The entelodont family was named in 1883 by the famous Richard Lydekker. Many types
had been discovered and named even before this. Even the great legends of
paleontology like Edward Drinker Cope and Joseph Leidy had discovered and named
a few of these creatures. Often they were known from fossil teeth and jaws. We
have other, more tantalizing clues in the fossil record too. Some fossil sites
in the western United States show actual evidence of an entelodont on the hunt.
The entelodont genus in question is Archaeotherium. It was an animal the size
of a cow, and dominated this area roughly 33 million years ago.
Archaeotherium is one of the best-known entelodonts and the one that has been studied most
often. It was the largest predator of the White River fauna. This fauna existed
from the Late Eocene to the Late Oligocene, a time when the rainforests that
covered the Western Hemisphere were beginning to die out. They were replaced by
a mixed vegetation of plains mixed with dry woodlands and smaller forests.
The White River fauna is diverse and long-enduring, having existed for millions of
years. It was thus constantly changing as the landscape became more open and
mammals took up to a running lifestyle after the thick jungles began to shrink
back. Many of these early runners were smaller than their current descendants.
These include the first grazing horses, tiny early camels and a family of
sheep-like animals called oreodonts. The latter group were the commonest
Oligocene animals in North America. They were early relatives of today’s
ruminants like cattle, sheep and goats.
One of the best places to find Oligocene White River fossils is Badlands National
Park in South Dakota. Fossils of several grazing and browsing mammals have been
found with the bite marks of Archaeotherium on them. Whether they are hunted or
scavenged is questionable but we can see that this terminator pig was certainly
consuming other animals on quite a regular basis. These marks have been found
on almost everything here, from creatures as small as primitive horses and
camels to the large hornless rhinos of the area.
Fossilized footprints in Toadstool Geologic Park record an Archaeotherium that had been
actively stalking a hornless rhino called Subhyracodon. However, even the rhino
had been defenseless against the bone-crushing bite of the entelodont. The
footprints show that the Archaeotherium had been ambushing the rhino in a wet,
swampy area. When the time came, the pursuer attacked and the rhino changed
direction with the monstrous entelodont hot on its heels. Archaeotherium and
other entelodonts did not rely on advanced brainpower. Despite their huge
heads, their brains were no larger than an orange. None of the herbivores had
very large brains either, and the predators themselves were those that hunted
The entelodonts managed to survive the changing world of the Oligocene. The
continent became much drier and cooler and the forests began to shrink even
further as the Miocene set in. Grasslands began to spread with the spread of
ruminants, or the mammals that chew cud. The oreodonts, early representatives
of this group, were replaced by more well-adapted creatures. The Miocene is
widely considered as the heyday of the mammals, lasting from 25 to 5 million
years ago. Many mammal families were taking on their modern forms, with larger
sizes in early horses and camels, and relatives of deer, giraffes and pronghorn
being among the newer arrivals. Three-meter tall chalicotheres and running
rhinos were the largest herbivores here. Still the last of the entelodonts
persisted with incredible stubbornness, becoming one of the largest predatory
land mammals in history.
Its name was Daeodon, and once again this beast was the ruler of western North
America. This gigantic animal was close to 1.8 meters tall, as big as a bison.
It was similar to other entelodonts except that it was obviously far more
powerful given its huge size. There were still plenty of differences from
Archaeotherium. For one, its cheek flanges were much smaller and blunter than
those of its relatives. The fossils of this animal were first found in the John
Day Fossil Beds in Oregon, while a spectacular complete skeleton was found in
Agate Springs Quarry in Nebraska. Daeodon’s fossils are around 20 million old.
These sites and the majority of Early Miocene North American formations
preserve a world where the old system was dying out and a new fauna was
beginning to dominate the continent. Daeodon was the last part of this older
order to pull through, coming into existence at the beginning of the period and
dying out before its end.
Daeodon was the ruler of this new world for quite some time but its days were still
numbered. It was still the small-brained ambush predator that all entelodonts
were and large size could not help it in this department. Some of the most
common of these new carnivores were the bear-dogs. They were Eurasian migrants
that used the Bering Land Bridge between North America and Russia to cross over
to the new world. These were a large group of predators related to the
ancestors of perhaps both bears and dogs.
The smaller ones like Cynelos were somewhat like wolves in their habits. The
largest, like the savage Amphicyon were almost like fast-running bears.
Bear-dogs dominated the Northern Hemisphere for millions of years, from the
earliest Oligocene to the end of the Miocene. They had the flexible backs of
cats and they hunted by ambush. Despite their size they were still not as huge
as Daeodon. Where they lacked in bulk, they more than made up for it in terms
of intelligence. Amphicyon was as big as any modern bear and so its smaller
size would have granted it greater speed over its rival entelodonts. Under such
pressure, the old order waned fast and the last of the entelodonts found itself
outcompeted by these fast, fierce predators.
For a while, this was what North America’s wildlife was like. Huge doglike
predators roamed far and wide while the herbivores around them kept evolving,
becoming more and more like their modern counterparts. The likes of Daeodon
though, would never come back. While the entelodonts lasted they were the most
terrifying and powerful predators of the evolving landscapes in the Northern
Hemisphere. All that remains of them today are their fossilized bones, and
mathematical estimations of their raw power.