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.

A noteworthy distinction of feliforms is that they all are missing the upper and lower third molar teeth, compared to caniforms. This matters because 63-million-year-old fossils have been found with the same dental gap.

It’s hard to say much more than that–the fossil record from that long ago just isn’t very good. What few bones and teeth have been found are scattered and in fragments.

It would help us understand how far back caniforms and feliforms go if we knew how the order Carnivora evolved.

That’s still a mystery, but enough fossils have survived (at least in North America, which has the most complete geological record of those times) to make two different scenarios:

  1. A tiny Cretaceous mammal called Cimolestes could be the founder. It survived the K/T (K/Pg) extinction, so if this is true, carnivorans go all the way back to the dinosaurs. Unfortunately, no one knows if Cimolestes was a placental mammal, like carnivorans, or something else, like a marsupial.
  2. Small predators called miacids, in the early Age of Mammals, were the founders. The problem here is that miacids aren’t well understood, either. Still, it was a 63-million-year-old miacid that had that feliform dental pattern. And Flynn and Galiano (see source list below) suggest a link between caniforms and what they call “miacine” miacids.

It looks like feliforms and caniforms go back almost all the way to the K/T (K/Pg) extinction. However, they weren’t apex predators back then, as carnivorans usually are today.

Another group of placental predators, called creodonts, made it to the top first. They stayed there a long time, too, dominating things for almost the entire first half of the Age of Mammals.

For all that time, carnivorans stayed small and slinky. Then, around 30 million years ago, something changed. No one knows exactly what happened between the two groups, but creodonts went into a decline and carnivorans took over.

What does all this ancient stuff about long-extinct animals have to do with us today?

It’s a major reason why we now have dogs and cats.

How did cats and dogs evolve?

Short answer: This is a hot research topic and difficult for the writer, who is a layperson, to follow. Let’s keep it short to cut down on errors.

As far as dogs go, per Wang and Tedford (see source list below):

  • Prohesperocyon wilsonii, the first clearly identified member of the dog family, lived in what’s now Texas about 40 million years ago. That’s around the middle of the Eocene, if you’re keeping track of geologic epochs.
  • Three major groups are descended from Prohesperocyon. The one we’re interested in–Caninae–kept a low profile through the late Eocene, all of the Oligocene, and much of the Miocene as each of the other two groups had its heyday and then faded away.
  • In the late Miocene, it was Caninae’s turn. This group is still around today. Its subgroup Canis, which now includes coyotes, jackals and some wolves, along with dogs, showed up around 6 million years ago.
  • Canis lupus, the gray wolf, arrived about 1 million years ago, in the Pleistocene. Some members of this species met people and became the first dogs.

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Kristine Paulus, CC BY 2.0


The cat fossil record is harder to interpret, say paleontologists, because cat skeletons past and present all resemble each other. Convergent evolution–different species evolving in similar ways–makes things even tougher.

Here is a general overview of how cats evolved, from three sources: Flynn and Galiano; Salesa and others; and Werdelin and others:

  • Molecular studies suggest that the modern cat family first appeared around 34 million years ago.
  • Proailurus, the “Dawn Cat,” arrived in Europe around 22 million years ago.
  • A group of cats, known collectively as Pseudaelurus, came next. Current thinking is that, in the late Miocene (about 12 million years ago), one leopard-sized species evolved into the sabercats. Smaller ones–often called Styriofelis instead of Pseudaelurus–were ancestors of the modern cats.
  • Soon after that, around 11 million years ago, the big cat lineage developed. Over the next six million years or so–i.e., quickly, in evolutionary terms–the other modern lines developed.
  • Today’s Felis cats (house cat, wildcat, sand cat, black-footed cat, and jungle cat) last shared a common ancestor a little over 3 million years ago.
  • Around 10,000 years ago, right after the last ice age, wildcats were domesticated in the Fertile Crescent.

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Trish Hamme, CC BY 2.0


We seldom realize it, but our pets are living links not only to their wild relatives but also to a rich history that extends all the way down to the start of the Age of Mammals (and perhaps even back into dinosaur days).


Featured image: JACLOU-DL at Pixabay.


Sources:

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

Barycka, E. 2007. Evolution and systematics of the feliform Carnivora. Mammalian Biology. 72(5):257-282.

Driscoll, C. A.; Menotti-Raymond, M.; Roca, A. I.; Hupe, K.; and others. 2007. The Near Eastern origin of cat domestication. Science. 317:519-522.

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.

Meloro, C.; Clauss, M. and Raia, P. 2015. Ecomorphology of Carnivora challenges convergent evolution. Organisms Diversity & Evolution, 15(4): 711-720.

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.

Prothero, D. R. 2006. After the Dinosaurs: The Age of Mammals. Bloomington and Indianapolis: Indiana University Press. Retrieved from https://play.google.com/store/books/details?id=Qh82IW-HHWAC

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.

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

Wang, X., and Tedford, R. H. 2008. How dogs came to run the world. Natural History, 117: 18-23.

Werdelin, L., and Turner, A. 1996. Turnover in the guild of larger carnivores in Eurasia across the Miocene-Pliocene boundary. Acta zoologica cracoviensia. 39(1):585-592.

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, eds. Macdonald, D. W., and Loveridge, A. J., 59-82. Oxford: Oxford University Press.

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

Wikipedia. 2018. Caniformia. https://en.wikipedia.org/wiki/Caniformia Last accessed August 9, 2018.

Wikipedia. 2018. Carnivora. https://en.wikipedia.org/wiki/Carnivora Last accessed August 9, 2018.

Wikipedia. 2018. Feliformia. https://en.wikipedia.org/wiki/Feliformia Last accessed August 9, 2018.

Wozencraft, W. C. 1989. The phylogeny of the recent Carnivora, in Carnivore Behavior, Ecology, and Evolution, ed, Gittleman, J. L., 495-535. Springer: Boston.


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