Sabertoothed Cats: An Introduction


The lion-sized cat turned its back on a sunlit Pleistocene world of dry, open woodlands and padded into its den one last time.

Although hungry, it turned away from the half-eaten young mammoth carcass near the entrance and walked deeper into the comfortable darkness.

It went down the gently sloping dirt floor to a little pool of water that had collected as rainwater seeped in through cracks in the limestone walls and roof.

Some frogs hopped out of the way, but this cat did not lower its muzzle and start lapping. Instead, it lay down.

Something was wrong, the cat didn’t know what (nor do we, thousands of years later). Maybe a nap would help.

The cat closed its eyes, resting its head on its paws as all cats will when sleeping, and it slowly drifted off into sweet oblivion, never to stir again.


Not too long afterwards, before scavengers could disturb the body, sediments poured in, perhaps from a flood outside during a storm. Mud filled the little pool, gently flowed around and over the cat’s body, and even preserved the mammoth carcasses and other objects in the cave.

Then the entrance collapsed, sealing this tomb for thousands of years.

But rainwater continued to percolate through the limestone bedrock around the cave and a sinkhole gradually formed in the roof. When that collapsed, it opened up a 30-foot near-vertical shaft, down which some late 19th/early 20th-century Texans eventually climbed to discover bones.

Just so many bones.

The cat wasn’t found, I think, until 1949, when the owner of this cave — Albert Friesenhahn — invited some paleontologists in.

To them, the cave was a wonderland. It was filled with fossils of more than 30 major groups of mammals, reptiles, and birds.

Homotherium.
(Image: Sergiodlarosa via Wikimedia, CC BY-SA 3.0)

And the cat!

They had finally found a complete specimen of the “other” Ice Age sabertoothed cat: Homotherium.

This was a very different animal from Smilodon, the long-toothed La Brea sabercat that we all know and love.

Homotherium

Smilodon is considered a dirk-toothed sabercat.

Smilodon fatalis. (Image: Sergiodlarosa via Wikimedia, CC BY-SA 3.0)

Its upper canines are narrow and very long, with fine serrations on the edge.

Homotherium — a scimitar-toothed cat — had shorter, more coarsely serrated saberteeth.

Researchers had suspected that it was built differently, too, but up until the Friesenhahn Cave find, they only had a few fragments to study.

Now they had an entire Homotherium skeleton. Not only that, it was still intact (minus the fur and soft tissues, of course). They actually could see how Homotherium was put together!

Paleontologists rarely luck into such discoveries!

Homotherium’s most obvious differences, in addition to the teeth, were:

  • A much more slender build than Smilodon.
  • Longer legs than Smilodon or modern cats, especially the forelegs.

Later in this series we’ll look at what these differences might have meant in real life, when both of these sabercats, as well as modern cats, sometimes lived in the same ecosystem.

Researchers have had even more luck at Friesenhahn Cave, though it was a sadder find: the almost complete remains of two Homotherium cubs.

All three cats are now on display at the Texas Memorial Museum, on the campus of the University of Texas at Austin.

That’s our cat, at the top of this post, as seen at the museum.

Understanding fossil information isn’t easy

If you’re like me, you might already have constructed a story to explain how an adult sabercat and two sabercubs ended up in a cave.

“It was a dark and stormy eon . . .”
“Will you knock it off! And go get me a trowel.” (Image: N. Hawkaluk/USFS, CC BY 2.0)

It was the mother and after she died the cubs starved to death, right?

I haven’t read up on each find, but just going on the overall picture, that’s not impossible.

But with fossils, you need to consider all possibilities.

What if the cubs were born there, died, and their mother moved on? Or perhaps she was killed while out hunting.

And then later, after the cubs had passed on, this adult may have come by — sabercats probably had at least some social patterns like those of modern cats, and the cave made a good lair.

Then, while living there, it died quietly of unknown causes.

We can’t disprove that, though personally, I prefer the “family” explanation.

Paleontologists, however, can’t go by opinion.

They need to understand what really happened, so they ignore their feelings and use strict rules of logic.

This approach is difficult, not to mention contentious, but the results are often confirmed when new evidence comes to light.

So we don’t really know much about those three sabercats yet.



Here. I’m still sad about those sabercubs, too. This goes on FOREVER, and it raises an interesting question: how would the cubs handle pumpkins (and prey) with saberteeth? No one is sure of sabercat hunting and eating techniques, other than that these must have been very different from those of today’s cats.


Sabertooth variety

Even though the odds are against them, paleontologists do know lots of other things about sabertoothed cats.

The rest of this series will be about those facts. But it doesn’t start with Homotherium and Smilodon.

They were very different from modern cats, but they were also the highly specialized peak forms of a long line of sabertoothed cats and cat-like predators.

That’s all done with.

For now.

Per Switek: “Saber-Toothed Felid and Nimravid diversity . . . From Emerson, S.B., and Radinsky, L. “Functional Analysis of Sabertooth Cranial Morphology.” Paleobiology, Vol. 6, No. 3. (Summer, 1980), pp. 295-312.”

As we’re about to see, saberteeth have appeared over and over again in the fossil record.

Not continuously, though.

A line will die out for several million years and then another set of sabertoothed critters will show up.

We don’t know what evolutionary advantages saberteeth gave predators, but they were helpful or else there wouldn’t have been these long, successful runs over and over again in such an unforgiving natural world.

Typically, at the start of a sabertooth lineage, unusually long and flattened upper canine “sabers” evolve first, followed by the development of various other physical features that belong to what paleontologists call a “sabertooth complex.” (Slater and Van Valkenburgh)

Clouded leopards have the longest fangs in proportion to body size. But neither tigers nor clouded leopards have saberteeth. (Image: Dps austin via Wikimedia)

Believe it or not, today’s cats are the weirdos because they don’t have saberteeth.

Modern cats also have a primitive build, more like the Miocene’s Pseudaelurus than the most recent scimitar- and dirktoothed sabercats. (Some early “Knife-Tooths” looked like this, too, except for their unusual teeth.)

It’s as though whatever complex events caused the late Pleistocene extinctions also hit family Felidae’s reset button.

So there might be a niche available out there now for sabertoothed hypercarnivores.

We don’t know much about it, since human science developed millennia after it emptied.

But this niche will probably be filled again, perhaps millions of years from now when all that’s left of our world is stored in just one layer of the geological record.

So, how did the sabercat story begin?

Cat lovers will not be at all surprised to hear that sabertoothed predators, complete with retractable claws, shortened faces, and other cat-like features, first pounce at us from their hiding place on a shelf in the rocky archives marked “Late Eocene North America, 35-ish million years ago.”

There is no record of how they evolved, or where. They just arrived.

Just like a cat, but the Eocene was a long time ago.

Were these really cats?

People used to think so, but now it’s not clear. Some experts even suggest that (gasp!) they might have been more closely related to dogs.

But they were diverse and very successful on many continents for tens of millions of years. Their extinction in North America left a serious “cat gap” in the fossil record that wasn’t filled until Pseudaelurus crossed over on a land bridge


Featured image: Skb8721 via Wikimedia, CC BY-SA 3.0.


Sources:

Antón, M. 2014. 2013. Sabertooth. Bloomington: Indiana University Press.

Barkalow, D. 2020. Texas Stste Historical Society Association Handbook of Texas: Friesenhahn Cave. https://www.tshaonline.org/handbook/entries/friesenhahn-cave Last accessed August 27, 2020.

Barnett, R.; Barnes, I.; Phillips, M. J.; Martin, L. D.; and others. 2005. Evolution of the extinct Sabretooths and the American cheetah-like cat. Current Biology, 15(15): R589-R590.

Georgia Before People blog. 2017. The Friesenhahn Cave Fossil Site in Bexar County, Texas. https://markgelbart.wordpress.com/2017/11/14/the-friesenhahn-cave-fossil-site-in-bexar-county-texas/ Last accessed August 27, 2020.

Madurell-Malapeira, J.; Robles, J. M.; Casanovas-Vilar, I.; Abella, J.; and others. 2014. The scimitar-toothed cat Machairodus aphanistus (Carnivora: Felidae) in the Vallès-Penedès Basin (NE Iberian Peninsula). Comptes Rendus Palevol, 13(7): 569-585.

Martin, L. D. 1980. Paper 287: Functional Morphology and the Evolution of Cats. Transactions of the Nebraska Academy of Sciences and Affiliated Societies. VIII:141154

Prothero, D. R. 2006. After the Dinosaurs: The Age of Mammals. Bloomington and Indianapolis : Indiana University Press.

Slater, G. J., and Van Valkenburgh, B. 2008. Long in the tooth: evolution of sabertooth cat cranial shape. Paleobiology, 34(3): 403-419.

Switek, B. 2007. What big teeth you have . . . https://laelaps.wordpress.com/2007/10/03/what-big-teeth-you-have/ Last accessed August 27, 2020.




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