The Sabertooths, Part 7: Extinction

Why did sabertoothed cats go extinct? Easy. More sabercats died than were born.

How did it happen? Ah, well – that’s not quite so straightforward.

It doesn’t take much to wipe out any living group: a loss of just 1% of the population per year means extinction in a century. (Oppenheimer)

And that one-percent annual loss is so very possible in any group, given all the factors involved.

In order to exist, all cats must do the following, 24/7/365:

  • Use whatever resources are around, sharing or competing for them with other cats.
  • Keep up with the changes in prey animals that can evolve rapidly and in a variety of ways.
  • Have sex and raise kittens.
  • Adapt as a population to climate changes and the resulting effects on the ecosystem.
  • Stay healthy as individuals and avoid becoming prey themselves.

This list makes our own morning commute and the typical pressures of daily modern life a little easier to face!

Sabertoothed cats did all those things for at least 12 to 14 million years. Somewhere in there are the keys to their early development, their greatest successes, and their eventual extinction.

Unfortunately, most of those details don’t fossilize; also, “prehistoric” means events that happened before written records became a thing. Paleontologists must use indirect evidence to reconstruct the world the sabercats lived in, dominated, and ultimately lost to.

Such evidence is often vague enough to allow several interpretations. That’s why there are different schools of thought on almost anything from Earth’s past.

The fact that paleontologists only have a few of the many cat fossils that are probably out there (Johnson and others) doesn’t make this research any easier.

Another reason why it isn’t easy to say what killed off the sabercats is that scientists can’t be sure, even for modern animals, which has a bigger influence on evolution – the physical environment or interactions with other living beings. (See details in Barnosky; Ezard and others)

It could have been environment, negative contacts with other life around them, or a combination of the two.

At this point, no one really knows what tipped the scales against the last sabertooths – Smilodon, Homotherium, and Xenosmilus. (Werdelin and others, Figure 2.2)

One surprising clue is the fact that today everybody has to go to Africa in order to see most of the world’s really big land mammals.

Of course they do.

But paleontologists report that, up until the end of the last Ice Age – and for at least the last 50 million years before that – big mammals were common on every known continent (Antarctica’s history is concealed by its 33-million-year-old ice cap). (Prothero, 2006; Stuart)

This was true right up until the last days of the sabertoothed cats. Now, since the great ice fronts retreated poleward, you must journey to Africa to see big game in the wild.

The disappearance of sabercats was just part of a wider event called the end-Pleistocene megafauna extinction.

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Sure, you’ve probably heard about the Ice-Age mammoths and mastodons. In North America there were other colossal animals, including beavers as large as a modern bear as well as buffalo with a 6-foot (2-meter) horn spread. (Prothero, 2006)

And there was Arctodus, a 1,500-pound (680-kilogram) bear – the largest carnivoran that has ever lived. (Prothero, 2006)

In Europe, sabertooths could hunt gigantic hippos, rhinos, and the “Irish elk” – a moose-like creature that was neither Irish nor elk – as well as other enormous prey. (Antón; Prothero, 2006)

It was the same old 50-million-year-old story, this time with a Pleistocene cast of characters.

Then, over 10 thousand years ago, the last continental ice sheet melted away and the world warmed back up into its present climate.

That was nothing unusual – this glacial-interglacial swing has been going on for some three million years. But this time, when the excess ice went away so did most of the megabeasts. (Prothero, 2006)

North and South America, as well as Australia, were the hardest hit, although extinctions were also common in northern Eurasia. (Stuart)

Yet at least half of all the other mammal groups from those days – mostly small- to medium-sized animals – are still around. (Prothero, 2006)

Sabertooths and their prey could have easily handled the ice ages by migrating toward the Equator every 120,000 years or so as great glaciers advanced. Then they would follow their usual habitat back toward the pole as ice gradually melted and the next interglacial warm period began. (Prothero, 2004)

Something must have been different at the last glacial-interglacial transition.

It does appear as though life was a struggle for big carnivores then. Tooth fracture studies at La Brea show that all of the prehistoric carnivores there broke their teeth more often than modern ones do, probably while picking bones clean. (Van Valkenburgh and Hertel)

Researchers are still working on what that might mean in the bigger picture.

In case you’re wondering, there is no clear-cut evidence that the extinction of the big Ice-Age meat-eaters happened because their prey died out. (Stuart)

The sabertooths did vanish at different times on different continents. For example, per Werdelin and others:

  • Africa: This was no refuge for sabercats. Homotherium disappeared there about 1.4 Ma.
  • Europe: Homotherium vanished 500,000 years ago.
  • North America: Homotherium went extinct some 10,000 years ago (Antón), and some of the last Smilodons sank into La Brea’s fatal embrace around 13,000 years ago.

Some experts on ancient life suggest that these extinctions coincided with the arrival of humans on each continent. (Antón)

Others, while noting that manmade extinction has indeed happened on islands, say that the intercontinental Pleistocene extinctions can’t be explained so easily. (Prothero, 2006)

New findings can change things dramatically, but right now it looks like the sabertooths and their prey were probably affected by a complex series of events related both to the arrival of modern humans and to environmental changes. (See Stuart, as well as discussion in Prothero, 2006, Chapter 8, “Death of the Megamammals”)

Those environmental changes must have been complex, and it’s possible that another, perhaps very competitive predator besides Homo sapiens may have been in the ecosystem along with the sabertoothed cats.

We know that gigantic plant-eaters died out everywhere but Africa at around the same time that the world’s ambush-and-slash sabertooth niche emptied out.

But why did sabercats first go extinct in Africa, the big-game refuge continent where megafauna still exist?

Could these guys have had something to do with it?

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The oldest known fossils of modern lions were found in Africa, and they are less than two million years ago. Then, around 500,000 years ago, lions apparently spread into Europe and parts of Asia. (Werdelin and others)

By 300,000 years ago, they were common across northern and eastern Asia. At this point, lions also crossed the Bering land bridge into North America and perhaps northern South America. (Werdelin and others)

Some experts wonder whether this had anything to do with the sabertooth extinctions. (Werdelin and others)

It isn’t clear what advantages lions might have had over sabertooths (Van Valkenburgh, 1999; Werdelin and others, but both types of cat do take big prey.

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It may take several lions to bring down prey that a single sabertooth could handle, but they can do it.

And lions once had the most extensive range of any modern cat in the wild. (Martin, 1980)

Today they can live in forests, woodlands, scrublands, grasslands, and deserts, and they have even hunted seals on the coasts. Lions eat almost any land animal they want and snack on the occasional ostrich egg or other oddity. (AZA)

Their social behavior also changes in response to local conditions (AZA), although we can’t know how this compares to the behavior of sabertoothed cats.

In tough times at the end of last Pleistocene ice age, perhaps this incredible adaptability that lions display today gave them a competitive edge over the sabercats.

Anyway, the arrival of lions seems to match the times that Homotherium and Megantereon disappeared in Africa and Homotherium vanished in Europe.

But in North America, both sabertooth tribes lingered on for tens of thousands of years after lions got there.

It’s a puzzle. Hopefully, further research, with better dating (Stuart), can show what actually happened to big animals at the end of the last ice age.


Images:
Featured image: Lake Baikal icicles, Natalia Kollegova, Pixabay. Public domain.

Mammoth (Mammuthus meridionalis), Museo Paleontologico di Montevarchi. Emiliano Burzagli. CC BY-SA 3.0.

Two lions: Davidsluka, Pixabay. Public domain.

Lions hunting. Corinata, Wikimedia. CC BY-SA 3.0.


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This series on sabertooths was originally posted at my Robin Huntingdon blog about a year ago.


The Sabertooths, Part 6: The “Other Sabertooths”

Nimravides and the Metailurini.

It sounds like a rock band, but these were once two real and very different types of long-fanged big cat:

  • Nimravides. Long-legged and at least the size of a modern lion (Antón; Hunt, 2004), this mysterious sabercat prowled North America during the late Miocene, some 10-12 million years ago.
  • The Metailurini. Part sabertooth, part “normal” cat, Metailurus and its possible tribe had a much wider range than Nimravides. Some of them were the most common Pliocene felids in Africa. (Werdelin and Dehghani)
632px-metailurus_metailurus_major_asenovgrad2

Metailurus fossils aren’t as impressive as Smilodon’s, but this cougar-like Miocene cat was tough enough to thrive alongside the big sabercats.

Very little is known about either one of them.

Of course, geoscientists don’t know much about many of the other things found while digging around in the earth, either.

On this blog, we don’t need to go into “iffiness” very often to get to Wonder. Still, it’s good to be aware that, as a noted geoscientist puts it:

“I am fond of saying that a geologist writes like a person overcoming very grave reservations. This is because no geologist can operate as an earth historian without continuously doubting such opinions—regardless of the accuracy of the observations upon which they are based. The realization of our uncertainty makes us uneasy, as does knowing that our explanations of the past are not more true, but only more plausible, than the stories told by creationists, extraterrestrialists, and other seers.” (Van Couvering)

Paleontologists still have many “grave reservations” when discussing Nimravides and the Metailurini.

Yet the basic facts are clear enough.

Both cat groups developed around the same time as the early members of the Homotheriini and Smilodontini. Then they coexisted somehow with those impressive sabercats for a reasonably long time.

Nimravides didn’t make it out of the Miocene epoch (Werdelin and others), as far as anyone knows at this point.

The last member of the Metailurini died relatively recently, during the second half of the Pleistocene. (Werdelin and Dehghani)

All of these “other” sabertooths were very successful predators, and here is their story, as far as I understand what researchers have been able to outline to date.

Nimravides

Probably the least controversial way for a layperson to introduce this sabertoothed cat is to say that it first appeared in North America 12 to 14 million years ago. (Werdelin and others)

We’re on sure ground saying it “appeared” because Nimravides definitely shows up in the fossil record. (After all, “present” is almost the only fact that anyone really knows about any cat.)

More specifically, experts report that:
“…at ~16.5-17 Ma [million years ago], the first felids enter[ed] North America from Eurasia and persist[ed] as relatively small, lynx- to leopard-sized cats until the appearance of the large lion-sized felid Nimravides…” (Hunt, 2004)

A felid is any member of the cat family, Felidae. But there’s a little more to it than that, considering how many cats have roamed this planet down through geologic time.

  • Today we live alongside the only surviving felid subgroup – Felinae, sometimes called the “conical-toothed” cats.
  • The other major subgroup – Knife-Tooths, i.e., sabercats or Machairodontinae – is extinct.

Some experts think that Nimravides may have represented yet a third subgroup. (Werdelin and others) If so, its fossils have only been found in North America, unlike the other two subgroups.

With this early Miocene immigration of Eurasian felids into North America around 17 Ma, there were now cats on every major land mass except Australia and South America.

Even before then, North America might even had some native felids, though this is only speculation. There is no solid evidence yet that this was the case. (Werdelin and others)

Anyway, as far as anyone knows now, every cat was a pseudaelurine cat – descended from Proailurus, the Dawn Cat, with “dawn” happening roughly 27 Ma. (Werdelin and others)

There must have been different species, though, because pseudaelurines evolved into at least two cat groups (three, if you count Nimravides). Paleontologists are hard at work, identifying and improving their knowledge about these founder kitties.

In life, Nimravides was indeed as big as a modern lion. It had a heftier build, though – like a tiger, with very long, muscular legs. (Antón, Figure 3.39; Hunt, 2004; Martin, 1980; Turner and Antón)

Nimravides also had saberteeth like those of Machairodus – the Old World sabertoothed cat that we met earlier in this series.

And this is where things get a little iffy again.

In the middle Miocene, around 12-14 Ma, did Nimravides:

  • Emerge first in Eurasia as Machairodus and then travel across the Bering land bridge into North America? (Antón)
  • Evolve locally from those early lynx- and leopard-sized felid immigrants to North America mentioned above by Hunt? (Werdelin and others)

No one knows for sure. (Werdelin and others)

The history of pseudaelurine cats is fairly well understood in Europe, and to a lesser degree in Asia (where there aren’t that many helpful outcrops from the right geological epoch, according to Werdelin and others), but paleontologists have yet to find Nimravides’ fossilized ancestor in North America, if it exists.

Supporters of the “Nimravides was a home boy” hypothesis offer some possible candidates – local pseudaelurine species, like P. intrepidus or P. marshi, that Nimravides resembles. (Werdelin and others)

The resemblance could mean that one of these cats evolved into Nimravides.

After all, both Intrepidus and Marshi were big, like the probable sabertooth ancestor P-Quad, a/k/a Pseudaelurus quadridentatus. (Antón)

They were also very common, accounting for three-quarters of the North American Pseudaelurus fossils that have been found thus far. (Rothwell)

But this doesn’t show whether Nimravides was related to a Machairodus species that showed up in North America around 7 Ma. (Hunt, 2004)

According to the “home boy” view, Machairodus arrived from Eurasia, and Megantereon soon followed. (Hunt, 2004)

Then, from this point until around 4.5 Ma – when Nimravides finally went extinct without leaving any descendants (Werdelin and others) – sabertooths, smaller “normal” cats like the lynx, and Nimravides coexisted in North America. (Hunt, 2004)

But some paleontologists find too many resemblances between Nimravides and Machairodus, including but not limited to the saberteeth, for it all to be a coincidence. (Antón and others)

What if P-Quad originated in Asia, back in the late Miocene, not in Europe where all of its fossils have been found so far? (Antón)

Then some individuals could have headed west into Europe and evolved into Machairodus. Others – the ancestors of Nimravides – might have traveled eastward over the Bering land bridge into North America. (Antón)

This alternative version works so well with one Nimravides species that experts have changed its name from Nimravides catocopis to Machairodus catocopis. (Antón and others; Fossilworks)

But for the other four recognized Nimravides species (Werdelin and others) . . . not so much.

Perhaps those species did descend from the early North American pseudaelurines. (Antón and others)

The scientific controversies over Nimravides will probably continue until paleontologists can establish just how the Pseudaelurus complex of cats got started, and what relationships there were among pseudaelurines in Europe, Asia, and North America. (Antón; Werdelin and others)

The Metailurini

This group of prehistoric cats roamed Africa and the nothern continents for some nine million years. (Antón)

Paleontologists have lots of “grave reservations” about them, even though the Metailurini lived much closer to our own time than Nimravides did.

First, there aren’t very many fossils available. Different experts often interpret what fragmentary evidence there is differently. (Antón)

Everybody does accept these two groups:

  • Metailurus. Ranging in size from a modern snow leopard to a large cougar, this Miocene cat apparently evolved in Eurasia. (Werdelin and others) It had moderately long, flat upper canines and was slightly more advanced than P-Quad, which it resembled. (Antón)
  • Dinofelis. This cat probably first showed up in Africa (Werdelin and Lewis) and then traveled to Eurasia and North America. (Turner and Antón) It was generally bigger than Metailurus, up to small-lion in size. (Antón) More muscular than a modern leopard, Dinofelis had the same overall proportions. Some species had moderately flat but not very long saberteeth; others had almost “normal” teeth, like today’s conical-toothed big cats. (Werdelin and Lewis)
mountain-lion-1055259_640

Metailurus is often compared to a cougar.  Experts say you can’t get an accurate reconstruction by simply adding saberteeth to a modern animal, but it’s tempting.

Just for the record, other groups associated with the Metailurini are Adelphailurus, Stenailurus, Pontosmilus, and Fortunictis. (Antón; Berta and Galiano; Werdelin and others)

However, things quickly get very technical when you start looking into those names, so let’s just move on to Metailurini controversies that are easier for laypeople like us to understand.

For example, where did these cats come from? The pseudaelurine cats apparently had disappeared before the Metailurini arrived.

Even if we just look at Metailurus and Dinofelis, nobody knows how they evolved or whether they were even closely related to each other. (Werdelin and others)

Their evolution was centered on different continents.

Too, Dinofelis was most successful during the Pliocene and Pleistocene epochs. Metailurus had its heyday in the Miocene, millions of years earlier. (Werdelin and others)

Some paleontologists suspect Metailurus may have given rise to Dinofelis. (Beaumont, quoted by Werdelin and Lewis)

Others just group these two together because they were clearly different from modern cats but didn’t have enough sabertooth features to qualify as sabercats. (Werdelin and others)

Were Metailurus and Dinofelis “Knife-Tooths” with only slight to moderate saberteeth, or were they “normal” cats (Conical-Tooths) with a tendency toward a few sabertooth characteristics? (Antón; Werdelin and others)

No one can say for sure yet.

Only one thing is clear – when it came to saberteeth, Dinofelis just couldn’t make up its mind.

The oldest and youngest Dinofelis species were definitely sabertooths (Werdelin and others), but some species in between had upper canines that weren’t much different from those you’ll see in today’s lion. (Werdelin and Lewis)

In fact, one species –Dinofelis cristata – may be the only known case where a sabertoothed cat switched over to “normal” upper canine function! (Werdelin and Lewis)

This flexibility – going from sabertooth to “normal” back to sabertooth again – leads some paleontologists to suspect that Knife-Tooths and “normal” cats competed much more directly than previously thought. (Turner and others)

We don’t know exactly how they hunted, but the sabertooths probably went after big prey (Antón; Turner and others), leaving smaller prey to the “normal” cats that were also evolving back then. (Werdelin 1989)

Theoretically, the two groups of cats could have easily shared resources because their hunting techniques were different.

But the variability in Dinofelis teeth may show that cats had more hunting options than just “sabertooth” and “normal.” (Turner and others)

This in turn could mean that “normal” cats interacted with the sabertooths in many ways, and vice versa. (Turner and others; Werdelin and others)

It’s even possible, as we will see tomorrow, that some modern cats may have been one of the culprits behind the sabertooth extinction at the end of the last ice age.

Only time and more research can tell how much each group of cats – Knife-Tooths and Cone-Tooths – affected the other group’s evolution.

Another way to look at sabertoothed cats

When you get right down to it, besides being cats, Metailurus and Dinofelis had only one physical detail in common: their lower canine teeth were unusually small. (Turner and others)

And this obscure dental detail, according to some researchers, may eventually prove beyond question that the Metailurini were Knife-Tooths.

Most of us go by the sabers when defining a sabertoothed cat.

However, as we saw last time, there is also a “sabertooth complex” of physical features that include a more powerful body and, of crucial importance to us here, a arch of very large incisors. (Antón)

Paleontologists know that, as the upper canines turn into saberteeth and the incisors get bigger, lower canine fangs usually get smaller to match the incisors.

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This reconstruction of “Barbourofelis loveorum” suggests how arcs of seriously-bite-sized incisors/lower fangs could be useful to a sabertooth.

A researcher now says that the size of lower canine teeth may be more important than sabers when it comes to sorting out sabertoothed cats.

He ran an advanced computer analysis on selected sabertooth fossil features to see what patterns showed up among the different sabertoothed cats. (Christiansen)

Surprisingly, the conventional groups of Homotheriini, Smilodontini, and Metailurini didn’t show up. (Christiansen)

Instead, Metailurus and Dinofelis, as well as Nimravides – and even Machairodus and Promegantereon! – were all linked together, mostly because their lower canines were all reduced in size. (Christiansen)

Dr. Christiansen calls these cats the Machairodontinae (Knife-Tooths). He uses the name Eumachairodontinae (True Knife-tooths) for the later saber-cats, including Megantereon, Smilodon, Amphimachairodus, Homotherium, and Xenosmilus, who sported “true” saberteeth.

amphimachairodus

Amphimachairodus giganteus.

This view is not widely accepted yet, and there are some criticisms. (See Spassov and Geraads, “Cladistic Analysis”)

We’ll have to see how this idea turns out over time.

But it’s a good example of how paleontologists are using some very advanced tools to learn more about the evolution of cats.

fossil-studier-478x346

“Here, kitty, kitty . . . “


Images:
Featured image: Metailurus major, cranial detail. Izvora. Asenovgrad Paleontological Museum. CC BY-SA 3.0.

Metailurus major. Izvora. Asenovgrad Paleontological Museum. CC BY-SA 3.0.

Puma. Skeeze. http://pixabay.com/en/mountain-lion-puma-cougar-wildlife-1055259.  Public domain.
Barbourofelis loveorum, Florida Museum of National History Fossil Hall at University of Florida: Dallas Krentzel. CC Y 2.0.

Amphimachairodus. Ghedoghedo. See page for licensing.

Fossil studier. John Day Fossil Beds National Monument staff (National Park Service). Public domain.


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

Antón, M.; Salesa, M. J.; and Siliceo, G. 2013. Machairodont adaptations and affinities of the holarctic late Miocene homotherin Machairodus (Mammalia, Carnivora, Felidae): The case of Machairoidus catocopis (Cope, 1887). Journal of Vertebrate Paleontology. 33(5):1202-1213.

Barnett, R.; Barnes, I.; Phillips, M. J.; Martin, L. D.; Harington, C. R.; Leonard, J. A.; and Cooper, A. 2005. Evolution of the extinct sabretooths and the American cheetahlike cat. Current Biology, 15(15):R589-R590.

Barnosky, A. D. 2001. Distinguishing the effects of the Red Queen and Court Jester of Miocene mammal evolution in the northern Rocky Mountains. Journal of Vertebrate Paleontology. 21(1):172-185.

Benton, M. J.; Donoghue, P. C. J.; Asher, R. J.; Friedman, M.; Near, T. J.; and Vinther, J. 2015. Constraints on the timescale of animal evolutionary history. Palaeontologia Electronica, 18.1.1FC 1-106. palaeo-electronica.org/content/fc-1.

Benton, M. J. 2009. The Red Queen and the Court Jester: Species diversity and the role of biotic and abiotic factors through time. Science. 323(5915):728-732. Abstract.

Berta, A., and Galiano, H. 1983. Megantereon hesperus from the Late Hemphillian of Florida with remarks on the phylogenetic relationships of machairodonts (Mammalia, Felidae, Machairodontinae). Journal of Paleontology. 57(5):892-899.

Best, M. G.; Barr, D. L.; Christiansen, E. H.; Gromme, S.; Deino, A. L.; and Tingey, D. G. 2009. The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks. International Geology Review. 51:7-8, 589-633.

Cain, M. L.; Bowman, W. D.; and Hacker, S. D. 2014. Ecology. Sunderland, Massachusetts: Sinauer Associates.

Chapin, C. E., Wilks, M., and McIntosh, W. C. 2004. Spacetime patterns of Late Cretaceous to present magmatism in New Mexico – comparison with Andean volcanism and potential for future volcanism. New Mexico Bureau of Geology and Mineral Resources, Bulletin 160:13–40. Socorro, New Mexico.

Christiansen, P. 2013. Phylogeny of the sabertoothed felids (Carnivora: Felidae: Machairodontinae). Cladistics, abstract. 29: 543–559.

Cope, E. D. 1880. On the Extinct Cats of America. American Naturalist. xiv (12):833-857.

Domingo, M. S.; Domingo, L.; Badgley, C.; Sanisidro, O.; and Morales, J. 2013. Resource partitioning among top predators in a Miocene food web. Proceedings of the Royal Society B. 280:2012-2138.

Driscoll, C. A.; Menotti-Raymond, M.; Roca, A. I.; Hupe, K.; Johnson, W. E.; Geffen, E.; Harley, E. H.; Delibes, M.; Pontier, D.; Kitchener, A. C.; Yamaguchi, N.; O’Brien, S. J.; and Macdonald, D. W. 2007. The Near Eastern origin of cat domestication. Science. 317:519-522.

Ezard, T. H. G.; Aze, T.; Pearson, P. N.; and Purvis, A. 2011. Interplay between changing climate and species’ ecology drives macroevolutionary dynamics. Science. 332(6027):349-351.

Farris, D. W.; Jaramillo, C.; Bayona, G.; Restrepo-Moreno, S. A.; and others. 2011. Fracturing of the Panamanian Isthmus during initial collision with South America. Geology. 39(11):1007-1010.

Fossilworks. Machairodus catocopis Cope 1887 (cat). http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=47841.

Gradstein, F. M.; Ogg, J. G.; and Hilgen, F. G. 2012. On the geologic time scale. Newsletters on Stratigraphy. 45(2):171-188.

Heske, E. J. Fall 2013 semester. Mammalogy 462, online class notes. Multiple lectures. http://www.life.illinois.edu/ib/462 . Last accessed December 11, 2015.

Hunt, Jr., R. M. 1989. Biogeography of the Order Carnivora, in Carnivore Behavior, Ecology, and Evolution, ed. J. L. Gittleman, J. L., 2:485–541 Ithaca, NY: Cornell University Press.

—. 2004. Global climate and the evolution of large mammalian carnivores during the later Cenozoic in North America. Bulletin of the American Museum of Natural History. 285:139-156.

Jaramillo, C.; Montes, C.; Cardona, A.; Silvestro, D.; and others. 2017. Comment (1) on “Formation of the Isthmus of Panama” by O’Dea et al. Science Advances. 3:e.1602321.

Johnson, W. E.; Eizirik, E.; Pecon-Slattery, J.; Murphy, W. J.; Antunes, A.; and Teeling, E. C. 2006. The Late Miocene Radiation of Modern Felidae: A Genetic Assessment. Science 311:73-77.

Kitchener, A. C., Van Valkenburgh, B., and Yamaguchi, N. 2010. Felid form and function, in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 83-106. Oxford: Oxford University Press.

Kohn, M. J., and Fremd, T. J. 2008. Miocene tectonics and climate forcing of biodiversity, western United States. Geology, 36 (10):783-786.

Martin, L. D. 1980. Paper 287: Functional Morphology and the Evolution of Cats. Transactions of the Nebraska Academy of Sciences and Affiliated Societies. VIII:141-154.

Nyakatura, K., and Bininda-Emonds, O. R. P. 2012. Updating the evolutionary history of Carnivora (Mammalia): a new species-level supertree complete with divergence time estimates. BMC Biology. 10:12.

O’Brien, S. J. and Johnson, W. E. 2007. The evolution of cats. Scientific American. 297 (1):68-75.

O’Brien, S. J.; Johnson, W.; Driscoll, C.; Pontius, J.; Pecon-Slattery, J.; and Menotti-Raymond, M. 2008. State of cat genomics. Trends in Genetics. 24(6):268-279.

Prothero, D. R. 2004. Did impacts, volcanic eruptions, or climate change affect mammalian evolution? Palaeogeography, Palaeoclimatology, Palaeoecology. 214:283-294.

—. 2006. After the Dinosaurs: The Age of Mammals. Bloomington and Indianapolis : Indiana University Press.

—. 2012. Cenozoic mammals and climate change: The contrast between coarse-scale versus high-resolution studies explained by species sorting. Geosciences. 2:25-41.

Ravelo, A. C.; Andreasen, D. H.; Lyle, M.; Olivarez Lyle, A.; and Wara, M. W. 2004. Regional climate shifts caused by the gradual global cooling in the Pliocene epoch. Nature. 429:263-267.

Rothwell, T. 2003. Phylogenetic Systematics of North American Pseudaelurus (Carnivora: Felidae). American Museum Novitates. 3403:1-64.

Salesa, M. J., Antón, M., Morales, J., and Peigné, S. 2011. Functional anatomy of the postcranial skeleton of Styriofelis lorteti (Carnivora, Felidae, Felinae) from the Middle Miocene (MN 6) locality of Sansan (Gers, France). Estudios Geológicos, 67(2):223-243.

Salesa, M. J.; Antón, M.; Turner, A.; and Morales, J. 2010a. Functional anatomy of the forelimb in Promegantereon ogygia (Felidae, Machairodontinae, Smilodontini) from the the late Miocene of Spain and the origins of the sabre-toothed felid model. Journal of Anatomy. 216:381-396.

Salesa, M. J.; Antón, M.; Turner, A.; Alcala, L.; Montoya, P.; and Morales, J. 2010b. Systematic revision of the late Miocene sabre-toothed felid Paramachaerodus in Spain. Palaeontology. 53(6):1369-1391.

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Spassov, N., and Geraads, D. 2015. A new felid from the Late Miocene of the Balkans and the contents of the genus Metailurus Zdansky, 1924 (Carnivora, Felidae). Journal of Mammal Evolution. 22:45-56.

Sunquist, M. and Sunquist, F. 2002. Wild cats of the world. Chicago and London: University of Chicago Press.

Turner, A., and Antón, M. 1997. The Big Cats and Their Fossil Relatives: An Illustrated Guide to Their Evolution and Natural History. New York: Columbia University Press.

Turner, A., Antón, M., Salesa, M. J., and J. Morales, J. 2011. Changing ideas about the evolution and functional morphology of Machairodontine felids. Estudios Geológicos. 67(2): 255-276.

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van den Hoek Ostende, L., Morlo, M., and Nagel, D. 2006. Fossils explained (52): Majestic killers: the sabretoothed cats. Geology Today. 22(4):150-157.

Van Valkenburgh, B. 1999. Major patterns in the history of carnivorous mammals. Annual Reviews of Earth and Planetary Science. 27:463-493.

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Werdelin, L., and Dehghani, R. 2011. Carnivora, in Paleontology and Geology of Laetoli: Human Evolution in Context, Volume 2: Fossil Hominins and the Associated Fauna, Harrison, T., ed., 189-232. Springer, Dordrecht.

Werdelin, L., and Lewis, M. E.  2001.  A revision of the genus Dinofelis (Mammalia, Felidae). Zoological Journal of the Linnean Society. 132: 147–258.

Werdelin, L.; Yamaguchi, N.; Johnson, W. E.; and O’Brien, S. J.. 2010. Phylogeny and evolution of cats (Felidae), in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 59-82. Oxford: Oxford University Press.


This series on sabertooths was originally posted at my Robin Huntingdon blog about a year ago.


The Sabertooths, Part 5: Smilodon and Homotherium

Here we are in the Pliocene, some two and a half million years before the present.

Plate tectonics has brought North and South America together for the first time, although the exact timing of this junction is debatable, and the first ice age is looming. (Agustí and Antón; Farris and others; Jaramillo and others; Lyle and others)

The most advanced cats ever – Homotherium, Megantereon, and Smilodon – are prowling around, forcing the ancestors of modern cats to keep a low profile, and you and I are at a crossroads.

A series on sabercats must go in one of two different directions at this point.

The usual thing to do next is to discuss the Homotheriini and Smilodontini tribes. We’re going to do this.

But there’s a problem with this two-tribes approach.

Antón adds in yet another tribe – the Metailurini – because they had some sabertooth features. However, another source (Werdelin and others) says that those fossil cats are very hard to herd, i.e., to classify correctly.

I think the Metailurus group fits better into a discussion of some cutting-edge research that defines saber-cats differently and leads to some surprising conclusions (Christiansen), so let’s look at the Metailurini and another toothy cat called Nimravides tomorrow.

The Homotheriini

Quite apart from the whole scimitar- and dirk-tooth thing mentioned earlier this week, Homotheriini and Smilodontini were two very different sabertoothed cat groups.

Generally speaking, Homotherium species tended to be long-legged, like a modern lion. They were also rather lightly built compared to Smilodon. (Turner and Antón; Werdelin and others), although their powerful forearm muscles were also very good at holding down and immobilizing prey. (Werdelin and others)

Xenosmilus was the homotherin exception to this lion-legs rule. Its teeth were rather odd, too.

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Xenosmilus

Meet Xenosmilus hodsonae, which lived in what is now Florida around 1 Ma (million years ago). (Antón)

This cat had the flat, coarsely serrated sabers of a homotherin, but it also had an arc of big incisors and huge scissor-like cheek teeth for slicing meat. (Antón)

Some experts suspect that Xenosmilus used those incisors and lower canines to take out big chunks of flesh instead of what was probably the more typical killing bite that severed a hapless victim’s neck veins and arteries with the saberteeth while clamping down hard on its windpipe. (Naples and others, 2011; Turner and Antón; Wheeler)

However, the strangest thing about this likely relative of Homotherium is that its legs were short and powerful – like those of the Smilodontini. (Antón)

One explanation for this uses an idea called “ecomorphs.”

According to ecomorph theory, certain body types adapt to fit into specific environments. Generally speaking, the cat-like ecomorph goes with a habitat that has both open areas and trees – perfect for a stalk-and-ambush hunter. (Martin, 1989)

Pursuit hunters usually have longer legs than a cat does. The extra length may help these predators conserve energy during the chase. (Andersson and Werdelin)

Since Homotherium generally had long legs, it may have been best adapted to open areas where it could chase prey, perhaps in a group. (Antón)

Xenosmilus, on the other hand, might have evolved after some homotherins moved into a more forested area, where ambush was a better way to hunt. Shorter, more powerful legs, like those of a modern jaguar, would work better here than speedy lion-legs. (Antón; Schellhorn and Sammgaraja)

This is just an hypothesis, since no clearly supporting evidence has been found yet, but it’s an intriguing possibility.

And it’s a reminder of that paleontologists are very aware of something very few of us laypeople ever realize. Most of the important information we use to understand modern cats – things like hunting behavior and socializing – just doesn’t exist in the fossilized remains of extinct cats.

This information gap makes it very difficult for scientists to understand how the sabertoothed cats lived and why they went extinct.

Smilodon

As far as experts know right now, there were only three species of Smilodon, and they all lived in the New World.

The oldest known species is Smilodon gracilis. It was a sturdy sabertooth, the size of a modern jaguar, and resembled Megantereon, although its teeth and skeletal details were more specialized. (Antón)

Gracilis fossils have been found in the eastern and southern US, and as far away as South America. (Wallace and Hulbert)

Next came Smilodon fatalis. This is the movie star; the California state fossil; the Smilodon of Rancho la Brea asphalt pits. (Antón)

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La Brea circa 1910. Any animal or human that carelessly splashed into this deceptively quiet water was trapped and sank into the tarry depths – so did scavengers and predators attracted by the victim’s struggles.

S. fatalis was as tall as a lion but much more of a hulk. A typical adult probably weighed up to 600 pounds (280 kilograms) or more. (Antón)

Its prey was big, too. Over half of the plant-eaters studied at La Brea probably weighed more than 660 pounds (300 kg) in life. (Van Valkenburgh and Hertel)

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Three cheers for those who painstakingly clean sticky tar off fragile fossils without destroying them!

Hundreds of these saber-cats died at La Brea. Their preserved bones have given investigators DNA. (Antón; Barnett and others)

As well, the Fatalis skeletons provide an intriguing look into this cat’s lifestyle and some of the injuries it was prone to (Antón):

  • Smilodon didn’t break its saberteeth any more often than its other teeth, but all of the large carnivores at La Brea – wolves, lions, and coyotes, as well as cats – had more tooth fractures than modern ones do. (Van Valkenburgh and Hertel)
  • Smilodon repeatedly strained its shoulder muscles, probably while pulling in prey.
  • Chronic sternum injuries suggest that Smilodon smashed into prey chest first when it attacked. Yes, I’d like to see a video of that, too.
  • Pulled spinal muscles show how hard it was for even these big sabertooths to hold onto Ice-Age megafauna.
  • Leg and foot fractures probably happened accidentally or as the victim struggled.
  • Fights. One Smilodon skull has a hole in it the size of a Smilodon sabertooth; another saber-cat has a similar hole in its shoulder blade. (Antón) And one wolf skull has part of a Smilodon saber still embedded in its forehead. (Martin, 1980) We’ll never know if the victorious cat was able to survive with just one working sabertooth.

The hole in that one cat’s skull didn’t heal – it died of its wound. Usually, though, these skeletal signs of damage show some mending – the injured cats lived on for a while. (Antón)

One Smilodon broke its neck . . . and the fracture healed. (Rothschild and Martin)

This was one rugged cat!

Gracilis and Fatalis are the only Smilodontini that have been found in North America thus far. (Antón)

But there is a third species known. It developed in South America, where an ambush-and-slash niche went vacant just before sabertoothed cats got there.

Before this smilodontin species appeared, one sabertoothed predator had South America – essentially a gigantic island before bumping into North and Central America – all to itself.

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This is Thylacosmilus atrox. It looks slightly different from the saber-cats because it was a marsupial – a completely different kind of mammal from nimravids, barbourofelids, and cats.

Thylacosmilus developed its impressive saberteeth through convergent evolution.

No one is sure why South America’s marsupial sabertooth went extinct, but the reasons may have involved climate change. (Antón; Turner and Antón)

Both Fatalis and Gracilis, as well as Homotherium and many other North American carnivores and plant-eaters, were able to cross over a land bridge – the Isthmus of Panama – when plate tectonics finally joined North and South America together. (Antón; Prothero, 2006)

With Thylacosmiulus gone, there was plenty of room on the southern continent for Smilodon to evolve, and soon S. populator – one of the biggest sabertoothed mammals ever – appeared. (Antón; Turner and Antón)

That second name doesn’t mean that it was popular. “Populator,” according to sources in Antón, means “he who brings devastation.”

Fair enough for a cat 4 feet high at its incredibly muscular shoulder, good at leaping despite a weight of almost 900 pounds (400 kg), with paws bigger than any living cat’s, and saberteeth protruding half a foot (17 cm) below its jaw. (Antón; Turner and Antón)

If you have Antón’s book, check out Figure 3.67. It’s his illustration of Populator galloping across a field, and here is Antón’s description of how he made that impressive paleoart image.

I know cats move silently, but it’s hard to believe that the ground didn’t rumble and shake when Populator was in a hurry or when it collided with one of the gigantic Pleistocene plant-eaters during an attack.

Smilodon populator and the smaller S. fatalis divided up South America between them during the closing millennia of the Pleistocene, with Populator thriving east of the Andes, from Venezuela to Patagonia, while Fatalis terrorized the lands along the western coast. (Antón; Turner and Antón)

And so the world’s ambush-and-slash niche was occupied until roughly 11,000 years ago, when the last known Homotherium disappeared.

At that point, Smilodon had been extinct for some 2,000 years. (Werdelin and others)

A great quiet did not descend upon the world when the saber-cats went away, because cats with “normal” upper canines were still around and were as vocal as ever.

But since then, Earth has been missing something powerful and terribly beautiful.

To be continued tomorrow.


Images:

Featured image: “Homotherium serum model – Cleveland Museum of Natural History 2014-12-26.” T. Evanson. CC BY-SA 2.0.

Xenosmilus, Gainesville-Florida Museum of Natural History. Jared. CC att 2.0 generic.

La Brea asphalt seep, circa 1910. Public domain.

Smilodon skull from La Brea: James St. John. CC BY 2.0.

Thylacosmilus atrox, American Museum of Natural History. Claire Houck. CC Att-SA 2.0 Generic.


Cited and uncited sources:

Agustí, J. and Antón, M. 2002. Mammoths, sabertooths, and hominids: 65 million years of mammalian evolution in Europe. New York and Chichester: Columbia University Press.

Akhmetiev, M. A., and Beniamovski, V. N. 2009. Paleogene floral assemblages around epicontinental seas and straits in Northern Central Eurasia: proxies for climatic and paleogeographic evolution. Geologica Acta. 7(12):297–309.

Andersson, K., and Werdelin, L. 2003. The evolution of cursorial carnivores in the Tertiary: implications of elbow joint morphology. Proceedings of the Royal Society London B (supplement). 270:S163-S165.

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

Antón, M.; Salesa, M. J.; Galobart, A.; and Tseng, Z. J. 2011. The Plio-Pleistocene scimitar-toothed felid genus Homotherium Fabrini, 1890 (Machairodontinae, Homotherini): diversity, paleogeography, and taxonomic implications. Quaternary Science Reviews. 96:259-268.

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This series on sabertooths was originally posted at my Robin Huntingdon blog about a year ago.


The Sabertooths, Part 4: The First Sabertoothed Cats

The early history of the two major saber-cat tribes isn’t well understood yet. (Martin and others, 2011d; Werdelin and others)

Different paleontologists call the first sabertoothed cats by different names. (Antón; van den Hoek Ostende and others; Werdelin and others) The most controversial names are “Miomachairodus,” “Machairodus,” and “Amphimachairodus.”

“This discussion is far from settled, but at the very least shows that these forms grade into one another.”
— Werdelin and others

While professional fossil-cat herders continue to debate the details and slowly reach a consensus, I have chosen two specific sources to follow, even though they aren’t totally consistent:

  • Mauricio Antón calls those early sabertooths Macharoidus and describes Amphimachairodus as a separate group. (Antón)
  • Werdelin and others suggest that “Miomachairodus,” “Machairodus,” and “Amphimachairodus,” whatever their exact relationships to one another were, are the ancestors – somehow – of Homotherium (Werdelin and others), the scimitar-toothed sabercat.

Okay. Let’s move on to the Mediterranean region as it was in 12 Ma (million years ago), when a time traveler might have seen Machairodus there (at a safe distance) and mistaken it for one of today’s big cats.

Machairodus was generally built like a modern tiger, except for a very narrow face, a longer neck than any big cat has today, and a short tail. (Antón; Turner and Antón)

Machairodus also had saberteeth . . . and advanced ones at that. (Antón)

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Experts have painstakingly pieced Machairodus together from fossil fragments found in a natural carnivore trap near Madrid.

Those sabers are impressive, but they look a little strange to paleontologists. Perhaps “out of place” is a better way to put it.

The saberteeth are so advanced, they might have belonged to Homotherium, but Machairodus doesn’t have the rest of a sabertoothed cat’s features, like massive cranial structures to support powerful jaw muscles, powerful forelimbs, and a short hindlegs. (Antón)

In fact, this very feline animal had long back legs that probably made it quite a good jumper. (Antón; Turner and Antón)

So our time traveler didn’t make it back to today because they saw a tiger-sized sabertoothed cat on the other side of a wide crevice and thought they were safe.

For paleontologists, the saberteeth show that the Homotheriini evolved saberteeth first and then worked out the rest of the cranioskeletal adaptations later. Scientists call this process mosaic evolution. LINK (Antón)

Even without other physical characteristics that would enhance the advantages of saberteeth, Machairodus thrived. (Antón)

Its earliest fossils come from Turkey and Africa. After that, these saber-cats spread out across both Eurasia and North America. (van den Hoek Ostende and others)

Machairodus was the first member of the cat family to reach the size of modern lions and tigers, and it didn’t stop there. One of its most successful species, M. aphanistus, was over 3 feet tall (100 cm) at the shoulder. (Antón)

Perhaps being big offset the lack of other sabertooth features.

Saberteeth allowed for a faster kill. (Antón; Turner and others) Machairodus might not have been able yet to tackle the plant-eating giants that thrived back then, its size meant that it could have taken and eaten prey as big as what today’s big cats can handle. (Deng and others)

Quicker.

This was quite an advantage in a highly competitive environment.

Over time, sabertooths became more efficient as they slowly developed all the other physical marks of an advanced sabertooth. (van den Hoek Ostende and others)

They were ready to go, once they had the whole “sabertooth complex.” (Antón)

This included, but wasn’t limited to, powerful forelegs and shoulders to overpower prey and a long, muscular neck to safely position the sabers for that killing bite. (Antón; Turner and others)

There were still a few limits, though.

Megaherbivores as huge as the junior mastodons that Homotherium would eventually tackle in the Pleistocene existed back in the Miocene (Antón; Agustí and Antón; Prothero, 2006), but they were probably safe from all of the early sabertooths. (Antón)

Machairodus followed smaller prey – zebra-sized migrating horses – out of central and western Asia into Europe, where it found lots of other suitable plant-eaters. (Agustí )

This sabertoothed cat coexisted with the barbourofelids (Agustí ; Antón) and held its own against Europe’s big amphicyonid beardogs and ursids (members of the bear family Ursidae). (Hunt, 1989)

Around 10 Ma, a more advanced sabertooth – Amphimachairodus – replaced Machairodus. (Antón)

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That’s an Amphimachairodus skull (bottom) and drawings of the partial skull of Proailurus, the Dawn Cat (top) – the probable ancestor of Pseudaelurus and therefore of both modern cats and sabercats.

Some fifteen million years of evolution separate the two.

A-Mach was even bigger than Machairodus – almost 4 feet high (120 cm) at the shoulder – and its head was longer and narrower. (Turner and Antón)

This saber-cat also had a very muscular neck, as well as enormous dewclaws for holding onto prey animals like horses and antelope. (Antón)

However, A-Mach still overall looked like a modern cat. (Antón; Werdelin and others)

That is, it was still very primitive.

Today we tend to think the sabertooths were primitive because they went extinct. Actually, Homotherium and Smilodon were very advanced specialists. (Antón; Turner and Antón) It’s today’s cats that are the die-hard conservatives.

No cat owner will be surprised by this, of course, but it shows up not only in mood but also in the cat’s build.

Modern felines still have the general Pseudaelurus body plan. They have just changed the legs and feet a bit to make it easier to move on the ground. (Antón; Turner and Antón)

Sabercats were much more specialized, and they still managed to cover a lot of ground.

A “veritable freeway” for both predators and prey existed across the Bering land bridge between Eurasia and North America. (Prothero, 2006, including quote)

In addition, a tectonic collision between Africa and Eurasia had opened up routes between these two continents.

Primitive members of the elephant family, which would eventually evolve into Ice-Age mastodons and mammoths, ventured out of Africa into the wider world while Eurasian sabertooths followed prey into Africa’s mosaic landscapes of forest and wooded grasslands. (Agustí and Antón; Strömberg)

Fossils of these African sabertoothed cats from as far back as 10-11 Ma are still being excavated and studied. (Antón; Peigné and others)

Perhaps the most impressive to date is Machairodus kabir from Chad. This enormous saber-cat might have weighed almost half a metric ton! (Peigné and others)

That’s plenty big enough to take down plant-eaters weighing close to a ton. (Peigné and others)

Another sabertooth, with the jaw-breaking name of Lokotunjailurus, has been found in both Chad and Kenya. The size of a modern lioness, it goes back to about 7 Ma. (Antón; de Bonis and others)

At first, paleontologists thought this long-limbed, graceful sabertoothed cat was Machairodus. However, further study has shown that Lokotunjailurus was a separate species, with some similarities to Homotherium. (Antón; van den Hoek Ostende and others)

It’s too bad there are no common names for these beautiful animals. The scientific names are so long, especially in a family tree!

Some paleontologists (Werdelin and others) draw a very general family tree of the Homotheriini this way: Machairodus around 12 Ma, through Amphimachairodus at about 10 Ma, to Homotherium.

Perhaps Lokotunjailurus fits in there between Amphimachairodus and Homotherium. (van den Hoek Ostende and others)

Finally, according to phylogenetic computer analyses, Homotherium showed up in Europe around 6 Ma and then in North America two or three million years later. (Werdelin and others)

Its earliest fossils go back to 4 Ma – about when the oldest known “Felis” modern-cat ancestor lived in Greece. The sabercat remains were found in both Africa and the Ukraine, which means that Homotherium could have evolved in either Eurasia or Africa. (Antón and others; Werdelin and others)

The roots of Smilodon’s tribe

Many cat fossils are still buried by time, waiting to be discovered. (Johnson and others)

Smilodon’s ancestors are among the missing. (Antón; Werdelin and others) However, some possible early candidates have been recognized. There was Promegantereon, around 11 to 10 Ma. (Werdelin and others)

It was the size of a puma, with saberteeth that weren’t very long but were flat in cross-section, with a curve. (Salesa and others, 2010b)

Promegantereon was smaller than Machairodus, but it had some of the other sabertooth complex features, including powerful forelegs, a big dewclaw, and a narrow head. (Antón; Turner and Antón)

This saber-cat was still primitive, like Machairodus, but already it was built to wrestle down prey (Salesa and others, 2010a) – a trademark of the Smilodontini hunting style.

Even early on, strength mattered in this group.

Promegantereon hunted deer, antelope (Turner and Antón), and other prey in Eurasia and Africa from about 10 Ma to 8 Ma. Then leopard-sized Paramachaerodus showed up around 8 Ma and held the ambush-and-slash niche for another three million years. (Salesa and others, 2010b)

Paramachaerodus had moderately long, serrated sabers. Its other sabertooth features were a little more developed than Promegantereon’s. (Salesa and others, 2010b; Turner and others)

Smaller saber-cats like these probably coexisted with lion-sized Amphimachairodus by sharing resources in some way that’s not well understood yet. (Werdelin and others)

Perhaps they took refuge in trees, just as modern leopards do today in lion and tiger country. (Antón; Domingo and others)

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Toward the end of the Miocene, Europe’s rich wildlife suffered a crisis that was probably related to global cooling. Barbourofelids and amphicyonid beardogs were among the casualties, but the Knife-Tooths came through it with just some reorganization. (Agustí ; Prothero, 2006; van den Hoek Ostende and others)

In the new Pliocene epoch, Paramachairodus was replaced by Megantereon – an undisputed member of the Smilodontini tribe. (Antón; Hunt, 2004; van den Hoek Ostende and others)

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Megantereon

This jaguar-sized saber-cat got around – ranging across Eurasia, Africa, and North America – but apart from the spectacular skeleton displayed above, few of its fossils have been discovered yet. (Antón; Zhu and others)

As a result, no one is sure when or where Megantereon evolved. (Antón; Zhu and others)

This matters a lot to paleontologists, because the most iconic sabertooth of all – Smilodon – appeared after Megantereon’s arrival.

Everybody, laypeople as well as scientists, wants to know where Smilodon – the dirk-toothed sabercat from California’s La Brea asphalt seeps and the only fossil cat to have appeared in a hit movie (Ice Age) – came from.

Some experts think that Megantereon traveled into North America from Asia and evolved into Smilodon around 2.4 Ma. (Hunt, 2004)

There are other possibilities, for instance, that Smilodon and Megantereon were two groups, or that they and another saber-cat that its discoverers have named Rhizosmilodon shared a common ancestor. (Wallace and Hulbert)

It’s even possible that Megantereon was in Africa around the time of Lokotunjailurus, long before it appeared on other continents. (de Bonis and others)

Anyway, here we are at last, some two and a half million years before the present. The Miocene is far behind us, snow is beginning to fall, and vast areas of the continental polar regions are icing over. (Agustí and Antón)

The most advanced cats to ever walk this Earth – Homotherium, Megantereon, and Smilodon – are now well established and at their peak.

To be continued tomorrow


Images:

Featured image: Megantereon cultridens, Natural History Museum, Basel, Switzerland: Ghedoghedo. CC Att SA 4.0 International. Partial.

Machairodus aphanistus, Museo Arqueológico Regional de la Comunidad de Madrid (Alcalá de Heneres).

Combined image:

  • Top: Proailurus, Cope, E. D. 1880. On the extinct cats of America. American Naturalist. xiv (12):833-857, figure 1.
  • Bottom: Machairodus. Ghedoghedo. SEE PAGE CC att SA 3.0 unported, 2.5 Generic, 2.5 Generic, and 1.0 Generic.

Leopard in tree: Siddarth Maheshwari. CC BY-SA 3.0.

Megantereon, Natural History Museum, Basel, Switzerland: Ghedoghedo. CC Att SA 4.0 International.


Cited and uncited sources:

Agustí, J. and Antón, M. 2002. Mammoths, sabertooths, and hominids: 65 million years of mammalian evolution in Europe. New York and Chichester: Columbia University Press.

Akhmetiev, M. A., and Beniamovski, V. N. 2009. Paleogene floral assemblages around epicontinental seas and straits in Northern Central Eurasia: proxies for climatic and paleogeographic evolution. Geologica Acta. 7(12):297–309.

Andersson, K., and Werdelin, L. 2003. The evolution of cursorial carnivores in the Tertiary: implications of elbow joint morphology. Proceedings of the Royal Society London B (supplement). 270:S163-S165.

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

Antón, M.; Salesa, M. J.; Galobart, A.; and Tseng, Z. J. 2011. The Plio-Pleistocene scimitar-toothed felid genus Homotherium Fabrini, 1890 (Machairodontinae, Homotherini): diversity, paleogeography, and taxonomic implications. Quaternary Science Reviews. 96:259-268.

Averianov, A.; Obraztsova, E.; Danilov, I.; Skutschas, P.; and Jin, J. 2016. First nimravid skull from Asia. Nature, Scientific Reports. doi:10.1038/srep25812.

Barnett, R.; Barnes, I.; Phillips, M. J.; Martin, L. D.; Harington, C. R.; Leonard, J. A.; and Cooper, A. 2005. Evolution of the extinct sabretooths and the American cheetahlike cat. Current Biology, 15(15):R589-R590.

Barnosky, A. D. 2001. Distinguishing the effects of the Red Queen and Court Jester of Miocene mammal evolution in the northern Rocky Mountains. Journal of Vertebrate Paleontology. 21(1):172-185.

Benton, M. J.; Donoghue, P. C. J.; Asher, R. J.; Friedman, M.; Near, T. J.; and Vinther, J. 2015. Constraints on the timescale of animal evolutionary history. Palaeontologia Electronica, 18.1.1FC 1-106. palaeo-electronica.org/content/fc-1.

Benton, M. J. 2009. The Red Queen and the Court Jester: Species diversity and the role of biotic and abiotic factors through time. Science. 323(5915):728-732. Abstract.

Christiansen, P. (2013), Phylogeny of the sabertoothed felids (Carnivora: Felidae: Machairodontinae). Cladistics. 29: 543–559; abstract.
de Bonis, L.; Peigné, S.; Mackaye, H. T.; Likius, A.; Vignaud, P.; and Brunet, M. 2010. New sabre-toothed cats in the Late Miocene of Toros Menalla (Chad). Comptes Rendus Palevol. 9:221-227.

Bryant, H. N. 1991. Phylogenetic Relationships and Systematics of the Nimravidae (Carnivora). Journal of Mammalogy, 72(1):56-78.

Cain, M. L.; Bowman, W. D.; and Hacker, S. D. 2014. Ecology. Sunderland, Massachusetts: Sinauer Associates.

Cope, E. D. 1880. On the Extinct Cats of America. American Naturalist. xiv (12):833-857.

Deng, T.; Zhang, Y-X; Tseng, Z. J.; and Hou, S-K. 2016. A skull of Machairodus horribilis and new evidence for gigantism as a mode of mosaic evolution in machairodonts (Felidae, Carnivora). Vertebrata PalAsiatica. 54(4):302-318.

Domingo, M. S.; Domingo, L.; Badgley, C.; Sanisidro, O.; and Morales, J. 2013. Resource partitioning among top predators in a Miocene food web. Proceedings of the Royal Society B. 280:2012-2138.

Ezard, T. H. G.; Aze, T.; Pearson, P. N.; and Purvis, A. 2011. Interplay between changing climate and species’ ecology drives macroevolutionary dynamics. Science. 332(6027):349-351.

Flynn, J. J., and Galiano, H. 1982. Phylogeny of early Tertiary Carnivora with a description of a new species of Protictis from the middle Eocene of northwestern Wyoming. American Museum Novitates. 2725:1-64.

Gradstein, F. M.; Ogg, J. G.; and Hilgen, F. G. 2012. On the geologic time scale. Newsletters on Stratigraphy. 45(2):171-188.

Heske, E. J. Fall 2013 semester. Mammalogy 462, online class notes. Multiple lectures. http://www.life.illinois.edu/ib/462 . Last accessed December 11, 2015.

Holliday, J. A., and Steppan, S. J. 2004. Evolution of hypercarnivory: the effect of specialization on morphological and taxonomic diversity. Paleobiology. 30(1):108-128.

Hunt, Jr., R. M. 1989. Biogeography of the Order Carnivora, in Carnivore Behavior, Ecology, and Evolution, ed. J. L. Gittleman, J. L., 2:485–541 Ithaca, NY: Cornell University Press.

—. 2004. Global climate and the evolution of large mammalian carnivores during the later Cenozoic in North America. Bulletin of the American Museum of Natural History. 285:139-156.

Johnson, W. E.; Eizirik, E.; Pecon-Slattery, J.; Murphy, W. J.; Antunes, A.; and Teeling, E. C. 2006. The Late Miocene Radiation of Modern Felidae: A Genetic Assessment. Science 311:73-77.

Kemp, T. S. 2006. The origin and early radiation of the therapsid mamma-like reptiles: a paleobiological hypothesis. 19:1231-1247. Journal compilation: European Society for Evolutionary Biology.

Kitchener, A. C., Van Valkenburgh, B., and Yamaguchi, N. 2010. Felid form and function, in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 83-106. Oxford: Oxford University Press.

Martin, L. D. 1980. Paper 287: Functional Morphology and the Evolution of Cats. Transactions of the Nebraska Academy of Sciences and Affiliated Societies. VIII:141-154.

Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 2011 Introduction, The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. Baltimore: The Johns Hopkins University Press.

Martin, L. D.; Babiarz, J. P.; and Naples, V. L. 2011b. The osteology of a cookie-cutter cat, Xenosmilus hodsonae, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 42-97. Baltimore: The Johns Hopkins University Press.

Martin, L. D.; Naples, V. L.; and Babiarz, J. P. 2011c. Revision of the New World Homotheriini, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 185-199. Baltimore: The Johns Hopkins University Press.

Martin, L. D.; Babiarz, J. P.; and Naples, V. L. 2011d. A framework for the North American Homotheriini, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 200-209. Baltimore: The Johns Hopkins University Press.

Morales, M. M., and Giannini, N. P. 2014. Pleistocene extinctions and the perceived morphofunctional structure of the neotropical felid ensemble. Journal of Mammal Evolution. 21:395-405.

O’Brien, S. J. and Johnson, W. E. 2007. The evolution of cats. Scientific American. 297 (1):68-75.

O’Brien, S. J.; Johnson, W.; Driscoll, C.; Pontius, J.; Pecon-Slattery, J.; and Menotti-Raymond, M. 2008. State of cat genomics. Trends in Genetics. 24(6):268-279.

Peigné, S.; de Bonis, L.; Likius, A.; Mackaye, H. T.; Vignaud, P.; and Brunet, M. 2005. A new machairodontine (Carnivora, Felidae) from the Late Miocene hominid locality of TM 266, Toros-Menalla, Chad. Comptes Rendus Palevol. 4:243-253.

Probiner, B. L. 2015. New actualistic data on the ecology and energetics of hominin scavenging opportunities. Journal of Human Evolution. 80:1-16.

Prothero, D. R. 2004. Did impacts, volcanic eruptions, or climate change affect mammalian evolution? Palaeogeography, Palaeoclimatology, Palaeoecology. 214:283-294.

—. 2006. After the Dinosaurs: The Age of Mammals. Bloomington and Indianapolis : Indiana University Press.

Prothero, D. R., and Heaton, T. H. 1996. Faunal stability during the Early Oligocene climatic crash. Palaeogeography, Palaeoclimatology, Palaeoecology. 127:257-283.

Radinsky, L. B. 1982. Evolution of the skull shape in carnivores. 3. The origin and early radiation of the modern carnivore families. Paleobiology. 8(3):177-195.

Ravelo, A. C.; Andreasen, D. H.; Lyle, M.; Olivarez Lyle, A.; and Wara, M. W. 2004. Regional climate shifts caused by the gradual global cooling in the Pliocene epoch. Nature. 429:263-267.

Rothschild, B. M., and Martin, L. D. 2011. Pathology in saber-tooth cats, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 34-41. Baltimore: The Johns Hopkins University Press.

Rothwell, T. 2003. Phylogenetic Systematics of North American Pseudaelurus (Carnivora: Felidae). American Museum Novitates. 3403:1-64.

Salesa, M. J., Antón, M., Morales, J., and Peigné, S. 2011. Functional anatomy of the postcranial skeleton of Styriofelis lorteti (Carnivora, Felidae, Felinae) from the Middle Miocene (MN 6) locality of Sansan (Gers, France). Estudios Geológicos, 67(2):223-243.

Salesa, M. J.; Antón, M.; Turner, A.; and Morales, J. 2010a. Functional anatomy of the forelimb in Promegantereon ogygia (Felidae, Machairodontinae, Smilodontini) from the the late Miocene of Spain and the origins of the sabre-toothed felid model. Journal of Anatomy. 216:381-396.

Salesa, M. J.; Antón, M.; Turner, A.; Alcala, L.; Montoya, P.; and Morales, J. 2010b. Systematic revision of the late Miocene sabre-toothed felid Paramachaerodus in Spain. Palaeontology. 53(6):1369-1391.

Schellhorn, R. and M. Sammugaraja. 2015. Habitat adaptations in the felid forearm. Palaeontol Z confirm 89:261-269.

Smithsonian National Museum of Natural History. Geologic Time: The Story of a Changing Earth. http://paleobiology.si.edu/geotime/main/ Last accessed in summer of 2015.

Strömberg, C. A. E. 2011. Evolution of Grasses and Grassland Ecosystems. Annual Reviews of Earth and Planetary Science. 2011. 39:517-544.

Stuart, A. J. 2015. Late Quaternary megafaunal extinctions on the continents: a short review. Geological Journal. 50:338-363.

Sunquist, M. and Sunquist, F. 2002. Wild cats of the world. Chicago and London: University of Chicago Press.

Turner, A., and Antón, M. 1997. The Big Cats and Their Fossil Relatives: An Illustrated Guide to Their Evolution and Natural History. New York: Columbia University Press.

Turner, A., Antón, M., Salesa, M. J., and J. Morales, J. 2011. Changing ideas about the evolution and functional morphology of Machairodontine felids. Estudios Geológicos. 67(2): 255-276.

van den Hoek Ostende, L., Morlo, M., and Nagel, D. 2006. Fossils explained (52): Majestic killers: the sabretoothed cats. Geology Today. 22(4):150-157.

Van Valkenburgh, B. 1999. Major patterns in the history of carnivorous mammals. Annual Reviews of Earth and Planetary Science. 27:463-493.

—. 2007. Déjà vu: the evolution of feeding morphologies in the Carnivora. Integrative and Comparative Biology. 47 (1):147-163.

Van Valkenburgh, B., and Hertel, F. 1993. Tough times at La Brea: Tooth breakage in large carnivores of the late Pleistocene. Science, New Series. 261(5120):456-459.

Wallace, S. C., and Hulbert, Jr., R. C. 2013. A new machairodont from the Palmetto Fauna (Early Pliocene) of Florida, with comments on the origin of the Smilodontini (Mammalia, Carnivora, Felidae). PLoS ONE. 8(3): e56173.

Webb, S. D. 1987. Community patterns in extinct terrestrial vertebrates, in Organization of Communities Past and Present, ed. Gee, J. H. R. and Giller, P. S., 439-466. Oxford: Blackwell Scientific Publications.

Werdelin, L. 1989. Carnivoran Ecomorphology: A Phylogenetic Perspective, in Carnivore Behavior, Ecology, and Evolution, ed. Gittleman, J. L., 2:582-624. Ithaca, NY: Cornell University Press.

Werdelin, L.; Yamaguchi, N.; Johnson, W. E.; and O’Brien, S. J.. 2010. Phylogeny and evolution of cats (Felidae), in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 59-82. Oxford: Oxford University Press.

Wesley-Hunt, G. D. 2005. The Morphological Diversification of Carnivores in North America. Paleobiology, 31(1):35-55.

Wheeler, H. T. 2011. Experimental paleontology of the scimitar-tooth and dirk-tooth killing bites, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P., 19-33. Baltimore: The Johns Hopkins University Press.

Yamaguchi, N., Driscoll, C. A., Kitchener, A. C., Ward, J. M., and Macdonald, D. W. 2004. Craniological differentiation between European wildcats (Felis silvestris silvestris), African wildcats (F. s. lybica) and Asian wildcats (F. s. ornata): implications for their evolution and conservation. Biological Journal of the Linnean Society. 83:47-63.

Zhu, M.; Schubert, B. W.; Liu, J.; and Wallace, J. C. 2014. A new record of the saber-toothed cat Megantereon (Felidae, Machairodontinae) from an Early Pleistocene Gigantopithecus fauna, Yanliang Cave, Fusui, Guangxi, South China. Quaternary International. 354:100-109.


This series on sabertooths was originally posted at my Robin Huntingdon blog about a year ago.


The Sabertooths, Part 3: Sabertooths Down Through Time

Saberteeth aren’t all that unusual in fossil carnivores.

Since the K/T extinction sixty-five million years ago, at least four mammal groups have had them. (Kitchener and others)

Members of all four, plus the very first sabertooths – Permian gorgonopsids – are shown here, drawn to scale:

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That must be The Doctor. Only a Time Lord could get into such a predicament – millions of years actually separate some of these animals from the others.
Continue reading

The Sabertooths, Part 2: Saberteeth

Saberteeth are a cat’s upper fangs, flattened as well as lengthened. Modern cats don’t have them, even though they are hypercarnivores just like their extinct sabercat cousins.

Hypercarnivores need at least 70% of their diet to come from meat. This is why Fluffy the Housecat can’t live on dog food – it needs the special balance of protein and amino acids that canned and dry cat food contains.

In the wild, cats depend on prey animals. To survive, their canine teeth have evolved into fangs. (Holliday and Steppan; Kitchener and others)

Bengal tigers have the largest fangs of any modern cat – up to 4 inches (10 cm) long. (Heske, Lab 19)

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The fangs of this Brazilian jaguar along the Rio Negro are impressive, too.

In comparison, Smilodon’s saberteeth were almost a foot (28 cm) long! (van den Hoek Ostende and others)

But those weren’t really fangs.

In today’s big cats, fangs are rather cone-shaped – thick at the base and tapering up into a rounded point.

Saberteeth were much flatter, front to back, than the fangs of any “normal” modern cat. (Martin, 1980; van den Hoek Ostende and others)

The edges looked like knives. Indeed, the technical name for sabertoothed cats is Machairodontinae, which means “Knife-Tooths.” (Antón; Turner and others)

But appearances are deceptive. Saberteeth were actually blunter than a steel blade, although sometimes they were serrated. (Turner and Antón)

Mechanical experiments show that saberteeth could only cut through hide and animal tissues when the cat also made a slicing movement during its killing bite. (Wheeler)

Hence the name ambush-and-slash for a sabertoothed predator’s hunting style. In contrast, all modern cats use a stalk-and-pounce hunting technique. (Werdelin, 1989)

Paleontologists have found subtle differences in saberteeth between two major sabertoothed cat tribes, the Homotheriini and the Smilodontini.

Homotherium and its relatives were scimitar-toothed. Their saberteeth tended to be broad and very flat, with coarse serrations. (Antón; Martin, 1980)

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Homotherium

The Smilodontini were dirk-toothed cats. Their sabers were generally longer and straighter, less flattened, and with very fine serrations to none at all. (Antón; Martin, 1980)

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Smilodon populator was an extreme dirk-tooth. (Note: Per Antón, the species name “necator” isn’t used any more.)

These differences matter a lot to experts since they may provide some clues as to how each apex predator used its teeth and fit into those long-vanished ecosystems.

But for general purposes, it’s still perfectly okay to just call them all sabertooths.

But not all sabertooths were members of the cat family.

To be continued tomorrow


Images

Featured image: Hoplophoneus primaevus, by James St. John, Flickr. CC BY 2.0.

Yawning jaguar: Charles J. Sharp, Sharp Photography, Flickr. CC BY-SA 4.0.

Homotherium crenatidens, Muséum national d’Histoire naturelle, Paris: Ghedo. Public domain.

Smilodon upper skull: Cope, E. D. 1880. On the extinct cats of America. American Naturalist. xiv (12):833-857, figure 13.


Cited and uncited sources:

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Cain, M. L.; Bowman, W. D.; and Hacker, S. D. 2014. Ecology. Sunderland, Massachusetts: Sinauer Associates.

Cope, E. D. 1880. On the Extinct Cats of America. American Naturalist. xiv (12):833-857.

Deng, T.; Zhang, Y-X; Tseng, Z. J.; and Hou, S-K. 2016. A skull of Machairodus horribilis and new evidence for gigantism as a mode of mosaic evolution in machairodonts (Felidae, Carnivora). Vertebrata PalAsiatica. 54(4):302-318.

Domingo, M. S.; Domingo, L.; Badgley, C.; Sanisidro, O.; and Morales, J. 2013. Resource partitioning among top predators in a Miocene food web. Proceedings of the Royal Society B. 280:2012-2138.

Ezard, T. H. G.; Aze, T.; Pearson, P. N.; and Purvis, A. 2011. Interplay between changing climate and species’ ecology drives macroevolutionary dynamics. Science. 332(6027):349-351.

Flynn, J. J., and Galiano, H. 1982. Phylogeny of early Tertiary Carnivora with a description of a new species of Protictis from the middle Eocene of northwestern Wyoming. American Museum Novitates. 2725:1-64.

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Holliday, J. A., and Steppan, S. J. 2004. Evolution of hypercarnivory: the effect of specialization on morphological and taxonomic diversity. Paleobiology. 30(1):108-128.

Hunt, Jr., R. M. 1989. Biogeography of the Order Carnivora, in Carnivore Behavior, Ecology, and Evolution, ed. J. L. Gittleman, J. L., 2:485–541 Ithaca, NY: Cornell University Press.

—. 2004. Global climate and the evolution of large mammalian carnivores during the later Cenozoic in North America. Bulletin of the American Museum of Natural History. 285:139-156.

Johnson, W. E.; Eizirik, E.; Pecon-Slattery, J.; Murphy, W. J.; Antunes, A.; and Teeling, E. C. 2006. The Late Miocene Radiation of Modern Felidae: A Genetic Assessment. Science 311:73-77.

Kemp, T. S. 2006. The origin and early radiation of the therapsid mamma-like reptiles: a paleobiological hypothesis. 19:1231-1247. Journal compilation: European Society for Evolutionary Biology.

Kitchener, A. C., Van Valkenburgh, B., and Yamaguchi, N. 2010. Felid form and function, in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 83-106. Oxford: Oxford University Press.

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Martin, L. D.; Babiarz, J. P.; and Naples, V. L. 2011b. The osteology of a cookie-cutter cat, Xenosmilus hodsonae, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 42-97. Baltimore: The Johns Hopkins University Press.

Martin, L. D.; Naples, V. L.; and Babiarz, J. P. 2011c. Revision of the New World Homotheriini, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 185-199. Baltimore: The Johns Hopkins University Press.

Martin, L. D.; Babiarz, J. P.; and Naples, V. L. 2011d. A framework for the North American Homotheriini, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 200-209. Baltimore: The Johns Hopkins University Press.

Morales, M. M., and Giannini, N. P. 2014. Pleistocene extinctions and the perceived morphofunctional structure of the neotropical felid ensemble. Journal of Mammal Evolution. 21:395-405.

O’Brien, S. J. and Johnson, W. E. 2007. The evolution of cats. Scientific American. 297 (1):68-75.

O’Brien, S. J.; Johnson, W.; Driscoll, C.; Pontius, J.; Pecon-Slattery, J.; and Menotti-Raymond, M. 2008. State of cat genomics. Trends in Genetics. 24(6):268-279.

Peigné, S.; de Bonis, L.; Likius, A.; Mackaye, H. T.; Vignaud, P.; and Brunet, M. 2005. A new machairodontine (Carnivora, Felidae) from the Late Miocene hominid locality of TM 266, Toros-Menalla, Chad. Comptes Rendus Palevol. 4:243-253.

Probiner, B. L. 2015. New actualistic data on the ecology and energetics of hominin scavenging opportunities. Journal of Human Evolution. 80:1-16.

Prothero, D. R. 2004. Did impacts, volcanic eruptions, or climate change affect mammalian evolution? Palaeogeography, Palaeoclimatology, Palaeoecology. 214:283-294.

—. 2006. After the Dinosaurs: The Age of Mammals. Bloomington and Indianapolis : Indiana University Press.

Prothero, D. R., and Heaton, T. H. 1996. Faunal stability during the Early Oligocene climatic crash. Palaeogeography, Palaeoclimatology, Palaeoecology. 127:257-283.

Radinsky, L. B. 1982. Evolution of the skull shape in carnivores. 3. The origin and early radiation of the modern carnivore families. Paleobiology. 8(3):177-195.

Ravelo, A. C.; Andreasen, D. H.; Lyle, M.; Olivarez Lyle, A.; and Wara, M. W. 2004. Regional climate shifts caused by the gradual global cooling in the Pliocene epoch. Nature. 429:263-267.

Rothschild, B. M., and Martin, L. D. 2011. Pathology in saber-tooth cats, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 34-41. Baltimore: The Johns Hopkins University Press.

Rothwell, T. 2003. Phylogenetic Systematics of North American Pseudaelurus (Carnivora: Felidae). American Museum Novitates. 3403:1-64.

Salesa, M. J., Antón, M., Morales, J., and Peigné, S. 2011. Functional anatomy of the postcranial skeleton of Styriofelis lorteti (Carnivora, Felidae, Felinae) from the Middle Miocene (MN 6) locality of Sansan (Gers, France). Estudios Geológicos, 67(2):223-243.

Salesa, M. J.; Antón, M.; Turner, A.; and Morales, J. 2010a. Functional anatomy of the forelimb in Promegantereon ogygia (Felidae, Machairodontinae, Smilodontini) from the the late Miocene of Spain and the origins of the sabre-toothed felid model. Journal of Anatomy. 216:381-396.

Salesa, M. J.; Antón, M.; Turner, A.; Alcala, L.; Montoya, P.; and Morales, J. 2010b. Systematic revision of the late Miocene sabre-toothed felid Paramachaerodus in Spain. Palaeontology. 53(6):1369-1391.

Schellhorn, R. and M. Sammugaraja. 2015. Habitat adaptations in the felid forearm. Palaeontol Z confirm 89:261-269.

Smithsonian National Museum of Natural History. Geologic Time: The Story of a Changing Earth. http://paleobiology.si.edu/geotime/main/ Last accessed in summer of 2015.

Strömberg, C. A. E. 2011. Evolution of Grasses and Grassland Ecosystems. Annual Reviews of Earth and Planetary Science. 2011. 39:517-544.

Stuart, A. J. 2015. Late Quaternary megafaunal extinctions on the continents: a short review. Geological Journal. 50:338-363.

Sunquist, M. and Sunquist, F. 2002. Wild cats of the world. Chicago and London: University of Chicago Press.

Turner, A., and Antón, M. 1997. The Big Cats and Their Fossil Relatives: An Illustrated Guide to Their Evolution and Natural History. New York: Columbia University Press.

Turner, A., Antón, M., Salesa, M. J., and J. Morales, J. 2011. Changing ideas about the evolution and functional morphology of Machairodontine felids. Estudios Geológicos. 67(2): 255-276.

van den Hoek Ostende, L., Morlo, M., and Nagel, D. 2006. Fossils explained (52): Majestic killers: the sabretoothed cats. Geology Today. 22(4):150-157.

Van Valkenburgh, B. 1999. Major patterns in the history of carnivorous mammals. Annual Reviews of Earth and Planetary Science. 27:463-493.

—. 2007. Déjà vu: the evolution of feeding morphologies in the Carnivora. Integrative and Comparative Biology. 47 (1):147-163.

Van Valkenburgh, B., and Hertel, F. 1993. Tough times at La Brea: Tooth breakage in large carnivores of the late Pleistocene. Science, New Series. 261(5120):456-459.

Wallace, S. C., and Hulbert, Jr., R. C. 2013. A new machairodont from the Palmetto Fauna (Early Pliocene) of Florida, with comments on the origin of the Smilodontini (Mammalia, Carnivora, Felidae). PLoS ONE. 8(3): e56173.

Webb, S. D. 1987. Community patterns in extinct terrestrial vertebrates, in Organization of Communities Past and Present, ed. Gee, J. H. R. and Giller, P. S., 439-466. Oxford: Blackwell Scientific Publications.

Werdelin, L. 1989. Carnivoran Ecomorphology: A Phylogenetic Perspective, in Carnivore Behavior, Ecology, and Evolution, ed. Gittleman, J. L., 2:582-624. Ithaca, NY: Cornell University Press.

Werdelin, L.; Yamaguchi, N.; Johnson, W. E.; and O’Brien, S. J.. 2010. Phylogeny and evolution of cats (Felidae), in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 59-82. Oxford: Oxford University Press.

Wesley-Hunt, G. D. 2005. The Morphological Diversification of Carnivores in North America. Paleobiology, 31(1):35-55.

Wheeler, H. T. 2011. Experimental paleontology of the scimitar-tooth and dirk-tooth killing bites, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P., 19-33. Baltimore: The Johns Hopkins University Press.

Yamaguchi, N., Driscoll, C. A., Kitchener, A. C., Ward, J. M., and Macdonald, D. W. 2004. Craniological differentiation between European wildcats (Felis silvestris silvestris), African wildcats (F. s. lybica) and Asian wildcats (F. s. ornata): implications for their evolution and conservation. Biological Journal of the Linnean Society. 83:47-63.

Zhu, M.; Schubert, B. W.; Liu, J.; and Wallace, J. C. 2014. A new record of the saber-toothed cat Megantereon (Felidae, Machairodontinae) from an Early Pleistocene Gigantopithecus fauna, Yanliang Cave, Fusui, Guangxi, South China. Quaternary International. 354:100-109.


This series on sabertooths was originally posted at my Robin Huntingdon blog about a year ago.


The Sabertooths, Part 1

A multi-million-year predator niche has been empty for roughly the last 11,000 years.

We should be celebrating that fact. Instead, we wish they were still around!

Well, it’s understandable. If safety could be guaranteed, who wouldn’t want to go see a live sabertoothed cat at the zoo?

If…

Paleontologists have gotten DNA from well-preserved fossils of the two most famous sabertooths – Smilodon and Homotherium. (Barnett and others)

But if Jurassic Park-style cloning really worked (they’re working on it), safety could not be guaranteed in the saber-cat enclosure.

Nobody knows how these extinct animals behaved.

Some sabertoothed cats were probably good jumpers (Morales and others); most could climb; and a few behemoths had the brutal momentum that a half-ton body mass makes possible when they charged. (Antón; Turner and Antón)

Anyway, they were all cats and therefore moody, quick to react, and unpredictable.

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A modern human would be eyeball-to-eyeball with Smilodon populator here.

Yet, despite the risks, we all so want to see a sabertoothed cat!

The idea of a living sabertooth isn’t total fantasy. It’s very unlikely, but a new one really could appear any day.

After all, evolution is still going on.

And for the last fifty million years (Antón), that ambush-and-slash niche for sabertoothed mammals has always been refilled after a brief vacancy. Then it has been occupied for tens of millions of years at a stretch.

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We could all go back to caves . . .

It’s good to be an apex predator.

Cats didn’t invent saberteeth. These killing tools go back to the days before mammals.

How did cats get them and why aren’t there any sabertooths around today?

To be continued tomorrow


IMAGES:
Featured image: Barbourofelis fricki, Museo di Paleontologia di Firenze: Ghedoghedo. CC-SA 3.0. Edited by BJD.

Smilodon populator, Hungarian Natural History Museum: Tiberio. Public domain.

Barbourofelis loveorum, Florida Museum of National History Fossil Hall at University of Florida: Dallas Krentzel. CC-BY 2.0.


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Akhmetiev, M. A., and Beniamovski, V. N. 2009. Paleogene floral assemblages around epicontinental seas and straits in Northern Central Eurasia: proxies for climatic and paleogeographic evolution. Geologica Acta. 7(12):297–309.

Andersson, K., and Werdelin, L. 2003. The evolution of cursorial carnivores in the Tertiary: implications of elbow joint morphology. Proceedings of the Royal Society London B (supplement). 270:S163-S165.

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

Antón, M.; Salesa, M. J.; Galobart, A.; and Tseng, Z. J. 2011. The Plio-Pleistocene scimitar-toothed felid genus Homotherium Fabrini, 1890 (Machairodontinae, Homotherini): diversity, paleogeography, and taxonomic implications. Quaternary Science Reviews. 96:259-268.

Averianov, A.; Obraztsova, E.; Danilov, I.; Skutschas, P.; and Jin, J. 2016. First nimravid skull from Asia. Nature, Scientific Reports. doi:10.1038/srep25812.

Barnett, R.; Barnes, I.; Phillips, M. J.; Martin, L. D.; Harington, C. R.; Leonard, J. A.; and Cooper, A. 2005. Evolution of the extinct sabretooths and the American cheetahlike cat. Current Biology, 15(15):R589-R590.

Barnosky, A. D. 2001. Distinguishing the effects of the Red Queen and Court Jester of Miocene mammal evolution in the northern Rocky Mountains. Journal of Vertebrate Paleontology. 21(1):172-185.

Benton, M. J.; Donoghue, P. C. J.; Asher, R. J.; Friedman, M.; Near, T. J.; and Vinther, J. 2015. Constraints on the timescale of animal evolutionary history. Palaeontologia Electronica, 18.1.1FC 1-106. palaeo-electronica.org/content/fc-1.

Benton, M. J. 2009. The Red Queen and the Court Jester: Species diversity and the role of biotic and abiotic factors through time. Science. 323(5915):728-732. Abstract.

Christiansen, P. (2013), Phylogeny of the sabertoothed felids (Carnivora: Felidae: Machairodontinae). Cladistics. 29: 543–559; abstract.
de Bonis, L.; Peigné, S.; Mackaye, H. T.; Likius, A.; Vignaud, P.; and Brunet, M. 2010. New sabre-toothed cats in the Late Miocene of Toros Menalla (Chad). Comptes Rendus Palevol. 9:221-227.

Bryant, H. N. 1991. Phylogenetic Relationships and Systematics of the Nimravidae (Carnivora). Journal of Mammalogy, 72(1):56-78.

Cain, M. L.; Bowman, W. D.; and Hacker, S. D. 2014. Ecology. Sunderland, Massachusetts: Sinauer Associates.

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Deng, T.; Zhang, Y-X; Tseng, Z. J.; and Hou, S-K. 2016. A skull of Machairodus horribilis and new evidence for gigantism as a mode of mosaic evolution in machairodonts (Felidae, Carnivora). Vertebrata PalAsiatica. 54(4):302-318.

Domingo, M. S.; Domingo, L.; Badgley, C.; Sanisidro, O.; and Morales, J. 2013. Resource partitioning among top predators in a Miocene food web. Proceedings of the Royal Society B. 280:2012-2138.

Ezard, T. H. G.; Aze, T.; Pearson, P. N.; and Purvis, A. 2011. Interplay between changing climate and species’ ecology drives macroevolutionary dynamics. Science. 332(6027):349-351.

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Martin, L. D.; Babiarz, J. P.; and Naples, V. L. 2011b. The osteology of a cookie-cutter cat, Xenosmilus hodsonae, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 42-97. Baltimore: The Johns Hopkins University Press.

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Martin, L. D.; Babiarz, J. P.; and Naples, V. L. 2011d. A framework for the North American Homotheriini, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P. 200-209. Baltimore: The Johns Hopkins University Press.

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Peigné, S.; de Bonis, L.; Likius, A.; Mackaye, H. T.; Vignaud, P.; and Brunet, M. 2005. A new machairodontine (Carnivora, Felidae) from the Late Miocene hominid locality of TM 266, Toros-Menalla, Chad. Comptes Rendus Palevol. 4:243-253.

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Salesa, M. J.; Antón, M.; Turner, A.; and Morales, J. 2010a. Functional anatomy of the forelimb in Promegantereon ogygia (Felidae, Machairodontinae, Smilodontini) from the the late Miocene of Spain and the origins of the sabre-toothed felid model. Journal of Anatomy. 216:381-396.

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Wallace, S. C., and Hulbert, Jr., R. C. 2013. A new machairodont from the Palmetto Fauna (Early Pliocene) of Florida, with comments on the origin of the Smilodontini (Mammalia, Carnivora, Felidae). PLoS ONE. 8(3): e56173.

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Werdelin, L. 1989. Carnivoran Ecomorphology: A Phylogenetic Perspective, in Carnivore Behavior, Ecology, and Evolution, ed. Gittleman, J. L., 2:582-624. Ithaca, NY: Cornell University Press.

Werdelin, L.; Yamaguchi, N.; Johnson, W. E.; and O’Brien, S. J.. 2010. Phylogeny and evolution of cats (Felidae), in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 59-82. Oxford: Oxford University Press.

Wesley-Hunt, G. D. 2005. The Morphological Diversification of Carnivores in North America. Paleobiology, 31(1):35-55.

Wheeler, H. T. 2011. Experimental paleontology of the scimitar-tooth and dirk-tooth killing bites, in The Other Saber-tooths: Scimitar-tooth cats of the Western Hemisphere, eds. Naples, V. L.; Martin, L. D.; and Babiarz, J. P., 19-33. Baltimore: The Johns Hopkins University Press.

Yamaguchi, N., Driscoll, C. A., Kitchener, A. C., Ward, J. M., and Macdonald, D. W. 2004. Craniological differentiation between European wildcats (Felis silvestris silvestris), African wildcats (F. s. lybica) and Asian wildcats (F. s. ornata): implications for their evolution and conservation. Biological Journal of the Linnean Society. 83:47-63.

Zhu, M.; Schubert, B. W.; Liu, J.; and Wallace, J. C. 2014. A new record of the saber-toothed cat Megantereon (Felidae, Machairodontinae) from an Early Pleistocene Gigantopithecus fauna, Yanliang Cave, Fusui, Guangxi, South China. Quaternary International. 354:100-109.


This series on sabertooths was originally posted at my Robin Huntingdon blog about a year ago.


“False” sabertooths and real sabercats


Fact: Before sabercats, there were sabertoothed cat-like apex predators called barbourofelids and nimravids.


Does it matter if the ferocious sabertooth that’s about to attack you lacks the right bone structure to convince scientists it’s a cat?

Only if you are a paleontologist or other expert in ancient life.

As for the rest of us, luckily, time has made us secure against all things sabertooth. We can safely check out the three major long-toothed “cat” groups that have terrorized the planet at various times since the dinosaurs went away.

1. Machairodontinae

Paleontologists classify sabercats as Machairodontinae – “Knife-Tooths.” (Antón; Turner and others)

That reconstructed cat up above is Smilodon fatalis, the famous sabertooth from California’s La Brea “tar” pits.

Unlike the other Ice-Age sabercat – Homotherium – Smilodon was strictly a New World animal. (Antón; Hulbert and Valdes)

As a group, Knife-Tooths were very successful, with a run of at least twelve million years before they finally disappeared at the end of the last ice age. (Agustí and Antón; Antón; Turner and Antón)

2. Barbourofelidae

The terrifying skull, lower right, is a head shot of Barbourofelis fricki.

It was the last, and biggest, of a long line of cat-like “false” sabertooths that lived in Europe, Asia, Africa, and North America during the second half of the Miocene epoch. (Antón; Bryant)

Barbourofelids were apex predators that the first true cats had to face while the cat family Felidae quietly evolved in the bushes and forest canopies of Europe.

Barbourofelid saberteeth were very real. It’s their connection to the cat family that paleontologists aren’t sure of.

Barbourofelids were short-faced hypercarnivores similar to true cats, with much the same build. (Antón; Werdelin and others)

However, their fossils are just different enough from cats for experts to keep them in a separate family for now. (Bryant; Werdelin and others)

3. Nimravidae

Those saberteeth shown on the lower left – belonging to Eusmilus cerebralis – would be impressive if they weren’t in such a picture.

But imagine a large housecat with them. Yikes!

That’s roughly how big E. cerebralis was. (Antón)

Eusmilus and other nimravids, some of which were very large, are the second and earlier group of “false” sabertooths.

In many ways, nimravids outdid the true sabercats. Besides having big sabers in very small animals, which never happened in cats, several of the complex cranial and body anatomy features that support a sabertooth lifestyle were also more advanced. (Werdelin)

That’s strange, because nimravids are very old. So old that the continents were in a slightly different configuration in their day. (Antón; Bryant; Agustí and Antón; Prothero; Werdelin and others)

In the fossil record, five to ten million years separate the last nimravid and the first barbourofelid. (Antón)

That’s the last nimravid.  No one knows how or when nimravids developed into Earth’s very first cat-like predators.

Their oldest fossils go back at least thirty-five million years, but according to some research, the group may be at least fifteen million years older than that. (Averianov and others; Peigné)

So here we are today.  It’s very cool that predators have had a feline appearance for tens of millions of years.

Which one was the biggest and baddest: true cats or one of the “false” sabertooths?

Well, each group was big and bad enough to dominate its ecosystem.  Unfortunately, scientists still know very little about the complex environments that barbourofelids and nimravids lived in.

That leaves us with just a human scale to measure these predators with – and when it comes to love and a sort of fearful fascination, Smilodon wins paws down.

How else could this happen?


IMAGES:
Featured image:

    • Barbourofelis fricki, Museo di Paleontologia di Firenze: Ghedoghedo. CC BY-SA 3.0. Modified by Barb Beier.
    • Eusmilus cerebralis (olsontau), Dallas Krentzel. CC BY 2.0.

 

 


CITED AND UNCITED REFERENCES:

Agustí, J. and Antón, M. 2002. Mammoths, sabertooths, and hominids: 65 million years of mammalian evolution in Europe. New York and Chichester: Columbia University Press.

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

Averianov, A.; Obraztsova, E.; Danilov, I.; Skutschas, P.; and Jin, J. 2016. First nimravid skull from Asia. Nature, Scientific Reports. doi:10.1038/srep25812.

Barrett, P. Z. 2016. Taxonomic and systematic revisions to the North American Nimravidae (Mammalia, Carnivora). PeerJ. 4:31658. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4756750/ Last accessed August 28, 2017.

Bryant, H. N. 1991. Phylogenetic Relationships and Systematics of the Nimravidae (Carnivora). Journal of Mammalogy, 72(1):56-78.

Gradstein, F. M.; Ogg, J. G.; and Hilgen, F. G. 2012. On the geologic time scale. Newsletters on Stratigraphy. 45(2):171-188.

Heske, E. J. Fall 2013 semester. Mammalogy 462, online class notes. Multiple lectures. http://www.life.illinois.edu/ib/462 . Last accessed December 11, 2015.

Hulbert, Jr., R. C., and Valdes, N. 2015. Smilodon fatalis. Florida Museum, University of Florida. https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/species/smilodon-fatalis/ Last accessed August 28, 2017.

Peigné, S. 2003. Systematic review of European Nimravinae (Mammalia, Carnivora, Nimravidae) and the phylogenetic relationships of Palaeogene Nimravidae. Zoologica Scripta. 32(3):199-299.

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

Turner, A., and Antón, M. 1997. The Big Cats and Their Fossil Relatives: An Illustrated Guide to Their Evolution and Natural History. New York: Columbia University Press.

Turner, A., Antón, M., Salesa, M. J., and J. Morales, J. 2011. Changing ideas about the evolution and functional morphology of Machairodontine felids. Estudios Geológicos. 67(2): 255-276.

Werdelin, L. 1996. Carnivoran Ecomorphology: A Phylogenetic Perspective, in Carnivore Behavior, Ecology, and Evolution, ed. Gittleman, J. L., 2:582-624. Ithaca, NY: Cornell University Press.

Werdelin, L.; Yamaguchi, N.; Johnson, W. E.; and O’Brien, S. J.. 2010. Phylogeny and evolution of cats (Felidae), in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 59-82. Oxford: Oxford University Press.

Wright, M., and Walters, S. 1980. The Book of the Cat New York: Summit Books.

 

Homotherium – The Other Ice-Age Sabercat

Mention a sabertoothed cat and most people think of Smilodon. But this apex predator was a strictly New World cat.

The other Pleistocene sabertooth – Homotherium – ranged over all the northern continents, as well as Africa and possibly parts of South America. (Antón; Rincón and others; Turner and others)

It definitely was the more successful of these two sabertooths, but it’s also more of a mystery.

Paleontologists debate Homotherium’s origins and how many species it had, but perhaps their biggest question is how it used its legs.

Unlike Smilodon, which had short legs and a massive body, Homotherium resembled a modern lion, probably without the mane, but with long, graceful legs. This was in addition to the typical sabertooth features of powerful forelimbs, a long neck, and a short back. (Antón)

Those muscular front legs were somewhat longer than a lion’s.  This gave Homotherium a hyena-like body shape, especially in North America, where these cats had a very short back and hind legs (Antón), as shown in the image at the top of this post.

Paleontologists don’t know why Homotherium evolved this way. No modern cat has a locomotion setup like this, so the experts can only theorize over it.

Some think that the long legs and associated features mean that Homotherium hunted on open ground, while Smilodon probably lurked behind cover and ambushed its prey. (Turner and others)

Bolstering this view are Homotherium’s less retractile claws – a feature which cheetahs also have. (Antón)

Not everybody is on board with this, but no one argues with Turner and Antón when they write that ” . . . the appearance of Homotherium suggests something unique among the cats.”

Maybe someday we will figure out what made “the other ice-age sabercat” so special.


Featured image: Skb8721 at the English language Wikipedia. CC BY-SA 3.0.


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

Rincón, A. D.; Prevosti, F. J.; and Parra. 2011. New saber-toothed cat records (Felidae: Machairodontinae) for the Pleistocene of Venezuela, and the Great American Biotic Interchange. Journal of Vertebrate Paleontology. 31(2):468-478.

Turner, A., and M. Antón. 1997. The Big Cats and Their Fossil Relatives: An Illustrated Guide to Their Evolution and Natural History. New York: Columbia University Press.

Turner, A., Antón, M., Salesa, M. J., and Morales, J. 2011. Changing ideas about the evolution and functional morphology of Machairodontine felids. Estudios Geológicos. 67(2): 255-276.

Smilodon Times Three

Everybody has heard of Smilodon, even if they can’t name any of the other sabertoothed cats that have terrorized the planet over the last 12 milliion years or so.

But did you know that there were at least three different Smilodons?

We must use scientific names for them, because our ancestors, who were around during the sabercats’ reign, left no record of what they called these beasts. (Antón)

“Smilodon” is the genus. The oldest known species is S. gracilis, as big as a modern jaguar. (Antón) Its fossils have been found in South America as well as the eastern and central US. (Wallace and Hubert)

Next came S. fatalis, the glamour puss of this group. Lion-sized but more powerful than a modern tiger (Antón), Fatalis lived all over North America, including in what’s now Los Angeles, where its remains at La Brea inspired Californians to make Smilodon the state’s official fossil and to cast this sabercat in a movie role – Ice Age.

And then there was S. populator, the largest sabertooth carnivore that has ever lived. (Antón)

It evolved in South America and stayed there instead of heading into Central and North America. Some experts think it shared the continent with Gracilis, with the Andes as a dividing line. (San Diego Zoo)

Using a mountain chain as a territorial marker seems less strange when you realize that Populator was almost 4 feet high at the shoulder and weighed over 800 pounds. (Antón)

Compare the size of its tracks in this video with the human shown near it.

This was a behemoth!

But as scary as Smilodon cats must have been, something terribly beautiful left the world when they finally disappeared.

 


Featured image: Smilodon populator. Cope, E. D. 1880. On the extinct cats of America. American Naturalist. xiv (12):833-857, figure 12.

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

San Diego Zoo. 2009. Saber-toothed cat Smilodon fatalis. http://library.sandiegozoo.org/factsheets/_extinct/smilodon/smilodon.htm Accessed August 15, 2017.

Wallace, S. C., and Hulbert, Jr., R. C. 2013. A new machairodont from the Palmetto Fauna (Early Pliocene) of Florida, with comments on the origin of the Smilodontini (Mammalia, Carnivora, Felidae). PLoS ONE. 8(3): e56173.