When you think of the world’s most fierce, numerous, and dominant meat-eating mammals,
you probably think of animals like the big cats, or wolves, or bears.
But long before any of those animals existed, there was another predator that prowled North
America.
And it was neither cat nor dog nor bear, but it was their distant relative.
It had the tapering snout and long tail of a dog.
But it walked on the soles of its feet and had a large body, like a bear.
Its name was Amphicyon, and it was one of the largest predatory mammals ever to walk
the Earth.
And it was just one of a very diverse group of ancient meat-eaters that ruled the northern
hemisphere for over 30 million years!
Some of these creatures were fox-like forest dwellers; others were fast, long-legged predators;
and others still, like Amphicyon, were nearly as big as polar bears.
Scientists refer to this group of extinct beasts as the Amphicyonids.
But because of their strange combination of bear-like and dog-like traits, they’re sometimes
confusingly called the beardogs.
And even though you’ve never met one of these animals, the beardogs are key to understanding
the history of an important branch of the mammal family tree.
Because, at the height of their reign, the beardogs played a pivotal role in outcompeting
another group of early dominant predators -- a group we’ve told you about before,
which has also since gone extinct.
And by getting rid of them, the beardogs paved the way for their own relatives, the carnivores
we know today.
Natural history -- like all history -- is full of overlooked characters, figures that
quietly shaped the world around them.
And if you ask me, the saga of the carnivores could never be complete without the forgotten
story of the beardogs.
Now, most of the meat-eating mammals that you know today -- like cats, dogs, and bears
-- are members of the same group, the order known as Carnivora.
And it might sound like, to be a member of this group you just have to eat meat.
But Carnivora isn’t synonymous with carnivore.
Carnivora includes animals with diverse diets, not just meat-eaters.
They range from the bamboo-chomping Giant Pandas to more omnivorous animals, like raccoons,
and even walruses!
So, a carnivore is any animal that eats other animals, but Carnivorans are a specific taxonomic
group of placental mammals.
And some of the earliest members of this group were the beardogs.
Beardogs first appear in the fossil record around 40 million years ago, during the Eocene
Epoch.
They probably originated in North America and spread into Europe before the two continents
slowly became separated.
Because of that, fossils show that two distinct lineages of beardogs wound up evolving in
isolation for millions of years.
One of the oldest-known species is actually a tiny creature from North America called
Daphoenus demilo.
It lived in the late Eocene, from Wyoming to Saskatchewan, where it survived on a diet
of plants and small animals in the dense forests that covered the continent.
And it, like all beardogs, belonged to a group of mammals known as Caniformia — the same
group that includes today’s bears and dogs, along with other familiar mammals like seals
and skunks.
Scientists think that beardogs diverged from other Caniforms early on, forming their own
branch of the mammal family tree.
Both bears and dogs evolved later, but today they are the beardogs’ closest living relatives.
And because of that, beardogs share a lot of similarities with both animals.
For example, beardogs tended to have longer, pointier snouts, like dogs and bears do.
And many beardogs were large-bodied and walked with their feet flat on the ground like bears,
but also had a long, dog-like tail.
Now, after the North American beardogs became separated from the Eurasian species, the two
groups found themselves on very different evolutionary paths.
In North America, beardogs diverged into two subfamilies, each of which played a big role
in shaping the predator-prey dynamics of the continent.
The first group appears in the fossil record about 40 million years ago, in places like
Texas and Wyoming.
Early species in this group were well-adapted for hunting in dense forests, like our friend
Daphoenus, which was probably about the size of a swift fox, or maybe as big as a coyote.
But when these first beardogs came about, there were bigger dogs on the scene.
Though they weren’t actually dogs, either.
The fiercest apex predators in Eocene North America were the Hyaenodonts -- bigger, stronger
carnivores which we’ve talked about before.
Hyaenodonts had big, powerful jaws filled with blade-like teeth.
Plus, we can tell from their heel bones that some of them could make powerful leaps, suggesting
that they probably used an ambush hunting strategy, hiding in the forest undergrowth
and tackling their prey with brute force.
Now, those first little beardogs might not have seemed like much of a threat to the hyenadonts,
but circumstances soon swung in their favor.
As the Oligocene Epoch began about 33 million years ago, North America was beginning to
go through a major cooling and drying phase.
And this opened up the landscape, turning forests into savannas.
This new, open environment spelled trouble for the specialized hunting style of the hyenadonts.
And they had another problem to deal with, too: their teeth.
Hyaenodont teeth were all adapted for ripping and tearing flesh -- great when you’re only
eating meat, but less so when your food of choice suddenly declines.
Beardogs, on the other hand, had more varied teeth.
Their front teeth were used for tearing, but their molars had different shapes and sizes.
Some could be adapted for crushing, puncturing, or holding prey, depending on what was selected
for.
And these differentiated teeth proved to be a key advantage for the beardogs.
Plus, by the start of the Oligocene, some beardog species had gotten big -- big enough
to compete with hyenadonts for the same food, while maintaining more of this adaptability.
The combination of direct competition from beardogs and an unforgiving new environment
spelled the end for the Hyaenodonts.
By about 30 million years ago, they had vanished from North America.
Soon, beardogs were on the rise.
By about 23 million years ago, several large beardogs appeared, with long legs that gave
them a more efficient stride — perfect for chasing down prey like three-toed horses and
early camelids.
But the North American beardogs were about to face much stiffer competition, and from
their own kind.
About 18 million years ago, a new threat crossed the Bering Land Bridge: even larger beardogs,
the ones that had evolved separately on Eurasia.
And over there, the beardog story had played out differently than it had in North America.
At first, the Eurasian beardogs struggled to thrive, in part because there too, they
faced competition from the hyaenodonts.
But when those bigger carnivores started to decline, the beardogs had their moment.
They quickly spread across the continent and began to fill niches that hyaenodonts had
left empty.
But rather than adapting to become sleek and long-legged like their American relatives,
Eurasian beardogs became heavier and more robust.
They were also probably more opportunistic and adaptable, hunting or scavenging on large
prey like hyenas do today.
In fact, we have direct evidence of this!
In 2006, researchers described a rhino jaw from Portugal that had bite marks matching
the teeth of a Eurasian beardog called Amphicyon giganteus.
So when the large beardogs arrived into North America, it spelled trouble for the locals.
And they were just one part of a whole wave of Eurasian carnivores that came over, shaking
up the dynamics of whole ecosystems.
These new carnivores outcompeted the North American beardogs, and by about 17 million
years ago they were extinct.
The Eurasian beardogs however, thrived in their new habitat.
They grew even larger, reaching sizes that put them among the biggest mammalian land
predators of all time.
Two species of these giants were ambush predators the size of polar bears that roamed Western
North America.
They had powerful forelimbs, massive clawed feet, and muscular jaws that could deliver
a crushing bite.
But these beardogs were about to meet the same double-threat as the hyaenodonts that
came before them -- new competition and climate change.
However this time, the situation was reversed.
Beardogs had outcompeted the hyaenodonts in part by being adaptable generalists, able
to eat more kinds of food when conditions changed.
But then those beardogs were replaced by more specialized hunters -- members of their own
family: the modern Carnivorans.
Some of these new Carnivorans included hyenas in Eurasia and borophagines in North America;
you may know them as the bone-crushing dogs.
Both of these animals could shatter bones with their teeth, something that beardogs
couldn’t do, which made them more efficient scavengers.
Plus, there was also the arrival of the cats, which began to compete for the niche of hypercarnivore,
with their razor-sharp teeth and retractable claws.
Meanwhile, bears -- actual, real bears! -- had diverged and spread, with teeth that were
adapted to a more omnivorous lifestyle.
All of these new Carnivorans were doing everything that beardogs could do, but better and in
more targeted ways.
Clearly, the days of the beardogs were numbered.
The North American beardogs had already been outcompeted by the giant Eurasian beardogs.
And with only huge ambush predators left on both continents, they couldn’t stand up
to the more specialized cats, dogs, and bears.
Some of the last species we find in the fossil record belonged to the genus of the mighty
Amphicyon.
By about 9 million years ago, beardogs on both continents were gone.
But we shouldn’t forget the role they played in shaping predator dynamics in the Age of
Mammals.
Their rise helped the carnivorans outdo their competitors, the hyenadonts.
And their fall was accompanied by the rise of the modern cats, dogs, and bears we know
today.
When the last of them vanished, the beardogs had formed a kind of bridge between old and
new: a missing puzzle piece in the 45-million-year saga of the meat-eating mammals.
Hey big thanks this month’s Eontologists: Patrick Seifert, Jake Hart, Jon Davison Ng,
and Steve!
Become an Eonite by pledging your support at patreon.com/eons!
And also high-fives for joining me in the Konstantin Haase Studio.
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