra-DOCK-see-ah
Habitat:
Shorelines of the northern Pacific
Historical Epoch:
Miocene (20-10 million years ago)
Size and Weight:
About 10 feet long and 1,000-2,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Short, inward-curving legs; bulky body; horse-like head
Like its close relative, Desmostylus, Paleoparadoxia represented an
obscure offshoot of semi-aquatic mammals that died off about 10 million
years ago and left no living descendants (though they may be distantly
related to dugongs and manatees). Named by a bemused paleontologist
after its odd mix of features, Paleoparadoxia (Greek for "ancient
puzzle") had a large, horse-like head, a squat, walrus-like trunk, and
splayed, inward-curving legs more reminiscent of a prehistoric crocodile than a megafauna mammal. Two complete skeletons of this creature are known, one from the Pacific coast of North America and another from Japan.
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Pelorovis
Name:
Pelorovis (Greek for "monstrous sheep"); pronounced PELL-oh-ROVE-iss
Habitat:
Plains of Africa
Historical Epoch:
Pleistocene-Modern (2 million-5,000 years ago)
Size and Weight:
About 10 feet long and one ton
Diet:
Grass
Distinguishing Characteristics:
Large size; large, upward-curving horns
Despite its fanciful name—which is Greek for "monstrous
sheep"—Pelorovis wasn't a sheep at all, but a gigantic artiodactyl
(even-toed ungulate) closely related to the modern water buffalo. This
central African mammal looked like a gigantic bull, the most notable
difference being the huge (about six feet long from base to tip), paired
horns on top of its massive head. As you might expect for a tasty bit
of mammalian megafauna
that shared the African plains with early humans, specimens of
Pelorovis have been found bearing the imprints of primitive stone
weapons.
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Peltephilus
Name:
Peltephilus (Greek for "armor lover"); pronounced PELL-teh-FIE-luss
Habitat:
Plains of South America
Historical Epoch:
Late Oligocene-Early Miocene (25-20 million years ago)
Size and Weight:
About five feet long and 150-200 pounds
Diet:
Unknown; possibly omnivorous
Distinguishing Characteristics:
Armor plating along back; two horns on snout
One of the more comical-looking megafauna mammals of prehistoric times, Peltephilus looked like a giant badger pretending to be a cross between an Ankylosaurus
and a rhinoceros. This five-foot-long armadillo sported some
impressive-looking, flexible armor (which would have allowed it to curl
up into a big ball when threatened), as well as two largish horns on its
snout, which were undoubtedly a sexually selected characteristic (i.e.,
Peltephilus males with bigger horns got to mate with more females). As
big as it was, though, Peltephilus was no match for giant armadillo
descendants like Glyptodon and Doedicurus that succeeded it by a few million years.
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Phenacodus
Name:
Phenacodus (Greek for "obvious teeth"); pronounced fee-NACK-oh-duss
Habitat:
Plains of North America
Historical Epoch:
Early-Middle Eocene (55-45 million years ago)
Size and Weight:
About five feet long and 50-75 pounds
Diet:
Grass
Distinguishing Characteristics:
Long, straight legs; long tail; narrow snout
Phenacodus was one of the "plain vanilla" mammals of the early Eocene
epoch, a medium-sized, vaguely deer- or horse-like herbivore that
evolved a mere 10 million years after the dinosaurs had gone extinct.
Its importance lies in the fact that it seems to have occupied the root
of the ungulate family tree; Phenaocodus (or a close relative) may have
been the hoofed mammal from which later perissodactyls (odd-toed
ungulates) and artiodactyls (even-toed ungulates) both evolved. This
creature's name, Greek for "obvious teeth," derives from its, well,
obvious teeth, which were well-suited to grinding up the tough
vegetation of its North American habitat.
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Platygonus
Name:
Platygonus; pronounced PLATT-ee-GO-nuss
Habitat:
Plains of North America
Historical Epoch:
Late Miocene-Modern (10 million-10,000 years ago)
Size and Weight:
About three feet long and 100 pounds
Diet:
Plants
Distinguishing Characteristics:
Long legs; pig-like snout
Peccaries are vicious, omnivorous, pig-like herd animals that live
mostly in South and Central America; Platygonus was one of their oldest
ancestors, a relatively long-legged member of the breed that may
occasionally have ventured beyond the forests of its North American
habitat and onto the open plains. Unlike modern peccaries, Platygonus
seems to have been a strict herbivore, using its dangerous-looking tusks
only to intimidate predators or other members of the herd (and possibly
to help it dig up tasty vegetables). This megafauna mammal also had an unusually advanced digestive system similar to that of ruminants (i.e., cows, goats and sheep).
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Poebrotherium
Name:
Poebrotherium (Greek for "grass-eating beast"); pronounced POE-ee-bro-THEE-ree-um
Habitat:
Plains of North America
Historical Epoch:
Oligocene (33-23 million years ago)
Size and Weight:
About three feet tall and 75-100 pounds
Diet:
Plants
Distinguishing Characteristics:
Small size; llama-like head
It's a little-known fact that the first camels evolved in North
America--and that these pioneering ruminants (i.e., cud-chewing mammals)
only later spread to northern Africa and the Middle East, where most
modern camels are found today. Named in the middle 19th century by the
famous paleontologist Joseph Leidy,
Poebrotherium is one of the earliest camels yet identified in the
fossil record, a long-legged, sheep-sized herbivore with a distinctly
llama-like head. At this stage in camel evolution, about 35 to 25
million years ago, characteristic features like fatty humps and knobby
legs had yet to appear; in fact, if you didn't know Poebrotherium was a
camel, you might assume this megafauna mammal was a prehistoric deer.
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Potamotherium
Name:
Potamotherium (Greek for "river beast"); pronounced POT-ah-moe-THEE-ree-um
Habitat:
Rivers of Europe and North America
Historical Epoch:
Miocene (23-5 million years ago)
Size and Weight:
About five feet long and 20-30 pounds
Diet:
Fish
Distinguishing Characteristics:
Slender body; short legs
When its fossils were first discovered, way back in 1833, no one was
quite sure what to make of Potamotherium, though the preponderance of
the evidence pointed to its being a prehistoric weasel (a logical
conclusion, given this megafauna mammal's
sleek, weasel-like body). However, further studies have relocated
Potamotherium on the evolutionary tree as a distant ancestor of modern
pinnipeds, a family of marine mammals that includes seals and walruses.
The recent discovery of Puijila, the "walking seal," has sealed the
deal, so to speak: these two mammals of the Miocene epoch were clearly closely related to each other.
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Protoceras
Name:
Protoceras (Greek for "first horn"); pronounced PRO-toe-SEH-rass
Habitat:
Plains of North America
Historical Epoch:
Late Oligocene-Early Miocene (25-20 million years ago)
Size and Weight:
About 3-4 feet long and 100-200 pounds
Diet:
Plants
Distinguishing Characteristics:
Four-toed feet; three pairs of short horns on head
If you came across Protoceras and its "protoceratid" relatives 20
million years ago, you might be forgiven for thinking that these
megafauna mammals were prehistoric deer. Like so many ancient
artiodactyls (even-toed ungulates), though, Protoceras and its ilk have
proven difficult to classify; their closest living relatives are most
likely camels rather than elks or pronghorns. Whatever its
classification, Protoceras was one of the earliest members of this
distinctive group of megafauna mammals,
with four-toed feet (later protoceratids only had two toes) and, on the
males, three sets of paired, stubby horns running from the top of the
head down to the snout.
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Puijila
The 25-million-year-old Puijila didn't look much like the ultimate
ancestor of modern seals, sea lions and walruses--in the same way that
"walking whales" like Ambulocetus didn't much resemble their giant
marine descendants. See an in-depth profile of Puijila
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Pyrotherium
Name:
Pyrotherium (Greek for "fire beast"); pronounced PIE-roe-THEE-ree-um
Habitat:
Woodlands of South America
Historical Epoch:
Early Oligocene (34-30 million years ago)
Size and Weight:
About 10 feet long and 500-1,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Long, narrow skull; tusks; elephant-like trunk
You'd think a dramatic name like Pyrotherium—Greek for "fire
beast"—would be bestowed on a dragon-like prehistoric reptile, but no
such luck. Pyrotherium was actually a medium-sized, vaguely
elephant-like megafauna mammal
that prowled the woodlands of South America about 30 million years ago,
its tusks and prehensile snout pointing to a classic pattern of
convergent evolution (in other words, Pyrotherium lived like an elephant,
so it evolved to look like an elephant as well). Why "fire beast?" This
is because this herbivore's remains were discovered in beds of ancient
volcanic ash.
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Samotherium
Name:
Samotherium (Greek for "Samos beast"); pronounced SAY-moe-THEE-ree-um
Habitat:
Plains of Eurasia and Africa
Historical Epoch:
Late Miocene-Early Pliocene (10-5 million years ago)
Size and Weight:
About 10 feet tall and half a ton
Diet:
Plants
Distinguishing Characteristics:
Short neck; two ossicones on head
You can tell just by looking at it that Samotherium enjoyed a lifestyle very different from that of modern giraffes: This megafauna mammal
possessed a relatively short neck and a cow-like muzzle, indicating
that it grazed on the low-lying grass of late Miocene Africa and Eurasia
rather than nibbling the high leaves of trees. Still, there's no
mistaking Samotherium's kinship with modern giraffes, as evidenced by
the pair of ossicones (horn-like protuberances) on its head and its
long, slender legs.
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Sarkastodon
Name:
Sarkastodon (Greek for "flesh-tearing tooth"); pronounced sar-CASS-toe-don
Habitat:
Plains of central Asia
Historical Epoch:
Late Eocene (35 million years ago)
Size and Weight:
About 10 feet long and 500-1,000 pounds
Diet:
Meat
Distinguishing Characteristics:
Bear-like build; long, fluffy tail
Once you get past its name--which has nothing to do with the word
"sarcastic"--Sarkastodon looms in importance as a large creodont of the
late Eocene epoch (the creodonts were a prehistoric group of carnivorous megafauna mammals
that preceded modern wolves, hyenas and big cats). In a typical example
of convergent evolution, Sarkastodon looked a lot like a modern grizzly
bear (if you make allowances for its long, fluffy tail), and it
probably lived a lot like a grizzly bear as well, feeding
opportunistically on fish, plants and other animals. Also, Sarkastodon's
large, heavy teeth were especially well adapted to cracking bones,
either of live prey or already-dead carcasses.
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The Shrub-Ox
Name
Shrub-Ox; genus name Euceratherium (pronounced YOU-see-rah-THEE-ree-um)
Habitat
Plains of North America
Historical Epoch
Pleistocene-Modern (2 million-10,000 years ago)
Size and Weight
About six feet long and 1,000-2,000 pounds
Diet
Trees and shrubs
Distinguishing Characteristics
Long horns; shaggy coat of fur
A true bovid--the family of cloven-hoofed ruminants whose modern
members include cows, gazelles and impalas--the Shrub-Ox was notable for
grazing not on grass, but on low-lying trees and shrubs
(paleontologists can determine this by examining this megafauna mammal's
coprolites, or fossilized poop). Oddly enough, the Shrub-Ox inhabited
North America for tens of thousands of years before the arrival of the
continent's most famous bovid, the American Bison, which migrated from Eurasia via the Bering land bridge. Like other megafauna mammals in its general size range, Euceratherium went extinct shortly after the last Ice Age, about 10,000 years ago.
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Sinonyx
Name:
Sinonyx (Greek for "Chinese claw"); pronounced sie-NON-nix
Habitat:
Plains of eastern Asia
Historical Epoch:
Late Paleocene (60-55 million years ago)
Size and Weight:
About five feet long and 100 pounds
Diet:
Meat
Distinguishing Characteristics:
Moderate size; large, long head; hooves on feet
Although it looked--and behaved--uncannily like a prehistoric dog,
Sinonyx actually belonged to a family of carnivorous mammals, the
mesonychids, that went extinct about 35 million years ago (other famous
mesonychids included Mesonyx and the gigantic, one-ton Andrewsarchus,
the largest terrestrial mammalian predator that ever lived). The
moderately sized, tiny-brained Sinonyx prowled the plains and seashores
of late Paleocene Asia a mere 10 million years after the dinosaurs went
extinct, an example of how quickly the tiny mammals of the Mesozoic Era
evolved during the ensuing Cenozoic to occupy vacant ecological niches.
One thing that set Sinonyx apart from the true prehistoric ancestors
of dogs and wolves (which arrived on the scene millions of years later)
is that it possessed small hooves on its feet, and was ancestral not to
modern mammalian carnivores, but to even-toed ungulates like deer, sheep
and giraffes. Until recently, paleontologists even speculated that
Sinonyx may even have been ancestral to the first prehistoric whales
(and thus a close relative of early cetacean genera like Pakicetus and
Ambulocetus), though it now seems that mesonychids were distant cousins
to the whales, a few times removed, rather than their direct
progenitors.
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Sivatherium
Like many megafauna mammals of the Pleistocene epoch, Sivatherium was
hunted to extinction by early humans; crude pictures of this
prehistoric giraffe have been found preserved on rocks in the Saharan
Desert, dating to tens of thousands of years ago. See an in-depth profile of Sivatherium
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The Stag Moose
Like other Pleistocene mammals of North America, the Stag Moose may
have been hunted to extinction by early humans, but it also may have
succumbed to climate change at the end of the last Ice Age and the loss
of its natural pasture. See an in-depth profile of the Stag Moose
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Steller's Sea Cow
In 1741, a population of a thousand giant sea cows was studied by the
early naturalist Georg Wilhelm Steller, who remarked on this megafauna
mammal's tame disposition, undersized head on an oversized body, and
exclusive diet of seaweed. See an in-depth profile of Steller's Sea Cow
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Stephanorhinus
The remains of the prehistoric rhinoceros Stephanorhinus have been
found in a startling number of countries, ranging from France, Spain,
Russia, Greece, China, and Korea to (possibly) Israel and Lebanon. See an in-depth profile of Stephanorhinus
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Syndyoceras
Name:
Syndyoceras (Greek for "together horn"); pronounced SIN-dee-OSS-eh-russ
Habitat:
Plains of North America
Historical Epoch:
Late Oligocene-Early Miocene (25-20 million years ago)
Size and Weight:
About five feet long and 200-300 pounds
Diet:
Plants
Distinguishing Characteristics:
Squat body; two sets of horns
Although it looked (and probably behaved) like a modern deer, Syndyoceras was only a remote relative: true, this megafauna mammal
was an artiodactyl (even-toed ungulate), but it belonged to an obscure
sub-family of this breed, the protoceratids, the only living descendants
of which are camels. Syndyoceras males boasted some unusual head
ornamentation: a pair of large, sharp, cattle-like horns behind the
eyes, and a smaller pair, in the shape of a V, on top of the snout.
(These horns also existed on females, but in drastically reduced
proportions.) One distinctly un-deer-like characteristic of Syndyoceras
was its large, tusk-like canine teeth, which it probably used while
rooting for vegetation.
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Synthetoceras
Name:
Synthetoceras (Greek for "combined horn"); pronounced SIN-theh-toe-SEH-rass
Habitat:
Plains of North America
Historical Epoch:
Late Miocene (10-5 million years ago)
Size and Weight:
About seven feet long and 500-750 pounds
Diet:
Plants
Distinguishing Characteristics:
Large size; elongated horn on narrow snout
Synthetoceras was the latest, and largest, member of the obscure
family of artiodactyls (even-toed ungulates) known as protoceratids; it
lived a few million years after Protoceras and Syndyoceras and was at
least double their size. The males of this deer-like animal (which was
actually more closely related to modern camels) boasted one of nature's
most improbable head ornaments, a single, foot-long horn that branched
off on the end into a small V shape (this was in addition to a more
normal-looking pair of horns behind the eyes). Like modern deer,
Synthetoceras seems to have lived in large herds, where the males
maintained dominance (and competed for females) according to the size
and impressiveness of their horns.
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Teleoceras
Name:
Teleoceras (Greek for "long, horned one"); pronounced TELL-ee-OSS-eh-russ
Habitat:
Plains of North America
Historical Epoch:
Late Miocene (5 million years ago)
Size and Weight:
About 13 feet long and 2-3 tons
Diet:
Plants
Distinguishing Characteristics:
Long, hippo-like trunk; small horn on snout
One of the best-known megafauna mammals of Miocene
North America, hundreds of Teleoceras fossils have been unearthed at
Nebraska's Ashfall Fossil Beds, otherwise known as "Rhino Pompeii."
Teleoceras was technically a prehistoric rhinoceros, albeit one with
distinctively hippo-like characteristics: its long, squat body and
stumpy legs were well-adapted to a partially aquatic lifestyle, and it
even had hippo-like teeth. However, the small, almost insignificant horn
on the front of Teleoceras' snout points to its true rhinoceros roots.
(The immediate predecessor of Teleoceras, Metamynodon, was even more
hippo-like, spending most of its time in the water.)
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Thalassocnus
Name:
Thalassocnus (Greek for "sea sloth"); pronounced THA-la-SOCK-nuss
Habitat:
Shorelines of South America
Historical Epoch:
Late Miocene-Pliocene (10-2 million years ago)
Size and Weight:
About six feet long and 300-500 pounds
Diet:
Aquatic plants
Distinguishing Characteristics:
Long front claws; downward-curving snout
When most people think of prehistoric sloths, they picture huge, land-dwelling beasts like Megatherium (the Giant Sloth) and Megalonyx (the Giant Ground Sloth). But the Pliocene
epoch also witnessed its share of weirdly adapted, "one-off" sloths,
the prime example being Thalassocnus, which dived for food off the coast
of northwestern South America (the interior of that part of the
continent consisting mostly of desert). Thalassocnus used its long,
claw-tipped hands both to reap underwater plants and anchor itself to
the sea floor while it fed, and its downward-curving head may have been
tipped by a slightly prehensile snout, like that of a modern dugong.
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Titanotylopus
Name:
Titanotylopus (Greek for "giant knobbed foot"); pronounced tie-TAN-oh-TIE-low-pus
Habitat:
Plains of North America and Eurasia
Historical Epoch:
Pleistocene (3 million-300,000 years ago)
Size and Weight:
About 13 feet long and 1,000-2,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Large size; long, slender legs; single hump
The name Titanotylopus has precedence among paleontologists, but the
now-discarded Gigantocamelus makes more sense: essentially,
Titanotylopus was the "dino-camel" of the Pleistocene epoch, and was one of the biggest megafauna mammals
of North America and Eurasia (yes, camels were once indigenous to North
America!) Befitting the "dino" part of its nickname, Titanotylopus had
an unusually small brain for its size, and its upper canines were larger
than those of modern camels (but still not anything approaching
saber-tooth status). This one-ton mammal also had broad, flat feet
well-adapted to walking on rough terrain, hence the translation of its
Greek name, "giant knobbed foot."
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Toxodon
Name:
Toxodon (Greek for "bow tooth"); pronounced TOX-oh-don
Habitat:
Plains of South America
Historical Epoch:
Pleistocene-Modern (3 million-10,000 years ago)
Size and Weight:
About nine feet long and 1,000 pounds
Diet:
Grass
Distinguishing Characteristics:
Short legs and neck; large head; short, flexible trunk
Toxodon was what paleontologists call a "notoungulate," a megafauna mammal closely related to the ungulates (hoofed mammals) of the Pliocene and Pleistocene
epochs but not quite in the same ballpark. Thanks to the wonders of
convergent evolution, this herbivore evolved to look very much like a
modern rhinoceros, with stubby legs, a short neck, and teeth well
adapted to eating tough grass (it may also have been equipped with a
short, elephant-like proboscis at the end of its snout). Many Toxodon
remains have been found in close proximity to primitive arrowheads, a
sure sign that this slow, lumbering beast was hunted to extinction by
early humans.
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Trigonias
Name:
Trigonias (Greek for "three-pointed jaw"); pronounced try-GO-nee-uss
Habitat:
Plains of North America and western Europe
Historical Epoch:
Late Eocene-Early Oligocene (35-30 million years ago)
Size and Weight:
About eight feet long and 1,000 pounds
Diet:
Plants
Distinguishing Characteristics:
Five-toed feet; lack of nasal horn
Some prehistoric rhinoceroses looked more like their modern
counterparts than others: whereas you might have a hard time locating Indricotherium or Metamynodon on the rhino family tree, the same difficulty doesn't apply to Trigonias, which (if you glanced at this megafauna mammal
without your glasses on) would have cut a very rhino-like profile. The
difference is that Trigonias had five toes on its feet, rather than
three as in most other prehistoric rhinos, and it lacked even the barest
hint of a nasal horn. Trigonias lived in North America and western
Europe, the ancestral home of rhinos before they relocated farther east
after the Miocene epoch.
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Uintatherium
Uintatherium didn't excel in the intelligence department, with its
unusually small brain compared to the rest of its bulky body. How this
megafauna mammal managed to survive for so long, until it vanished
without a trace about 40 million years ago, is a bit of a mystery. See an in-depth profile of Uintatherium
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The Woolly Rhino
Coelodonta, aka the Woolly Rhino, was very similar to modern
rhinoceroses--that is, if you overlook its shaggy coat of fur and its
odd, paired horns, including a big, upward-curving one on the tip of its
snout and a smaller pair set further up, nearer its eyes. See an in-depth profile of the Woolly Rhino
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