Thylacoleo carnifex, ancient Australia’s marsupial lion

31 08 2007

My home state of New Jersey is the epitome of suburban sprawl, McMansions and cul de sacs being about as common as the White-Tailed Deer that take advantage of the grass and brush on the side of the Garden State Parkway year round. There is seemingly no place you can go in the state where the rumble and roar of traffic cannot be heard, although the sprawling network of impervious surface does allow for easy travel to almost anywhere in the “Garden State.” On these roads, usually on warm summer nights, you’re likely to see what appears to be a large white rat shuffling across the lanes. While there are no hackneyed jokes that I know of about the Virginia Opossum crossing the road (“To eat your garbage” would be the most realistic answer), the critters turn up as roadkill quite often, not a very dignified end for the only marsupial mammal to live north of the Rio Grande in North America. While the scruffy Virginia Opossum represents the whole of marsupial mammals in the U.S., it has many close relatives throughout South America (Order Didelphimorphia), and is a bit more distantly related (but still close) to the Australian “possums” (Suborder Phalangeriformes), the marsupial forms of “the island continent” being perhaps the most familiar and oddly charismatic of any members of the Infraclass Marsupialia.

A Red Kangaroo (Macropus rufus) at the Philadelphia Zoo (taken in February, 2007). The Red Kangaroo is probably the world’s most recognizable living marsupial mammal.

Much like any group of living mammals, however, the fossil record of marsupial mammals is full of bizarre forms that have left no living descendants. We should not regard such lines of extinct fauna as somehow inferior or flawed, however. As famed paleontologist Stephen Jay Gould once wrote in his book Wonderful Life;

First, in an error that I call “life’s little joke”, we are virtually compelled to the stunning mistake of citing unsuccessful lineages as classic “textbook cases” of “evolution.” We do this because we try to extract a single line of advance from the true topology of copious branching. In this misguided effort, we are inevitably drawn to bushes so near the brink of total annihilation that they retain only one surviving twig. We then view this twig as the acme of upward achievement, rather than the probable last gasp of richer ancestry.

I can scarcely think of a better example of this notion of the spectacular diversity of past life than the extinct marsupial Australian Megafauna, and the carnivorous Thylacoleo carnifex would remind any fossilist that just because an animal is extinct, such status does not imply that it was not a terror in its heyday. Deemed the “Marsupial Lion” Thylacoleo carnifex developed many of the predatory adaptations we seen in living big cats (hence the “leo”, meaning “lion”, in the genus name), and despite the superficially rodent-like appearance of it’s front teeth, it was certainly a powerful predator.

In order to understand why Thylacoleo was such a formidably hunter we first need to understand something about living Carnivora (civets, otters, cats, dogs, bears, etc.) and the way their teeth were arranged. While their have been many large carnivorous mammals since in the past 65 million years, carnivores are set apart by their carnissal, or “scissor”, teeth. If we look at the massive skull of the predatory mesonychid Andrewsarchus of the Eocene, for example, the front teeth appear useful for piercing but the teeth further back in the jaw a large and a bit blunted. While useful in tearing flesh from bone and crushing, they were not especially well-adapted to cutting slicing flesh and such creatures probably ate a fair amount of bone (and possibly had problems with bone splinters in their gastrointestinal tracts) as well.

The only known skull of Andrewsarchus, on display at the American Museum of Natural History in New York City. Note the large, blunted teeth towards the back of the jaw.

The likely ancestors of today’s extant carnivores had their start long before Andrewsarchus was roaming what is present-day Asia. Miacids were weasel-like mammals and are known from the Paleocene and Eocene epochs, and are the first mammal group known to have teeth called “carnissals.” These are the teeth that group all living carnivores together, robust and pointed teeth that seem to be essential to consuming flesh. Another group of mammals, the creodonts (the first of which were discovered by E.D. Cope), also possessed carnissal teeth, but their line died out about 8 million years before the present. Still, the success of the carnivorous mammals seemed to depend on the specialization of the some of the premolar and molar teeth into a sharp, cutting edge, commiting many of the group to a strictly carnivorous lifestyle. Cats are the most specialized today, as they have lost some teeth in the front of their jaw in order to allow their dagger-like canines to have the maximum effectiveness and they no longer have flattened molars at the back of their jaw like canids (dogs) have, allowing those animals a little bit more of a diverse diet in tough times. Indeed, overspecialization in a predatory niche, called “hypercarnivory,” can often put a species at risk if they cannot effectively process other food sources if prey stocks dwindle (such a hypothesis has been put forward about the recent “bone-crunching wolf” discovered in Alaska).

A replica of the skull of Thylacoleo, on display at the American Museum of Natural History.

Thylacoleo, however, was an entirely different branch of the mammalian tree, but it seems that its skull and jaws were adapted to similar ends (although arguably were more extreme in their modifications). As easily seen from the skull of Thylacoleo, this marsupial predator was adapted to have it’s own fearsome shearing teeth. The premolars essentially became laterally-compressed blades, more high-ridged and pointed at the front, yet still sharp all the way down their length. These teeth in the upper and lower jaw even helped to sharpen each other as they slid past, allowed the predator to retain a sharp edge. Flattened teeth that might be useful for grinding or processing other foods are entirely absent behind the premolars, showing the Thylacoleo was a specialist of the highest order, having much more scissor-like teeth than the placental carnivores on other continents. Such a gape would have been absolutely fearsome, as exemplified by this recent reconstruction by Jeanette Muirhead;

Thylacoleo carnifex, used with permission of artist Jeanette Muirhead.

What is even more surprising than the blade-like teeth of Thylacoleo, however, is how strong its jaws were for a creature of its size. A recent study by Wroe, McHenry, and Thomason found that Thylacoleo, a predator that was less than four-feet long and probably weighed only 220 pounds, had the a bite force equivalent to a modern lion twice its size. The unusual dental arrangement of its jaw might have mitigated this somewhat and technical trials still have to be carried out, but if what the researchers found holds then Thylacoleo could probably have preyed upon most animals living in its range up to sub-adult size on its own, perhaps being the fiercest mammalian predator ever known.

How did Thylacoleo attain such high bite forces? The answer might have to do with the brain and skull differences between marsupials and placental mammals. Many carnivores have relatively large brains in comparison with marsupials, lessening the amount of bone they can devote to massive muscle attachments to enhance bite force. Thylacoleo, by contrast, seems to have had stronger muscle attachments and a smaller brain, and it’s skull superficially resembles that of a big cat. While canids often have elongated skulls, cats have foreshortened ones, and oddly enough Wrote and his colleagues seem to have found that carnivorous mammals that are known to be bone crunchers (primarily dogs or dog-like carnivores) appeared to have overall weaker bite forces than those that did not have the same osteophagous tendencies. This may have to do with the actual killing of prey, big cats and similarly-designed predators depending on strong bite forces in order to choke their prey to death or tear out a large chunk of the prey’s neck with a jugular bite. There are exceptions to this, the bite of saber-toothed cats often being calculated as relatively weak, but overall it seems that a shorter skull with a deep mouth is better of achieving high bite forces than a longer and narrower one. Hence, Thylacoleo actually is not a bad name for the “pouched lion”; it seems to share a large amount of convergences with its modern-day namesake, although it may have been less bright (and less sociable) with a more powerful bite.

Ventral view of the skull of Thylacoleo. From E.D. Cope’s “The Tertiary Marsupialia” in The American Naturalist, Vol. 18, No. 7. (Jul., 1884), pp. 686-697.

The predatory affinities of this animal did not always seem so obvious, however. Paleontologist E.D. Cope, in a paper entitled “The Tertiary Marsupiala,” recaps some of the controversy about the feeding habits of Thylacoleo that formed in the late 1800′s;

The discussion between Professor Owen on the one side, and Messrs. Falconer, Krefft and Flower on the other, as to the nature of the food of Thylacoleo, is known to paleontologists. From the form of the teeth alone, Professor Owen inferred the carnivorous nature of the food of this genus, while his opponents inferred a herbivorous diet from the resemblance between the dentition and that of the herbivorous Hypsiprymnus. I have pointed out that the comparison of Thylacoleo with Hypsiprirnnus is weakened by two considerations :

First, the cutting teeth in the two genera are not homologous ; second, the grinding series of molars, complete in Hypsiprymnus, is almost wanting in Thylacoleo. It evidently does not follow that because Hypsiprymnus is herbivorous Thylacoleo is so also. Professor Flower refers to the reduction of the molars in Thylacoleo as slightly complicating the problem, and concludes that the food of that animal may have been fruit or juicy roots, or even meat. It is difficult to imagine what kind of vegetable food could have been appropriated by such a dentition as that of Ptilodus and Thylacoleo. The sharp, thin, serrate or smooth edges are adapted for making cuts and dividing food into pieces. That these pieces were swallowed whole is indicated by the small size and weak structure of the molar teeth, which are not adapted for crushing or grinding anything but very small and soft bodies. It is not necessary to suppose that the dentition was used on the same kind of food in the large and the small species… In Thylacoleo carnifex it might have been larger eggs, as those of the crocodiles, or even the weaker living animals. The objection to the supposition that the food consisted of vegetables, is found in the necessity of swallowing the pieces without mastication. In case it should have been of a vegetable character the peculiar premolar teeth would cut off pieces of fruits and other soft parts as suggested by Professor Flower, but that these genera could have been herbivorous in the manner of the existing kangaroos, with their full series of molars in both jaws, is clearly an inadmissible supposition.

I have to agree with Cope; it is hard to imagine what sort of vegetable matter Thylacoleo would be eating with its specialized dentition. It would have been able to chop plants, surely, but whatever food was not inside the mouth would fall into the ground, that inside the mouth would have to be swallowed whole. This would results in Thylacoleo chewing much more low-quality plant food than other animals with teeth adapted to herbivory, and I doubt that Thylacoleo had a caecum or a habit of swalling smooth stones to aid in the digestion of the hypothetical greenery. Even in 1969, however, there seemed to be some doubt as to whether Thylacoleo was a herbivore, an omniovore, a carnivore, or a hypercarnivore. Leigh Van Valen, in the paper “Evolution of Dental Growth and Adaptation in Mammalian Carnivores”, wrote;

The jaw musculature of Thylacoleo was generally similar to but more powerful than that of Trichosurus, but whether all this increase was an adaptation to greater size is unknown. The question of the diet of Thylacoleo is unresolved. If Thylacoleo was carnivorous, it was in several respects a relatively inefficient carnivore. However, large carnivores were rare in Australia, and the condition of Thylacoleo is what would be expected if a Trichosurus-like phalanger became carnivorous. But the herbivorous diet advocated especially by Flower, Krefft, Lydekker, Charles Anderson, and Gregory remains a real possibility. A decision on this matter will probably not be possible until there is adequate knowledge of the appendicular skeleton.

The initial descriptions of Thylacoleo by Richard Owen were more certain of the carnivorous habits of the marsupial, however. One December 16, 1858, Owen’s paper “On the Fossil Mammals of Australia. Part I. Description of a Mutilated Skull of a Large Marsupial Carnivore (Thylacoleo carnifex, Owen), from a Calcareous Conglomerate Stratum, Eighty Miles S. W. of Melbourne, Victoria” was read before the Royal Society. It states;

The evidence of a large carnivorous marsupial, from pliocene formations in Australia, reached me not many years after my determination of the still larger herbivorous marsupial, Diprotodon australis, which first suggested the idea of the coexistence. The evidence was received in the year 1846…

The fragmentary skull of Thylacoleo from Owen’s paper “On the Fossil Mammals of Australia. Part I. …”

The initial fragmented skull of Thylacoleo carnifex (Owen), pictured above, was obtained and sent to the great naturalist by Dr. Hobson of Melbourne. Upon receiving the fossils, it seems that Owen almost immediately recognized the convergences in the skull with modern carnivores, the extant lion (Panthera leo) being his foil for the characters in the new skull. Owen describes the deterministic state and characters of the skull as follows;

The ‘skull’ consisted of the cranial part, similar in size and in the development of the temporal ridges and fossae to that of a Lion. The ‘incisor’ was a large tooth with a trenchant or incisive crown, implanted, with a small tubercular tooth, in a portion of the right superior maxillary bone, including part of the orbit and lacrymal bone. The latter specimen gave decisive confirmation of the carnivorous character of the fossil, the ‘incisor’ tooth answering in shape and function to the great sectorial or ‘carnassial’ and the tubercular tooth to the small tubercular molar of the Lion; being situated, as in that animal, on the inner side of the back part of the sectorial tooth.

Indeed, the bladelike teeth alone were enough to convince Owen of the ferocious nature such an animal must have possessed, writing;

In existing carnivorous mammals the ferocity of the species is in the ratio of the ‘carnassiality’ of the sectorial molar, i. e, of the predominance of the ‘blade’ over the ‘tubercle;’ and this ratio is shown more particularly in the upper sectorial, in which, as the tubercular part enlarges, the species becomes more of a mixed feeder, and is less devoted to the destruction of living prey. From the size and form of the carnassials of Thylacoleo, especially of the upper one, we may infer that it was one of the fellest and most destructive of predatory beasts.

A second, more complete skull of Thylacoleo carnifex, from Owen’s paper “On the Fossil Mammals of Australia. Part II. Description of an Almost Entire Skull of the Thylacoleo carnifex, Owen, from a Freshwater Deposit, Darling Downs, Queensland”

Owen’s assertions did not go unchallenged, however. In a later 1886 paper “Additional Evidence of the Affinities of the Extinct Marsupial Quadruped Thylacoleo carnifex (OWEN),” the anatomist includes a quite humorous remark in response to one of his critics. As noted before, some scientists believed that Thylacoleo was essentially a living Cuisinart specializing in cutting up fruit, no more terrifying than some of the arboreal relatives of the Virginia Opossum noted above. Owen, in classic style, writes;

These eminent authors received the support, in reference to objections to my conclusions, of the (then) Curator of the Australian Museum, Sydney, Mr. GERARD KREFFT, who, in his contribution to the ‘Annals and Magazine of Natural History,’ series 3, vol. 18, 1866, p. 148, records his opinion that “the famous marsupial Lion was not much more carnivorous than the Phalangers of the present time.”

The species of carnivorous Phalanger is not named. No evidence of such by fossil specimens has reached me, nor have I found such exceptional habit of an existing species of Phalangista elsewhere noted.

Lower jaw (outside view) of Thylacoleo carnifex, as seen in Plate I of Owen’s “Additional Evidence of the Affinities of the Extinct Marsupial Quadruped Thylacoleo carnifex (OWEN)”

Indeed, armed with a more complete lower jaw of the animal, Owen even further extrapolated its carnivorous habits, postulating that it had been the “check” on the large herbivores known from the same period in Australia. All the large forms, in Owen’s view, ceased to exist when “bimanous” forms came to the continent, either eliminating Thylacoleo or putting it out of a job through competition, although the wholesale slaughter of Australia’s megafauna by the people who would become the Aborigines is not an open and shut case. Even beyond the skull, Owen was provided with a claw complete with retractable teeth, now known to occupy the “thumb” position of this carnivore. Some have speculated that its size, ferocity, and retractable claw allowed it to climb trees like a leopard, although others have doubted this an account of how robust Thylacoleo probably was (being twice the weight of modern leopards), which 1) would have made it difficult to climb trees, and 2) would have allowed it to chase off most of the competing predators/scavengers of it’s day. I doubt that there were many creatures that would have crossed the path of Thylacoleo and survived if the “pouched lion” was hungry or territorial.

Despite it’s fearsome reputation, Thylacoleo seems to have disappeared from the land “down under” around 40,000 years ago, probably the very last of its lineage. Indeed, while I have primarily focused on Owen’s T. carnifex here, there were many other earlier species and related genera, each showing different aspects of the skull and form. Why these bizarre creatures, once so prominently disputed, have disappeared from the public understanding of paleontology I cannot say, but it is probably to the relief of living kangaroos and other Australian fauna that they are long gone.

Partial skull elements, most notably the incisors, from Owen’s paper “On the Fossil Mammals of Australia. Part IV. Dentition and Mandible of Thylacoleo carnifex, with Remarks on the Arguments for Its Herbivority”

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37 responses

1 09 2007

I found this very interesting.

1 09 2007
Christopher Taylor

You’re probably already aware that Hypsiprymnodon and Trichosurus are both actually omnivorous. Trichosurus has been relatively recently identified as a not insignificant egg predator in New Zealand. And of course, there were always the carnivorous kangaroos to contend with.

I only know Thylacoleo from reconstructions, but it’s never looked to me like something that would be a particularly agile mover on the ground. I didn’t realise just how big it was, I must admit.

1 09 2007

Thanks for the compliments and comments. I didn’t go into Hypsoprymnodon and Trichsurus because I didn’t have time to dig up enough resources by the time I was done with Thylacoleo, but perhaps I’ll cover them soon and make the connection with Owen and Cope’s remarks in this post.

It seems that Thylacoleo was overall built for power, so I have no idea how agile it would be, although (like you said) I would imagine it would be reduced. Still, I think it would be a fairly effecient predator and scavenger when possible, and it seemed to pack a lot of power into it’s relatively small frame.

1 09 2007

Nice post on one of my favourite animals. I always wondered why there were no Thylacoleo equivalents on other continents. There were so many other animals with plagiaulacoid, shear-like premolars; most multis for example, the polidolopids, the carpolestids – why non of them got bigger and more prdatory defies my imagination.

The theory that Thylacoleo was able to climb trees seems to stem from the arboreal habits of the – closely related – diprotodont possums (not to be confused with the American Opossums) and from the romantic victorian idea that the leopard attacks its prey by dropping from trees. This seems also to be the source of the popular “drop bear” myth.

The ability of dragging prey on a tree might have been useful too avoid other predators – leopards do this to save their prey from lions or hyeanas.
But, as you have mentioned, Thylacoleo was probably too robust to use the leopard as a model. Ziphodont crocs and Megalania might have been large enough too drive Thylacoleo from its prey – but they are ectothermic, and probably just too energy-efficient and not hungry enough to be more than a nuisance (on the collective level, a clash with Megalania or Quinkana might have been a disaster for an individual animal, of course).
Propleopus might have been a problem if a pack of them harrassed Thylacoleo – but I don’t know if Propleopus did indeed hunt in packs (Baboons, which seem to be the nearest ecologic equivalent to Propleopus, do not).

So the question weither Thylacoleo retained a degree of arboreality remains open. And don’t forget the worst risk connected with the “drop bear” tactic: incompetent wizzards with pointed hats….

2 09 2007

johannes…. excellent comment. You get extra points for mentioning my favorite UU “Wizzard” as well (Stibbons being a very close 2nd)

2 09 2007
Zach Miller

Ah, Thylacoleo. The freakiest of marsupial carnivores. Great post, Brian!

4 09 2007
Robert Byers

I am a creationist and am interested in the marsupial clan as I argue in a essay “Post flood Marsupial migration explained” on under authors or
I would say this marsupial lion is exactly what it is . A big cat. The “minor” differences of reproduction and and a few anatomical bits pale to all the common anatomy with other placental cats. likewise the marsupial dog, tapir, mole etc.
In responce to another poster here there is a marsupial big cat also in South America and many other marsupial kinds there now exctinct.
Creationists must explain the marsupial anomily of Australia and I am confident i have by challenging convergent evolutionary ideas here.
First time I’ve ever written to a blogger and so not sure how it goes.
Robert Byers
Toronto, Ontario

4 09 2007
Christopher Taylor

I would say this marsupial lion is exactly what it is . A big cat. The “minor” differences of reproduction and and a few anatomical bits pale to all the common anatomy with other placental cats.

Blink. Blink. Beg pardon?

Despite it’s being referred to as a ‘marsupial lion’, and a vague similarity to cats, Thylacoleo is still unmistakeably possum-like. Note the absence of any real canines, and the oversized incisors – exactly the other way around from true cats. Brian’s post doesn’t mention the at least semi-opposable thumb that Thylacoleo retained from its arboreal ancestors (you can see it here). And the “minor” differences of reproduction you mention are far greater than the differences that true cats have from humans. I therefore submit that you, sir, are also a cat.

Yes, there were also cat-like marsupials in South America. The “marsupial sabre-tooth” Thylacosmilus, however, derived from another group of marsupials, the now-extinct Borhyaenidae. It did not bear much resemblance to Thylacoleo.

4 09 2007

Hello Robert,

Thank you for the comment. I certainly was not expecting any creationist reactions to this post, and I will look at your website as soon as I have time. As you can imagine, however, I definitely disagree with your position. Chris already addressed this point in the comment before mine, but you wrote;

“I would say this marsupial lion is exactly what it is . A big cat. The “minor” differences of reproduction and and a few anatomical bits pale to all the common anatomy with other placental cats. likewise the marsupial dog, tapir, mole etc.”

The differences are certainly not “minor”, and what you propose seem to extend form the creationist fallacy that I’ve seen in many creationist books/tracts that there is no big difference between the extinct Tasmanian Tiger and the modern Grey Wolf. The differences, however, are not “minor,” the differences in various aspects of marsupials and placental mammals being great (i.e. the difference between the modes of reproduction certainly is a big difference). As I noted in the post above, living carnivores are most closely associated with extinct Miacids, their teeth forming the carnissal shear that links all carnivores together. Thylacoleo has it’s own carnissal shear, but it is very distinct from that of any other living carnivore. Likewise differences in the skull point to its marsupial affinities, and I can send you the wonderful anatomical papers in which Richard Owen outlines these differences if you like. Indeed, calling Thylacoleo a “big cat” does a huge disservice to what it is and is very sloppy science; even if you are to argue that it was made by God less than 6,000 years ago, it has far too many differences to be grouped in with the modern genus Panthera.

Likewise, you also mention Thylacosmilus but that is even more different in some ways from modern big cats than Thylacoleo. The massive canines of Thylacosmilus ran up into the skull almost over the eyes, and the details of its skull show that it is merely convergent with the later saber-toothed cats and nimravids (themselves going through parallel evolution). To group them all together just on basis of saber-teeth is irresponsible, as (by that logic) we’d have to group together gorgonopsids, musk deer, Hyenadon, and other distantly-related animals together just because they had elongated canines. The cliche may be all too appropriate for this conversation, but “the devil is in the details,” and it is at the details we must look if we’re to understand how closely (or how distantly) these animals are related.

4 09 2007
Zach Miller

I was going to ask you about those carnissal molars, Brian. In every marsupial I can think of, the carnissal tooth is a seashell-textured tooth that forms a slicing surface, rather than a grinding one. The carnissal molar is one of those enormous differences between marsupials and placentals that makes the two groups so distinct.

On a side note, to Robert: Masupials and placentals are as different from each other as, oh, dinosaurs and crocodiles. Sure, they’re both archosaurs, and they share a common ancestor, but it would be silly to call Allosaurus a close cousin of, say, Sarcosuchus. And yet crocodilians figured out on their own how to walk bipedally (at least for a little while) in the upstart popsaur Effigia, which is, for all intents and purposes, a small ostrich dinosaur.*

*It is NOT a small ostrich dinosaur, but it probably lived and looked much like one, although one might replace a feathery integument with a scaley, crocodilian one.

The point is that a particular lifestyle requires a particular anatomy. You wouldn’t say that ichthyosaurs are FISH, or even dolphins (or would you?) even though they’re basically the same shape, have the same sort of dental battery, and gave birth to live young. In fact, ichthyosaurs are closer to my pet geckos than to dolphins. Ichthyosaur ancestors began taking up residence in the ocean–an oceanic existance required a certain body plan, one which ichthyosaurs figured out quite quickly and to some success.

It’s the same thing with Thylacoleo. It’s basically a big opposum, but a megacarnivore lifestyle requires specific dentition and a body plan which allows the hunting of large prey animals. It just so happens that African dogs, lions, and Thylacoleo all converged on that body plan, a body plan that was required by the environmental niche they fell into.

This is not to say that an ancestral lion woke up one morning and said “You know, I think I’ll become a megacarnivore.” Not at all. Some selective pressures were present in each animal’s environment which allowed them to go into that niche at all–a lack of rival predatory presence, for example. To use dinosaurs as an example (because I’m the dinosaur guy), the only reason tyrannosaurs were successful at all was because in Asia, where they supposedly originated, there was not a large predatory presence. Instead, the largest carnivores were dromaeosauroids no larger than a big dog. The “need” was there for a carnivore who was able to go after the ornithopods and occassional sauropod in China and Mongolia.

Thus, tyrannosaurs quickly got larger and more successful, culminating (that’s such a terrible word) in Tyrannosaurus rex and Tarbosaurus baattar. Even tyrannosaurs had dinosaurian analogues. Abelisaurs in the south converged on tyrannosaurs in many ways, as did African and South American carcharodontosaurs.

4 09 2007

Zach; you probably know more about the tooth differences than I do. Admittedly, I’m a greenhorn in that respect. From what I understand the shearing cleavers of Thylacoleo are the premolars, the molars being greatly reduced. Wht I was trying for in the post was to relate them to the carnissal shear in true Carnivores, playing up the superficial convergence (or at least another evolutionary solution to the same problem). When I have taken in more I will go back and revise/clarify/update what I have said, so thank you for pointing that out to me.

5 09 2007
Robert Byers

Taylor, Switek,Zack.
I am saying that the evidences of ancestry are not teeth and pouches which I see as adaptations on a minor level but to the whole body shape from head to toe.
It is not just the cat like one but a great many like Squirrel, tapir, wolf. mice, mole, sloth. In fact this is a common theme in the fossil record. Same shaped creatures are everywhere been said to be unrelated and yet look the same except for a few details.
I know reproduction seems too big for many animals to acquire due to area but why not?
It is of less change then the great changes required by convergent evolution
to make such numbers of same shaped creatures.
Yes the sea has dolphines, and similiar dino fish yet I see these as very different from each other and the severe need to adapt to a water world is a special case.
Teeth and bones are just calcium collections and should not overrule all the many numerour other anatomical configuration.
NOVA had a show on the marsupial lion and it sure doesn’t look like a big possum but like a common cat.
I have seen video of the marsupial wolf and it is very dog like.
Anyway my idea is more then about marsupials but a bigger challenge to convergent evolution as being unlikely and missing the simple answer first.
Robert Byers

5 09 2007
Christopher Taylor

But why would animals change reproductive mode because of area? Especially considering that not all the endemic mammals of Australia are marsupials – Australia has a quite considerable radiation(s) of rodents. [Brackets around the s because I have no idea whether or not the Australian murids are supposed to represent a monophyletic group, or how many times murids are supposed to have entered Australia] Not to mention bats. And there’s even a couple of monotremes kicking about, though admittedly echidnas do have a pouch.

Convergence does not “miss the simple answer”. In this case, convergence is the simple answer. Why are there so many marsupials in Australia and (to a lesser extent) South America, but no marsupials in Eurasia? Why marsupial lions in Australia, but placental lions in Eurasia, Africa and North America? Why marsupial wolves in Australia, but placental wolves in Eurasia and North America? Why marsupial phalangeroids in Australia, and placental squirrels everywhere else? If you regard all these as unrelated, it makes less sense than Vincent Price driving a bus ever did.

5 09 2007

Welcome back, Robert. You wrote “I am saying that the evidences of ancestry are not teeth and pouches which I see as adaptations on a minor level but to the whole body shape from head to toe.”

We’re not just talking about superficial characteristics either, Robert. In order for Thylacoleo carnifex to somehow be an big cat that has been radically adapted, you’d need to explain (at least) the following;

1) Why it’s incisors differ so greatly from those of “true” big cats of today. The incisors of Thylacoleo are (as you can see from the pictures above) quite-rodent like and vary in length/size within the genus (remember that T. carnifex was only the last of the lineage).

2) Why the cleaver-like premolars of Thylacoleo have been adapted in their present form. If it evolved from big cats, then it would already have had a set of teeth that would be well-adapted to cutting flesh called the “carnissal shear” (read above), made up of premolars and molars in the living Carnivora.

3) Why brain size was reduced to allow for larger muscle attachments. If you look at the picture of the bottom of the skull, you can see how the openings on the side of the skull allow for massive jaw muscles but the space between, where the brain case would lie, is quite small.

4) Why Thylacoleo only retained retractable thumb-claws instead of the full set as seen in most big cats (Cheetahs being the exception of entirely losing the ability to retract their claws as they use them as cleats).

5) Why Thylacoleo, if derived from placental mammals, became a marsupial. Why would a mammal that would give birth to more well-developed young go “backwards” and develop a pouch as well as give birth to underdeveloped young that it would have to keep safe for a time (probably inhibiting the amount it could hunt, and if it did it could risk the life of the baby). Are all marsupials, then, “devolved” placentals? When/where/why did this occur?

Indeed, Robert, merely saying “It looks like a big cat” is not enough to prove a relationship. That is the starting point for your hypothesis, but you’ve offered no evidence (outside personal credulity) to support your view that Thylacoleo really could be Panthera carnifex. In fact, even if such a relationship were real (and again, there’s no evidence to show that it is), you’d have to evolveThylacoleo quite a bit in order to get something like a lion to lose most of its retractable claws, give it rodent-like incisors, make it a marsupial, and sacrifice brain size for muscle attachment. In terms of science, merely saying “This one looks like another one, therefore they must be related” is sloppy reasoning, and we know from other lineages (like Nimravids and Phytosaurs) that convergence and parallelism in evolution does occur, especially if animals are occupying the same ecological niche in different points in time.

5 09 2007
Zach Miller

I think the problem is that we’re calling Thylacoleo a “marsupial lion,” which, of course, gives it the “lion” name. We should be calling it a carnivorous possum or something. While I understand and appreciate that calling it a “marsupial lion” actually makes it COOLER because of the convergence aspect, that will no doubt lead some people to broad generalizations.


27 10 2007
Red-haired Neandertals « Further thoughts

[...] Australian and South American marsupials resembled their eutherian counterparts – dog-like and and cat-like marsupials evolved which bore striking resemblance to “real” members of the dog and cat [...]

12 11 2007

Hi all,
Robert seems to have done exactly what creationists are good at,
turning a scientific debate into a quazi religeous mish-mash!
These creatures predate the aboriginal history of Australia therefore predate the dreamtime,where does creationism fit into the picture?
By believing the Aboriginal race and all others to be less than 6000 years old you are demeaning their history and the age long development of a race and culture you obviously don’t know anything about.Then to go on and speculate that the evolution of Thylacoleo is also less than 6000 yrs shows a distinct lack of evolutionary understanding.If creatures evolved as fast as you and your colleages speculate we would watch the differences in evolution happen every millisecond.Animals and plants would metamorphasize before our eyes and within their own life spans!
Have a look at the bandicoot assemblage found at riversleigh and it wont be too hard too see where the unique Thylacoleo has its ancestry,

16 03 2008

I Loved this article very much. I still have one question however some how. Which parts of Australia did the Thylacoleo live in? I’m also trying to do some report like this and would appreciate it if you could answer my question.

18 03 2008
Watkin Davies

I would like to make it known that both thylacoleo carnifex (?)
and thylacine are both extant in Australia and doing quite well thank you.
Re TC I refer to website forum of
There is a report of a recent sighting of a Thylacoleo, and specimen of hair I received from a dingo trapper in NE Victoria proved to be thylacine.
It has long been known to bushmen and investigators that these animals are still in existance, although official circles still deny their continued existance.
Kind regards to all Wally

26 03 2008
Timmy Davis

I find thylacaleo very interesting and would like to see a 3-d version of how it hunted and to know if it bite the spinal cord or if it sufficated it’s pray by its esophiguse.

29 04 2008
Thylacoleo, a Unique Extinct “Super-Predator” « Nimravid’s Weblog

[...] Switek covered Thylacoleo last year on the previous incarnation of his blog, Laelaps (now at its location at ScienceBlogs). Darren [...]

1 07 2008
Graham King

I would say this marsupial lion is exactly what it is . A big cat. The “minor” differences of reproduction and and a few anatomical bits pale to all the common anatomy with other placental cats.

Teeth and bones are just calcium collections and should not overrule all the many numerour other anatomical configuration.

Hmmm, Robert… I take exception to the phrasing that anything in biology is ‘just’ anything ‘minor’ or ‘a few bits’. I can understand the desire to radically simplify and generalise for the sake of some more easily-manageable overview but, for me, ‘God is in the details’.

I see the beauty of the created natural world (and divine wisdom) embodied in both these facts –
(1) that nature is comprehensible in its broad detail by a little child (most toddlers readily can categorise as either domestic ‘dog’ or ‘cat’ even varieties of these genera which are new to them); and (once shown some examples) can recognise any of a huge range of structures as ‘a tooth’.
(2) that nature holds enough complexity and variety to fascinate, delight and dumbfound even the most intelligent and well-educated (there is so much more to say even about these than just ‘dog’ or ‘cat’ or ‘it’s a tooth’).

There are both overall hierarchies of meaningful order, and abundances of particular detail.

These two qualities make appreciation of nature both universally accessible (to all ages, cultures, and intellects) and inexhaustibly interesting.

To attempt to assert the primacy of (1) over (2) for understanding biology is (I would say) to oversimplify, missing or glossing over much detail and difference that is worthy of our most careful attention. It is, in effect, failing to appreciate the handiwork of God. God surely is not simple-minded, but also subtle and shrewd, wouldn’t you agree?

While I would agree with you somewhat – that it is possible to ‘miss the wood for the trees’ at times, by getting obsessed with detail while lacking wider perspective –

I think overall that reverence lies in being more, not less, appreciative: of BOTH the particular distinctive qualities (as well as the common qualities) of all that exists.

6 07 2008
Guess this image! - Page 31 -

[...] Posted by RedFox Marsupial lion Better look at the skull here from this page. The teeth on the front are the large incisors and the back ones are premolars with no big canines [...]

13 07 2008
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19 08 2008

Hi Laelaps,

I’ve a quick question which I hope you may help me with – you recently mentioned in your reply to Robert on number four, that the marsupial lion only had retractile thumb-claws, rather than a full-set of retractile claws, I’ve always assumed this, although I was wondering if you had a source or reference which directly states it?


19 08 2008

Hey. Just found your post while researching the extinct “lions” etc of Australia. Good stuff here. Check out the post i just did tying the koala to Matthew McConaughey. Seriously. See you at the Kangaroo Rodeo…

2 11 2008
hairy muscle bears

hairy muscle bears…

I’m usually not big on strawberry flavors, but I got a single packet…

22 02 2009
Samir Kagadkar

Greetings from India
Excellent post, made a very interesting read.

31 07 2009
Peter M

Great blog, and excellent info! A shame the creationists always think they have something to add to any discussion of prehistory. I wonder why it is that their online comments are always so riddled with basic spelling mistakes, on a far greater scale than the average teenage gaming forum. And this is all quite apart from their crudely conceived and disconnected “ideas” and “scientific” insights on such arcane topics as “dinosaur fish”…

2 08 2009
Feroz Y Khan

I wanted to say that I know and am part of the marsupial and mammal cat god’s family.Sumner for house cat.Ravage in Transformers Revenge of the Fallen was excellent.Marsupial cats need to raised by mammal cats and bobcats to regain predation,calls like cougar call.Thylacine is capable of this,losing its heritage and a major war British and whiteman.Thylacines are cats and tiger their food to gain weight and size.Lost their appetite and lost weight and FLIR.Once the Pacific Islands marsupial cats have watched wild kingdom show about cougars or North America they will re-learn and learn new things.Marsupials are chippy in their strengths.Kokanee Ranger.V for Vendetta mask.Cat family is a balance and when one end goes down we have a system to send to maintain a balance,cats vs man and we have a great record.Marsupial cats warfared against dinosaurs and dragons,eating their young and out fighting them.Enemy ate predators as food as Great White.Cats have their own language important.And of course petting.Cats are powerful and use APB like adaptations and modes,night vision then make decision to go in on Elk or moose which is bigger than a truck.Bobcat being 40lbs.Then it starts many stages and processes towards the kill.Camaflauge in the woods and seasons.Dogs of all sorts are cats enemies as bears.Cat are cats.

6 06 2010

Can I have some of what Feroz Khan had for breakfast?

Lovely article, Brian..I loved the artwork too.

6 06 2010

Also, I think we may be getting close to godwins law on this thread.

23 10 2010
pet geckos

The Marsupial Lion is the largest meat-eating mammal known to have ever existed in Australia, and one of the largest marsupial carnivores from anywhere in the world. Thanks.

31 10 2010

The Marsupial Lion is the largest meat-eating mammal known to have ever existed in Australia, and

23 12 2010
застраховка живот

Wonderful article thank you.

16 01 2011
the novel network

I absolutely love reading your blog. Pleade Keep adding information. Thanks.

9 05 2011

Hi, you have a nice blog. I also have a page about animals which, although in Germany but the top left is a menu English but also you can read everything in english. Greetings from Germany :-)

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