Book Preview: Fact #18. The cat-dog split goes almost all the way back to the K/T (K/Pg) extinction.

Cats and dogs are with us today; that is, they’re domesticated animal members of the human family.

But they are also predators by nature, just like their wild relatives, which include but aren’t limited to lions, tigers, wolves, and bears.

These particular members of the order Carnivora all have claws, fangs, and powerful hunting instincts, but a few others get by without such tools. This is why biologists trying to classify animals look for a set of specialized meat-slicing teeth (called carnassials) that all carnivorans have.

That’s just step #1. The boffins then must file each of the world’s 280-plus carnivoran species (and over 350 fossil groups) into one of Carnivora’s two natural suborders: feliform and caniform.

“Form” here doesn’t refer to the animal’s outward appearance. It involves some dental features as well as certain cranial structures around the ear and skull base that only a zoologist or paleontologist could love.

These anatomical details are all one way in cats and other feliforms and all another way in caniforms, including dogs.

Scientists don’t understand why such a difference exists. But they do know that it has been around for more than 60 million years.

Do cats and dogs go back to the K/T extinction?

Short answer: No, but Carnivora probably does (its origin story isn’t completely known yet). However, while early small, weasel-like carnivorans already had some feliform/caniform distinctions, they had to play second-fiddle to a group of apex predators called creodonts for tens of millions of years.

Details: Today, Feliformia includes hyenas, oddly enough, as well as civets, meerkats and other mongooses, Asiatic linsangs, and a few other groups in addition to the cat family Felidae.

A young Asiatic linsang:

Caniforms other than dogs include, but aren’t limited to, bears, raccoons, skunks, weasels, foxes, otters, badgers, and (believe it or not) seals and walruses.

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Guest Video: Tumbler Ridge, British Columbia

There will come a point in this drone video, made in the UNESCO Tumbler Ridge Geopark, when you will wonder where the dinosaurs came from. Here you go.

Seriously, look at those flat rock formations: that’s all undisturbed sedimentary rocks that have accumulated over a vast amount of geologic time. Of course there are fossils in there! (Bonus points if you can spot the cirques; here’s more geological background.)

Here’s a bit more about the dinosaurs. To show how far out in the wilderness this geopark is, note the hope expressed that they won’t need much helicopter support:

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A Very Addictive Online Dinosaur Site

Between working on the ebook and keeping up with Kilauea (see “live” blog link in upper right corner of the page), I can only put up some guest videos to thank people for coming here.

However, I found this site, first with the interactive globe that shows what position the continents were in down through geologic time.

For example, you have heard that a big asteroid hit the Yucatan 65 million years ago and caused a mass extinction, right? And you picture an impact on modern-day Mexico.

But the continents were arranged somewhat differently back in the day:

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George Gaylord Simpson

One day, someone who had dropped by saw me reading a book and asked what it was about.

“Evolution,” I replied.

“Oh, Darwin!”

“No, Simpson.”

” . . . ”

We moved on to other topics. It’s hard for a layperson like me to explain who Simpson was and why evolutionists do rank him, and a few other 20th-century researchers, right up there with Charles Darwin.

Nevertheless, I must describe how Simpson made it possible for me to start work on this ebook series.

Like everyone else, I had the general picture linking Charles Darwin with evolution. We don’t often think about the details, but I had the idea a few years ago of writing an ebook about how cats evolved.

To do this, I first had to check up on how evolution has progressed since Darwin’s time. Gah!


Evolution, apparently. (Source)

That’s one of the more extreme examples, and I don’t know how widely this particular paper is accepted. Reportedly, it was a breakthrough.

Nevertheless, most papers I checked to learn more about the evolutionary mechanisms that shaped today’s cat family did involve math as well as a mysterious concept called an “adaptive landscape.”

Whatever happened to natural selection and the survival of the fittest?

The short answer is, genetics.

Darwin came before this 20th-century scientific field existed. All of his discoveries had to be reinterpreted through newly discovered genetic insights. The details of this work, and Simpson’s role in it, are described here.

If you visited that link, you saw that it was the preface to a collection of papers honoring the 50th anniversary of a book you have probably never heard of called Tempo and Mode in Evolution.

Simpson published it in the 1940s, with the help of family and friends, while he was off somewhere fighting WWII.

It’s a literary masterwork for its concise and clear presentation of complex information, especially if you know the background, which I didn’t at that point beyond noting as I read that, while the writer respected some people named Wright and Dobzhansky, he had his own take on things.

Scientifically, it rocked the world.

G. G. Simpson described in easy-to-read and ordinary English a way to use genetics and math to graph out evolutionary processes. The way he described it, for example, it was clear to me how and why prehistoric horses switched over from browsing on leaves to grazing grass, because it was just a matter of two graphs overlapping, sort of.


Simpson used a couple of simply U-graphs on an X-Y axis. Things have progressed over the years. (Source, CC BY 2.0)

All this sounded like what little I had found thus far on adaptive landscapes, but I never saw the term in that book. I did not realize then that Simpson basically invented the concept with Tempo and Mode in Evolution.

He was among the very few people in human history to use math to model the real world successfully, enabling lots of progress. And he did it without computers, during World War II, using short, simple words and sentences that even a layperson can follow.

Thanks to Simpson, I can now understand the evolution of cats a little bit better.

G. G. Simpson biography (Wikipedia)

George Gaylord Simpson: Natural Selection and the Fossil Record. (PBS)

Featured image: Source.

“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?

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.




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. 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. . Last accessed December 11, 2015.

Hulbert, Jr., R. C., and Valdes, N. 2015. Smilodon fatalis. Florida Museum, University of Florida. 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.