Homotherium: Saberteeth


Meet Homotherium (in 3D, possible Arctic coat), a/k/a the other sabertoothed cat.

A 19th-century taxonomist gave this fossil feline its name — homo, “same,” and therion, “beast” — for reasons that I haven’t been able to track down.

It’s a peculiar moniker, even in the multisyllabic world of paleontology.

Scientists have labeled most other sabercats with variations on old Greek or Latin words meaning “knife” and “tooth.”

There are many such names, from Machairodus to Smilodon.

Hmmm. So much for the misconception that there was a single sabertoothed cat.

Lots of different knife-tooths have prowled Africa, Eurasia, and the Americas, though perhaps not the same rainbow assortment of species that we see in today’s cone-tooths.

Wait. Cone-tooths?

Yes.

That’s how paleontologists refer to modern cats and their fossil ancestors.

Tigers have the longest fangs of any living cat. (Image: Tambako the Jaguar, CC BY-ND 2.0)

These kitties have cone-shaped fangs (upper and lower canine teeth).

Fluffy’s are rather small, but you can easily see it in a tiger.

The fangs have that shape because all cats today use their mouths to kill prey.

Fangs anchor the cat to its hapless victim. Their conical shape can handle stress loads in any direction during struggles.

But there is more to life on Earth than what we see at this moment of geologic time.

Other dental options are available for mammals: a fact that some cats have exploited successfully for a very long time.

What are saberteeth?

Saberteeth are not a new set of choppers.

They’re the same basic upper canines that Tigger and Fluffy have.

Evolution just made them longer and flattened them, like a knife, in front-to-back cross section.

Ha! Such fragile “blades” would break the first time a cat bit its victim!

Or so one would think.

However, sabertoothed cats — top predators for more than ten million years — somehow found a work-around.

We don’t know for sure what it was, though.

No eyewitness accounts of how they hunted exist, although humans and sabercats did share the Pleistocene world for a while.

In fact, no clear-cut representations of a sabertoothed cat have been found yet in Paleolithic art (Anton et al., 2009), though some ancient people in Germany used Homotherium bones to beat a drum or some other instrument (Serangeli et al.)

But the fossil record provides some clues about sabercut hunting techniques.

It shows that, along with their saberteeth, cats evolved shorter backs, longer necks, very powerful forequarters, and extremely large incisors.

Sabertoothed cats may have used these adaptations while hunting.

Turner et al., 2011, suggest that sabercats:

  • First overpowered a victim with their muscles and body weight, pinning it to the ground and holding it immobile to prevent struggles that could break the saberteeth.
  • Then they could use their long neck to precisely position their head for a soft-tissue throat bite.
  • The damage done by saberteeth would kill prey almost instantly this way. Indeed, Salesa et al. suspect that a speedy kill might be the primary advantage to saberteeth.
  • Homotherium had a very impressive arc of incisors. (Image: Animal Record, CC BY 2.0)

  • Sabercats also had huge incisors, compared to modern cats. These provided stability during the killing bite — some extra protection for those long upper fangs.
  • Afterwards, the sabercat wouldn’t eat with its sabers, of course. Like all cats, it would use its cheek teeth to slice meat and its raspy tongue and incisors to peel flesh from the bone.

This terrifying but interesting picture is called the “canine shear bite” hypothesis.

It makes sense and also explains why sabercats were built a little differently from modern cats.

So why were there two tribes of sabertoothed cat?

Dirk-tooths and scimitar-tooths

Smilodon is the best known sabercat, thanks to its dirk teeth and the many fossils it left at the La Brea pits in what is now Los Angeles, California.



The La Brea Museum makes a mean trailer!


“Dirk teeth” is the official term for those long skewers.

Homotherium is not as famous, but you might have heard of it as “the scimitar-toothed cat.”

James St. John, CC BY 2.0

Homotherium’s sabers weren’t exactly scimitars, but they were impressive and deadly: not quite as long as Smilodon’s upper fangs but broader, with serrations and what look like blood grooves.

The two sabercat types differed in other ways, too.

Dirk-toothed cats were powerfully built, like a modern-day jaguar or, in some cases, a bear.

They could have been excellent ambush hunters.

Scimitar-toothed cats were also somewhat bear-like, but they had a lighter build than the dirk-tooths and often showed adaptations for running.

Homotherium, for example, had claws that were short and, like the cheetah’s, didn’t fully retract.

This could mean that, while definitely not a cheetah-style racer, it might have spent more time in the open, pursuing prey.

But we must be careful when drawing parallels between modern and fossil cats.

Sabercats were unique in many ways, and we will never know fully what they were like.

Some Smilodon species in South America, for instance, were large enough to ambush prey by barreling into it chest first, knocking the animal down.

You don’t see lions tackling wildebeest that way!

Travis, CC BY-NC 2.0

Homotherium, the likely pursuit sabercat, was just weird.

It had long forelegs and shortened hind legs, sort of like a hyena but not as extreme. Its back did slope, though.

Are you seeing a lion-sized sabercat cantering after a fleeing prehistoric beastie?

Funny as it sounds, that’s closer to the truth than whatever dramatic reconstructions you’re likely to find online today.

But then, the Homotherini always had to be different.

How sabertoothed cats evolved

Mammals are good at bench sitting, waiting for an opportunity to join the game.

Cats are no exception.

The bobcat-sized Dawn Cat, which lived almost 30 million years ago in Europe, is quite rare in the fossil record.

Already on the field were players like Barbourofelis fricki. (Image: Ghedoghedo via Wikimedia, CC BY-SA 3.0)

Its pseudaelurine descendants about eight million years later were more numerous, as well as larger, but they weren’t yet ready to dominate Miocene ecosystems ruled by sabertoothed barbourofelids, beardogs (amphycyonids), and other scary creatures.

However, one of these felines — Pseudaelurus quadridentatus — was as big as a modern leopard and might have competed with a similar-sized barbourofelid called Sansanosmilus in Europe. (Anton)

Fossils of the two predators have been found together, anyway.

P. quadridentatus also had some subtle sabertooth features, including relatively long canines.

This makes it a likely candidate for founder of the sabercat lines.

Another pseudaelurine cat, Styriofelis lorteti, was more likely the ancestor of conical-toothed cats.

Cone-tooths apparently kept a very low profile at first, while early sabertooths became more prominent.

Even back in the day, there seem to have been two general types.

One group of sabertooths, like the cone-tooths, stayed close to the original Proailurus body plan, just adding saberteeth and robust physical features to it.

This was the Smilodontini tribe.

The Homotherini, on the other hand, were what Anton calls “precocious.”

Very early on, they developed some very advanced sabertooth features, but carried them on a very primitive frame.

One of the earliest homotherins — Machairodus (again, “knife”) — was the first cat to attain the size of a modern tiger or lion, and it had a set of scimitar-teeth that would have looked appropriate during the Pleistocene, tens of millions of years later. (Anton)

But its body and skull overall were still much like the other cats.

So Machairodus wasn’t going to wrestle prey to the ground.

Instead, its hunting technique might have been some combination of the cone-tooth and later knife-tooth styles.

As for other early homotherins, well, those names tend to shift around.

Paleontologists are very careful about this because scientific names are meant to show evolutionary relationships.

And, given the fragmentary and small amount of fossil evidence, they are still debating many aspects of sabercats and how they were related.

Let’s just say that various Eurasian and some North American members of this tribe fit into the Machairodus (11 to 9 million years ago) and Amphimachairodus (9 to about 5 million years ago) groups. (Dates are from Werdelin et al.)

These lion-sized homotherins developed more and more advanced sabertooth features over time and became apex predators in some areas.

Then they all vanished around 5 million years ago in the Miocene-Pliocene extinctions — the toll booth at the end of that Miocene bridge we imagined.

The fossil record doesn’t show what happened to them or which one was Homotherium’s daddy.

It just shows them gone and Homotherium, in all its weird glory, starting at around 4 million years ago and continuing on through the end of the Pleistocene some 10,000 years ago.

Homotherium

The oldest known Homotherium fossils are about the same age and were found in both Africa and Eurasia, so the origin of this scimitar-toothed cat isn’t clear.

What’s obvious is that Homotherium, which thrived for at least four million years, was one of the most successful cats ever!

While never as numerous as Smilodon, Homotherium was the most widespread sabercat, found across Africa and throughout Eurasia.

In the New World, its fossils have been confirmed from Venezuela all the way up into the Yukon.

Think of all the different habitats this cat adapted to!

As well, Homotherium started out in a warm Pliocene world and wasn’t the least bit fazed by global cooling and the start of ice age cycles.

It just went up to what’s now Alaska and hunted caribou, yak, and bison, with the occasional musk ox, mammoth, or horse as a side dish. (Bocherens)

Was Homotherium a group hunter out there on the mammoth steppe and elsewhere, as lions are on today’s open lands?

Some paleontologists think it’s possible. (Anton)

They point out subtle physical details that might show Homotherium up as a less than ideal solitary predator but one that could have done quite well in a pack . . . a pride . . . well, if it’s true, I think these groups should be called a horde.

It’s all very iffy, though, since social behavior leaves no direct fossil evidence.

And isotopic studies do suggest that Homotherium, at least in the Arctic, was a solitary hunter. (Bocherens)

However, they don’t show why Homotherium went extinct up there around 36,000 years ago. (Bocherens)

The end

I have left out some members of the tribe Homotherini, just to keep a tight focus and use the fewest words possible.

These other homotherins have their own stories, ones to tell in other posts.

However, if you’re keeping track, at the time of writing, Homotherini includes these groups (genera), per Haaramo:

  • Machairodus/Amphimachairodus
  • Xenosmilus
  • Lokotunjailurus
  • Homotherium

Only Homotherium made it into Plio-Pleistocene times.

When its run was over, this scimitar-toothed cat disappeared from different continents at different times.

Per Werdelin et al., Homotherium’s last known appearance in Africa was 1.4 million years ago; in Europe, about 500,000 years ago; and in North America, some 11,000 years ago at Friesenhahn Cave, which is where this post series on sabertooths started.

Let’s wait for Smilodon, next time, before we discuss possible causes of the sabercat extinctions at the end of the last ice age.


Featured image: Wim Hoppenbrouwers, CC BY-NC-ND 2.0.


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