Category Archives: Where Cats Come From

Housecats and Wildcats (Fluffy and Silvester)

Ever wondered if different kinds of housecat – like a tabby and a Persian, or street cats and purebreds – are different species?

Biologists say that these animals all have the same formal last name (for species or subspecies) – catus.

So it’s all one group despite appearances or lifestyle.

The biologists then politely excuse themselves and get back to work, because the real challenge is telling housecats and wildcats apart, and they’re working under a wildcat conservation deadline.

What’s a wildcat?

Well, it’s not that beautiful animal at the top of this post. That is a housecat – a pedigreed Norwegian forest cat, in fact. It’s a catus.

Here’s a wildcat, photographed in a German national forest:

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It won’t follow you home, no matter how friendly and gentle you are. European wildcats are mostly untameable. (Sunquist and Sunquist, 2002)

The resemblance between these two particular cats is eerie!

Fluffy the Housecat and Silvester the Wildcat don’t always look that much alike. Cat fanciers have worked hard to maintain a wildcat appearance in the Norwegian fancy-breed.

It’s quite an achievement. The breeders are limited to the human time scale, while European wildcats have had hundreds of thousands of years – since roughly the middle of the Pleistocene – to develop their look. (Yamaguchi and others, 2004)

Wildcats are formally known as Felis silvestris. (It’s usually abbrevated as F. s..)

So, even though the cats above are almost mirror images, they belong in different subgroups – catus and silvestris, respectively.

Still, Nordic “twins” aside, housecats and wildcats do have a lot in common.

Flying wildcat
Spot quiz: Domestic cat, wildcat, or a new Marvel character? The bushy ringed tail, with its blunt tip, clues us in that this is a Scottish wildcat. Actually, its nickname – Highland Tiger – would make a good Marvel character name!

Fluffy and Silvester deserve their own post in this series on cat evolution because:

  • Obviously, they’re closely related. But some of the best minds on the planet can’t agree whether domestic cats and wildcats are two different species (Felis catus and Felis silvestris) or just subgroups of the same one, i.e., F. s. catus and F. s. [wildcat subspecies name]. It’s just words to us, but the uncertainty can really mess up legal efforts to protect wildcats. (Macdonald and others)
  • Our own history is part of the story. Cats have associated with human beings for at least ten thousand years. (Vigne and others, 2012) During that time, we’ve carried Fluffy all over the world. And in the last century and a half, we have also dramatically changed its appearance through a system of artificial selection called the cat fancy.
  • Housecats and wildcats interbreed so much that it’s almost impossible to find “pure” wildcats in some parts of Europe. This prompts warnings that wildcats are at risk for genetic extinction. But doesn’t interbreeding show that catus and silvestris are the same species? And how can having kittens make the parents go extinct? The biologists are working on these and other questions.

Let’s start off with the cats closest to us – the few that are fancy-breeds as well as the many unpedigreed domestic cats that share our homes, yards, and streets.

Then we will get a little better acquainted with Silvester and see how some wildcats might have been domesticated.

After a brief outline of Fluffy’s history, we’ll check out the issue of genetic extinction – what it is and what it could mean for people – especially cat owners – as well as wildcats.

Feral cats, fancy breeds, and housecats

You aren’t imagining things – there really are a lot of cats out there, 600 million of them associated with households and another 600 million unowned, roaming and reproducing freely (Driscoll and others, 2011), i.e., feral cats. (Robertson)

“Feral” does mean “wild,” but these aren’t wildcats. Wildcats are, well, wild – feral cats were once domestic or else have very close relatives that are domesticated.

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Some cats haunt the borderland between feral and domestic.

Feral cats exist wherever people live or have lived. It’s a worldwide problem, and one that we humans have caused. (Robertson)

But in this post they are only relevant to the wildcat conservation issue, so we’ll talk about feral cats later.

What about the hundreds of millions of owned cats? Who really owns whom?

In other words, are housecats really domesticated?
Continue reading Housecats and Wildcats (Fluffy and Silvester)

All the Cats in the World Except Fluffy and Silvester

It’s enormous fun to look at cat evolution, because you get to look at cats. Even people who don’t like pet cats are impressed by cheetahs, lions, and tigers.

Cheetah dramatic
How did life on Earth come up with something like this . . . and housecats and lions, too?

There are actually more cats out in the wild than most of us have ever dreamed of, including the gorgeous Asiatic golden cat shown at the top of this post.

Today we are going to look at all of them, except for Fluffy and its wildcat relatives. I’m saving them until next time for two reasons:

  • The biological line between housecats and their ancestors – the wildcats (one word) – is blurry, so we need to check them out all together.
  • We do need to talk about how cats evolved. Even though that happened to wild cats (two words) over millions of years, Fluffy’s history is helpful. Cat breeders have been intentionally messing with its genes for over a century. Is the process that has given us the tailless Manx and the bald Donskoy typical of all evolution? Tune in next time and find out!
Evolution of catcher(0)
Evolution would be great fun, too, if it worked like this. Sadly, it doesn’t, unless evolution is a lot weirder than experts think – and that’s very weird. Cats continue to play with toys and humans still must work their way through the bush leagues for a chance to play in The Show.

The following eight sections are based on the eight genetic lineages that DNA sequencing consistently shows in the cat family. (Johnson and others, 2006; Nyakatura and Bininda-Emonds)

They aren’t presented in the order in which each group evolved – those dates come out differently for different researchers. So far, I think, the only consensus is that there are eight lineages.

The pictures have all been generously donated to either Creative Commons or the public domain by many generous photographers.  Be sure to check out their links in the image credits at the end of this post!

Let’s start out with the lineage that contains the cat featured at the top of this post – the Asiatic golden cat, known locally as the “fire tiger.” (Sunquist and Sunquist, 2002)

Then we’ll check out the big cats and the other six lineages.
Continue reading All the Cats in the World Except Fluffy and Silvester

The Evolution of Cats: 6: Nimravides and the Metailurini

It’s time to look at “the other sabertooths.”

Some of them are also called “false sabertooths.” (Antón)

Whether false or true, these now-extinct animals are giving scientists useful insights into the world of sabertoothed cats.

You probably haven’t heard of them.

Everybody knows Smilodon – the California state fossil and star of Ice Age. Quite a few laypeople recognize the name of Homotherium, too.

homotherium-profile
Homotherium’s teeth weren’t as long as Smilodon’s and it had a lighter build.

We met both of these and other popular sabertoothed cats last time.

But hardly anyone outside the Paleontology Department’s “cat” section has ever heard of Nimravides or the Metailurini.

As one 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)

When talking about fossil cats, paleontologists still have many “grave reservations” to overcome.

Very few of those issues came up last time, when we checked out the Homotheriini and the Smilodontini.

smilodon-cope
Smilodon, as the 19th century saw it.  This fossil sabertooth is still wildly popular in the 21st century.

Those sabertooths get a lot of attention from the public as well as researchers, and paleontologists have researched them in great detail. (Werdelin and others)
However, the two tribes weren’t the only toothy big cats around during the Miocene epoch and the Plio-Pleistocene ice ages.

No history of feline evolution is complete without mention of:

  • Nimravides. Long-legged and the size of a modern lion (Hunt, 2004), this was a mysterious North American saber-cat.
  • The Metailurini. Part sabertooth, part “normal” cat, these predators 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 is nowhere near as charismatic as Smilodon, but scientists are very curious about this cougar-like Miocene cat.  Was it a sabertooth or not?

 

Aside from the occasional complete skeleton, most of the other sabertooth fossils are fragments that can be interpreted in different ways. (Turner and Antón)

Of course this leads to lots of scientific controversy.

Yet the basic facts about Nimravides and the Metailurini are clear enough.

Both cat groups developed around the same time as the early members of the Homotheriini and Smilodontini. Then they coexisted with the two tribes for millions of years.

Nimravides didn’t make it out of the Miocene epoch (Werdelin and others), but the last member of the Metailurini died relatively recently, during the second half of the Pleistocene. (Werdelin and Dehghani)

All of them were very successful predators, and here is their story, as far as researchers have been able to outline it to date.

Continue reading The Evolution of Cats: 6: Nimravides and the Metailurini

The Evolution of Cats: 5. Sabertooths, Part 1

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

We should be celebrating that fact. Instead, we have forgotten the terror that these ferocious animals inspired in our ancestors.

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 LINK, safety could not be guaranteed in the saber-cat enclosure.

Nobody knows how these extinct animals behaved.

Some of them 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?

Saberteeth

All cats are hypercarnivores. That’s 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, upper fangs are rather cone-shaped – thick at the base and tapering up into a 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. In contrast, all modern cats use a stalk-and-pounce hunting technique. (Werdelin, 1989)

Paleontologists say that there are 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.  

Per Antón, the species name “necator” isn’t used any more.

These subtle differences matter a lot to experts. That’s why you’ll often see “dirk-tooth” or “scimitar-tooth” on the Web or in books about sabertoothed cats.

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

Sabertooths down through time


These specialized upper canine teeth 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)

All four, plus the very first sabertooths – those Permian gorgonopsids we met last time – 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 Evolution of Cats: 5. Sabertooths, Part 1

 The Evolution of Cats:  4.  The First Cat

Last time, Silvester the African wildcat showed how our own housecat would live out in the wild . . . as long as the habitat was a place like the Kalahari plain in southern Africa.

Fluffy’s style would have to change if it lived in a swampy jungle or high up in the Andes.

Yes, there are small cats in the Andes. Andean mountain cats are rare and hard to study. (Sunquist and Sunquist)

Felids (members of the cat family Felidae) are up to the challenge. These very adaptable animals are found all over the world today.

They are also in the geologic record. For tens of millions of years cats have always:

  • Competed with each other in all these places
  • Hunted prey that was evolving rapidly and in diverse ways
  • Had sex and raised kittens
  • Coped as best they could with other community predators that ranged from prehistoric giant beardogs; through the very cat-like ancient nimravids and barbourofelids that we will meet next time; to today’s Homo sapiens.

That’s a lot of work. No wonder modern cats tend to be a little irritable!

This jaguar looks a little like the Joker!

Those interactions with the environment and with other living members of their communities have, of course, influenced the evolution of cats in many ways.

We need this broader post now to move beyond Silvester and take a very general look at how the first cats evolved.

Then, next time, we can meet some of them, starting with the sabertooths.

Now, ladies and gentleman, set aside some time for reading – this post does cover a central idea in my book, that the evolution of cats was an epic  – and step this way into the time machine . . .

(Mind the gorgon, the T. rex, and the angry quoll.)

Humble beginnings

Many of the complex feline features that we admire today actually evolved to meet a vital but simple need in the past.

Sometimes this need arose a very long time ago.

Believe it or not, a cat’s beautiful coat; its claws, whiskers, and teeth; and the glands it uses to advertise for a mate and to mark its territory all come from integument (Chuong and Harberger) – that is, from skin.

Cats are still recuperating from the evolutionary effort.

Integument first evolved in some of the oldest ancestors of mammals and reptiles.

Those former fish needed the outer covering to protect themselves from dehydration, now that they were spending more and more time out of the water.  (Alibardi)

Integument of various shapes and qualities also helped them slither around or pull themselves along as they colonized the land.  (Alibardi)

Today, molecular biologists say that things like claws and teeth come from the integument’s epithelial stem cells.

These cells can be organized in lots of different ways.  (Chuong and Harberger)

Exactly how this works isn’t well understood yet, but it has indeed led to the diversity of today’s animals. (Chuong and Harberger)

The development of integument is one of the points where the story of cat evolution (and much else) really begins.

We need to go back 350 million years for it (Benton and others) – a much longer span of time than the 65 million years or so that have passed since the K/T extinction of nonavian dinosaurs and some other forms of Cretaceous life.

A modern avian dinosaur poses with data from the geological record. Feathers developed from integument, too. (Chuong and Harberger)

We would have needed a time machine anyway.  Cats are mammals, after all, and the Linnean order Mammalia is very old.

You might have heard that the Age of Mammals began when nonavian dinosaurs went away.

Actually, that’s just the Cenozoic – sixty-five million years of what scientists who take the really long view call “recent life.”

Mammal beginnings are nowhere near as recent as that.

Mammals and dinosaurs

Two-thirds of the real Age of Mammals was already over (Kielan-Jaworowska) when a killer bolide suddenly appeared in Cretaceous skies.
Continue reading  The Evolution of Cats:  4.  The First Cat

The Evolution of Cats: 3.  Fluffy’s African Granddaddy

As we saw last time, laypeople have a lot of questions about Fluffy the housecat and where this quirky little animal and its relatives fit into our shared Universe.

There are still many blanks in the scientific puzzle that’s the evolution of cats, but specialists in everything from paleontology to genetics are fitting quite a few of the pieces together.

Blog posts here and eventually the book Where Cats Come From describe what I understand those experts to be saying about their work.

The easiest way to begin is by looking at Fluffy.  Housecats are built and act the same as the big cats, and they’re a lot more convenient to use as models.  (Turner and Antón)

However, this approach has its limits because ten thousand years of domestication (Clutton-Brock; Driscoll and others; O’Brien and others) and a century and a half of the cat fancy have reshaped the housecat right down to its genes.

We need to get a little more wild if we’re going to look at the evolution of all cats, including the big ones.

Let’s leave Fluffy in the house for now and visit its nearest ancestor, the African wildcat. (Driscoll and others; O’Brien and others)

Introducing Silvester

There are a lot more small cat species out there than most of us realize, but many people in Europe, Africa, and the Middle/Near East probably have heard of the group called wildcats.
These aren’t bobcats or other medium-sized or small cats.  As you can see up above, wildcats actually look a lot like housecats.

That resemblance is not a coincidence.

Continue reading The Evolution of Cats: 3.  Fluffy’s African Granddaddy

The Evolution of Cats:  2. Where Do Cats Come From? An introduction.

The world of felines is beautiful, varied, sometimes dangerous, and always mysterious.  Many of us are attracted to this world and we wonder how cats evolved.

Here are a few common questions and brief answers:

Q:  Are humans responsible for turning other cats into housecats?  

A:  No.  Registered cat breeds aren’t the same things as species.  And domestication has only happened to one modern cat species: Felis s. catus, the housecat. In the past, people did domesticate some individuals of other species, like the cheetah and the jungle cat, but that didn’t catch on the way it has with Fluffy.

Q:  Even if we had nothing to do with it, how are cats such as, say, a jaguar and a Siamese related and why are they so different?  

A:  They’re related in lots of ways.  The exact answers here depend on how far back you want to go.  One reason they are different is that the cat family line that led to the jaguar is older than the line that led to Fluffy.  (O’Brien and Johnson)  Experts are still working out these and other details with molecular studies as well as fossils

Q:  Where does the sabertoothed tiger fit in?  

A:  There never was such a critter. Seriously.  See van den Hoek Ostende and others, referenced at the end of this post. All modern cats are cousins of Smilodon and the other true sabertoothed cats, but they are not direct descendants of the sabertooths.  (Antón; Werdelin and others)

These answers only skim the surface, of course, but that’s how it is with most quick looks at where cats come from.  

It’s hard to find a fairly complete yet simple story about what scientists know of the evolution of cats.  That is why I am writing a book about it, as well as practicing with these blog posts.

I have read research papers and books, like those listed below, in a variety of related fields and have learned that cat evolution is a hot topic.  

No wonder knowledgeable discussions about it can get very sciencey very quickly!

Wayne and others (again, see source list at end of this post) are right when they say that scientists have a “. . . special fascination . . . for cultural, aesthetic, and scientific aspects  of the cat family.”

There’s a practical aspect as well.  Cat genetic studies have “applications ranging from disease gene discovery . . . to species conservation.”  (O’Brien and others)

That’s nice.

But the rest of us cat lovers don’t commune with Nature at such rarefied heights.  

We just enjoy Fluffy and watch documentaries or go on safaris and to zoos to see some big cats.  

Just like the scientists, we wonder how cats evolved, but we would like to hear more about it in plain English.

The problem is, evolution is a complicated topic.  So are cats.
So is environmental history over geologic time – Earth hasn’t always been like it is today.  

The scientific method is pretty tough, too.  As J. A. Van Couvering puts it,  

[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.

Put all this together and . . . well!

And yet . . . holding a purring housecat is one of the simplest and finest things in the world.  It’s a little like holding Nature’s heart next to yours.  

So we laypeople do ask about this little animal and where it and all of its relatives fit into our shared Universe.

I’m going to write down all that I have learned about answers to my own questions, and perhaps you will find that helpful, too.  Also be sure to check out the references at the bottom of each post; these may help you even more.

The next post in this series will take a detailed look at the housecat’s nearest ancestor, African wildcats. (Driscoll and others; O’Brien and others)

African wildcats are a lot like Fluffy, not surprisingly.

I hope you will enjoy this series on cat evolution as much as I am enjoying writing it!


IMAGES:

Feature image:  Rama:  Hoplophoneus primevus.   Edited by Robin H.  Happy Halloween!  CC BY-SA 2.0.  http://en.wikipedia.org/wiki/Hoplophoneus#/media/File:Hoplophoneus_primevus_IMG_4443.jpg

Sonelle:  African Wild Cat at the Johannesburg Zoo, South Africa. Originally uploaded to English Wikipedia (21:57, 25 January 2005) {{GFDL}}


CITED AND UNCITED REFERENCES:
AZA Lion Species Survival Plan (2012).  Lion Care Manual.  Association of Zoos and Aquariums, Silver Spring, Maryland, p. 143.

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.

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. 

Burgess, S. D.; Bowring, S.; and Shen, S.  2014.  High-precision timeline for Earth’s most severe extinction.  Proceedings of the National Academy of Sciences.  111(9):3316-3321.

Clutton-Brock, J.  1989.  Competitors, companions, status symbols, or pests:  a review of human associations with other carnivores, in Carnivore Behavior, Ecology, and Evolution, ed. Gittleman, J. L., 2:375-392.  Ithaca, NY: Cornell University Press.

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.

Francis, J. E., Marenssi, S., Levy, R., Hambrey, M., Thorn, V. T., Mohr, B., Brinkhuis, H., Warnaar, J., Zachos, J., Bohaty, S., and DeConto, R.  2009.  From Greenhouse to Icehouse: The Eocene/Oligocene in Antarctica, in Developments in Earth  and Environmental Sciences, ed. Florindo, F. and Siegert, M., 311-372.

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

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.

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

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. 

Van Couvering, J. A.  1984.  Introduction to Catastrophes and Earth History:  The New Uniformitarianism, ed. Berggren, W.A. and Van Couvering, J.A.  Princeton:  Princeton University Press.  

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.

Wayne, R. K., Benveniste, R. E.,  Janczewski, D. N., and O’Brien, S. J.  1989.  Molecular and Biochemical Evolution of the Carnivora, in Carnivore Behavior, Ecology, and Evolution, ed. Gittleman, J. L., 1:465-494.  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.