Thursday, May 26, 2016

Your Puny Lipped Sabertooth Kitty is SMASHED!!

I knew in my last post that some might take exception to my tone a bit... ahem... maybe the 'rastling analogy went over their heads. I went with my gut and my gut said take the fight to 'em which is what I did knowing full well that the blowback would be real and palpable. However the blows I delivered came in the form of valid, scientific arguments.  The majority of blows I received were anything but.  Again some might take exception to my approach calling it "antagonistic " or "childlike" but these critics did not get attacked like I did. No one enjoys getting called "inane", "ludicrous", or a "jealous idiot" (Ok I might be jealous some times and an idiot at other times but never the two at once). But this is all the majority of the arguments really amount to; name calling; dismissive; and clinging to custom. While there were some intelligent questions and criticisms I did not find any of them damning to such a degree that they warrant scrapping the hypothesis. Indeed the multiple lines of evidence I offered in that post will be further augmented in this post to such a degree that any attempt to invalidate this hypothesis need to disassemble each individual argument one by one not merely poke holes in individual arguments to cast shade. Because as much as I pleaded and prodded for scientific reasons why a small lipped sabertooth predator is the better and more supported option than what I suggested I received nada. Nothing. Nunca. There is literally nothing that puny lipped sabertooths give advantage to over big lipped ones. Indeed big lipped sabertoothed predators should have always been the null hypothesis but cultural inertia, dogma, and "awesombro" exposed toothiness got in the way.

Smilodon populator. used w/permission credit deviantartist Dontknowwhattodraw94 (Robin Liesens)

Another possibility, more classically felid. credit deviantartist Unloborgis. used w/permission (c) Sergio Perez

All the while I knew that if I shook the tree hard enough something might just fall out... which it did and it splattered everywhere.

Time to crack this thing wide open...

And crack is the word of choice here because as traditionally depicted cracking is what sabertooth canines would be doing a lot of. Not just because of being exposed to blows from prey/competitors. Not just because of grit working away at the denticles. But because of chemistry.

Special kudos to Brad McFeeters for turning me onto the abstract of an as yet to be published work on the relationship between enamel health, saliva, and closed oral lips. Something any good dentist could tell you. Indeed it was a man who said he teaches students taking the dental admission test that presaged this very fact to me in a comment from my last post:

Please excuse the "appeal to authority" but it is none other than the American Dental Association that refers to saliva as "the bloodstream of the mouth" :

Intuitively this makes complete sense. Ever fall asleep with a stuffy nose and then wake up with a mouth that feels like a crypt? The bad breath and general oral malaise of just spending one night with your mouth exposed and dried out is but a preview of the dental horrors that would befall a sabertooth predator spending a lifetime with its physiologically expensive canines unsheathed.

Here is an excellent, easy to follow, and well referenced summary of the benefits of saliva by the European Food Information Council:  Saliva - more than just water in your mouth

Of special relevance is the chemistry of saliva which is crucial in maintaining the mineral balance of tooth enamel and dentine and preventing the loss of calcium and phosphorous. I am not going to pretend to be a chemist or that I can explain it any better than they do so let me just outsource their summary below:

Essentially not having saliva - which is buffered with loads of calcium and phosphorous - would open up the crystal structure of hydroxyapatite (the building block of dentine and enamel) to chemical attack.   The attacking molecule that would strip calcium and phosphorous out of the crystal structure is... water "in water the crystal would steadily lose ions form the surface and shrink". Best keep your cutlery sheathed and lubricated with saliva otherwise you are looking at some brittle canines because water is pretty much everywhere!!

Time To Stomp the "Tusk" Argument to Smithereens

Clearly I did not state my case strongly enough in the previous post that the last thing you want to compare sabertooth canines to is tusks which differ in just about every fundamental metric from sabertooth canines. Never the less you still have people chiming in "but what about fanged deer"? Please don't insult these proud and magnificent predators by comparing them to..... deer ( I jest, just a little). To be fair musk deer have continual growth of their canines and as I will explain shortly tusked deer will most likely share histological features of other tusked animals. Let me reiterate; tusks are sexo-social symbols and hence need to be displayed while sabertooth canines are not; tusks are used for not only combat but coarse gouging of sediment, bark, roots, and other gritty abrasives - sabertooth canines do none of these activities, in fact to the contrary, the fine serrations on many sabertooth canines would be damaged through excess grit; tusks grow constantly, sabertooth canines do not. These are all patently good arguments that are also essentially adaptationist in their approach. However paleontology and evolutionary theory have fallen out of love with adaptationism to some degree dismissing such arguments as "just so stories". I blame Stephen Jay Gould for this pervasive sentiment. I don't mean to kick a man when is down (literally six feet under in this case) but Gould was a little less than precise in giving us good examples of evolutionary spandrels after all. But I digress.

This just means I got to look a little bit harder and deeper than "just so stories" to persuade people that tusks are the last thing that you want to compare to sabertooth canines. Luckily enough for us there is quite a bit of information out there on tusks because ivory - the cultural trade and carvings of large animal teeth - has been a pretty important thing in human economics that people have looked at. When we investigate the histology of  tusks (i.e. large exposed teeth) there are some interesting surprises...

credit USFW services

Notice that in the schematic above there is just a bit of enamel at the tip but the bulk of the external layer is actually cementum, followed by dentine. Now in the hierarchy of hardness scale enamel is hardest, then dentine, and finally cementum. However given that enamel occurs only at the tip where it is actually worn away during the life of the tooth it is a bit of a paradox. Why would tusks - which are subject to all sorts of rough and tumble activity - only have such a paltry layer of the hardest structure which is enamel? Not only that - it is counterintuitively cementum that covers the bulk of the exterior of tusks which is the softest of the three materials? It's a bit of a paradox that tusks disinvest in enamel but invest heavily in the softer tissues of dentine and cementum (also btw which is why ivory can be carved). The reasons I would suggest are manifold:

1) Enamel once it is formed can not keep growing, only maintained. Dentine on the other hand can be grown continuously via odontoblastic cells in the pulp cavity - which is why tusks keep growing. Cementum too can repair itself and grow continuously via cementoblasts.

2) Enamel is the hardest structure of the three but also the most expensive physiologically to grow, form, and maintain. Minerals are very precious things after all and investing so much mineral wealth in a structure that will be winnowed away is maladaptive.

3) Because the enamel in tusks is not constantly bathed in a buffering solution of saliva that maintains calcium and phosphorous balance of the crystal structure it is prone to not only physical attack but chemical. The investment of enamel in the tip of the tusk is a throw away investment. Over time it will be lost. From USFW on elephants/mammoth tusks: "Enamel is only present in the tusk tip in young animals. It is soon worn off and not replaced."

4) I will suggest that cementum and to a lesser extent dentine - having less of a solid crystalline structure than enamel and a higher percentage of other protein tissue that form it (e.g. collagen) - are less subject to chemical attack than enamel in the exposed state and offer an ideal compromise: just enough hardness to get the job done without the excess chemical attack that enamel suffers. Again, both dentine and cementum can grow constantly while enamel can not.

If this is a robust and true pattern we should see it again and again in animals that leave their teeth (i.e. tusks) exposed to the air. Through convergence this prediction should be met and these animals will disinvest in enamel on the exterior layer of the tooth and have relatively higher investment of the less mineralized and softer dentine and cementum.

And gee willikers look what we have here:

Walrus (Odobenus rosmarus)

From the USFWS: "The tip of a walrus tusk has an enamel coating which is worn away during the animal's youth."

cross section walrus tusk. C=cementum, PR=primary dentine, SD=secondary dentine

Also of note cementum is softer than dentine. This follows the somewhat counterintuitive pattern in having the least mineralized (softest) part of the tooth exposed to the environment as to not become demineralized. The cementum literally shielding the dentine from exposure.

Sperm and Killer Whales (Physeter catodon & Orcinus orca)

From the USFWS: "Both species display conically shaped teeth with a small amount of enamel at the tip. The rest of the tooth is covered by cementum."

killer whale
Which of course reminds me of the population of offshore killer whales that specialize in feeding on deep water sharks. This population pay a heavy toll in the form of declining dental health with old adults in such populations showing severe tooth wear reduced to gumming shark liver and the young doing most of the tearing up. Not too surprising that captive killer whales have horrible dental issues as well.

Narwhal (Monodon monoceros)

From USFWS: The narwhal horn (actually a modified upper incisor): "Enamel may be present at the tip of the tusk."

Wart hog (Phacochoerus aethiopicus)

From the USFWS: "a longitudinal enamel band with approximately one-half to two-thirds coverage mark the tusk's surface in the raw unpolished state."

Wart hog
Hippopotamus (Hippopotamus amphibius)

From the USFWS: "A broad longitudinal band of enamel covers approximately two-thirds of the surface area of the tooth... The surface which is not coated with enamel displays a very thin layer of cementum... Hippo incisor crowns are covered with enamel."

Wait a second here, the hippo seems to be breaking the pattern of tusked animals that have minimal enamel coating on the exterior of the tooth. What is going on here? All is not as it seems with this tusked animal. The hippo is a tusked animal that keeps its tusks and dentition covered with big lips that don't quit. Therefore it gains the protective benefits of saliva and can afford to have enamel rich dentition. By the way why does no one consider the massive lips of hippos preposterous or ridiculous but big lips on a smilodon? that is just ridiculous.

credti Quartl CC3.0 Huge Lips to Cover Huge Tips
The Croc Question

"Ok then, what about crocs? They leave their teeth exposed to the elements - including water - which can itself strip away calcium and phosphorous?"

All is not as it seems as well with our smiling crocodilian friends. Their sinister smile betrays a sneaky way around the problem of exposed teeth. First of all - analogous to ever growing tusks of mammals  - crocodilian teeth have the ability to get replaced. Second of all crocodilian teeth show a histology more congruent with tusked mammals than the enamel rich dentition of mammalian carnivorans or predatory theropods. Their teeth actually act more like miniature tusks in that they too share the pattern of a thrifty use of enamel on the exterior.

A recent study of this very issue (Enax, 2013) provides some telling information:

Some things attract my attention here.

"Virtual sections through the tooth and scanning electron micrographs showed that the enamel layer is comparably thin."

To beat that drum again that is exactly the pattern in tusked animals with exposed teeth and opposite the pattern in animals with closed lips and sealed mouths that allow teeth to bathe in saliva and remain enamel enriched.

"The crystallites in the enamel are oriented perpendicularly to the tooth surface."

Very interesting here in that the crystal structure - being perpendicular to the tooth surface - is oriented in a manner that minimizes exposure to the outside environment. Could a very logical (and adaptationist) hypothesis be that this orientation is not haphazard but in fact that it has selective benefit in minimizing surface area exposure to chemical attack from the environment?

From the discussion section and conclusion:

The authors explain the thin layer of enamel in crocodiles which contrasts to the thick layer of enamel in mammals due to "the enamel of crocodile teeth is very thin.. because crocodiles do not use their teeth for cutting and chewing." I don't really understand why people say crocodile teeth do not cut, I mean tell that to anyone or anything that actually who has got bit by a croc. Those teeth do cut. Point taken they are >mainly< graspers but they can inflict some pretty nasty damage as well.

Never the less it is readily apparent that the authors failed to compare croc teeth to exposed mammalian teeth (i.e. tusks) which they do share a convergence of composition, microstructure, and hardness. By the way also interesting that croc teeth compare in hardness with human teeth given the high disparity in bite strength. Probably helps in preventing brittle deformation in croc teeth but still strange to think about.

I would venture to say that in the worn teeth of old crocs all of the enamel has been worn off through either mechanical or chemical wear and you are in fact looking at the dentine after the thin enamel tip has been worn away.

any enamel left in those tooth crowns? I doubt it. American crocodile. credit Daderot public domain

 Shark teeth... well I don't even want to confuse the situation further.

The main point is that croc teeth and mammalian exposed teeth (i.e. tusks) show congruence in composition and structure that suggests a possible selective advantage in being thrifty with the amount of enamel coating the tooth. Tusk bearing animals that maintain an oral seal via lips such as hippo can coat their teeth with relatively more enamel due to the salivary benefits to enamel health.

So the million dollar question is: if sabertooth predators indeed left their canines exposed to the environment then they should show histological tooth characteristics similar to crocodilians and exposed tooth bearing (i.e. tusked) mammals such as minimal enamel coating of the tip and potentially a layer of cementum covering the coat of most of the tooth. If they were just good ol' mammals that kept their lips shut and their teeth sheathed and bathed in saliva then we should see bountiful amounts of enamel especially on the exterior of the tooth.

So which is it?

Unfortunately I can not find adequate and thorough histological work on the microstructure of all sabertooth predators. But I can find such work on the creme de la creme, el utlimo hombre of sabertooth predators Smilodon fatalis. If this predator keeps the pattern of thick enamel forming the exterior of the working tooth and not just the tip it squarely lines up with animals that cover their enamel rich teeth in big luscious lips and bathes them in a protective broth of saliva. And if this penultimate of sabertooth predators can cover its extreme canines with lips there is all the reason in the world to expect all the other sabertooth predators to fall in line.

Answer: Smilodon fatalis is a good ol' mammal that maintains lots of enamel... ergo it had big ol' lips draping over said enamel.

*Update thylacosmilids had more of a tusk like growth pattern with only a shallow enamel layer

From the paper Cementum on Smilodon sabers (Riviere & Wheeler, 2005) these depictions clearly label the cementoenamel juction. Everything on the exterior of the tooth towards the tip from this junction is enamel. Smilodon is not like a tusked mammal or crocodile but congruent with every other enamel rich mammal that sheathes its teeth in lips and saliva.

Interestingly the Riviere & Wheeler paper came to the conclusion that gingiva - in other words gum tissue - covered the root of the tooth all the way to the cementoenamel junction.

From (Riviere & Wheeler, 2005):

This interior soft tissue protection would inhibit infection, alveolar bone resorption, periodontal disease, additional tactile capability, and tooth stability. In short very consistent with the soft tissue benefits of large lips and a sealed oral cavity for tactile ability, protection, lubrication, and enamel health. It all meshes together to create a very gummy, lippy, and infinitely more adaptive vision of these predators than is classically portrayed.

used w/permission credit LWALTERS. deviantart page LWPaleoArt

Here is a more classically felid look that could work too.

This is for the haters - if your mind changes as the facts change this need not apply to you, move along and let it not apply to you - but if you attacked me with name calling or just dismissed my arguments as "ludicrous" then yeah, this is aimed directly at you. Can you feel that?

Call me childish, but hey, talk to me after you take a chance on something and take the shots I do. Gonna rub it in their face just a little bit.

And finally back to the yet-as-unpublished work by Robert R. Reisz that Brad McFeeters brought to my attention after the last post was published. Presented at the 2016 Canadian Society of Vertebrate Paleontology. Unpublished stuff is always "iffy" but hey if CNN is gonna cover it and the press is all over it then fair game for me I say. So far the press has put out the stock line you see in all theropod related news and somehow T. rex has to be the star of the show... all the while (predictably) ignoring the more obvious implications for sabertooth predators that this study also hints at.

I am very bolstered by the observations by Reisz and Larson on the histology of tusked mammals differing from theropods which converge with my argument regarding tusked mammals falling down as an analog to sabertoothed predators. However I would certainly encourage Reisz and Larson to look more closely at their statement "we propose that this requirement of hydration is not possible to maintain if the tooth is exposed permanently". As I discussed earlier saliva's benefit has much to do with maintaining chemical equilibrium of enamel while water that is not buffered with calcium and phosphorous can strip it away. Water has some pretty unique chemical properties (dipole moment, net negative charge) that can overtime strip enamel of positively charged calcium and phosphorous. Not saying that hydration does not play a role in all of this - it likely does - but chemical equilibria is another important aspect of enamel health. Again, remember hippos were the only "tusked" animals that have a lots of enamel on the exterior of the tusk but only because they keep them bathed in saliva.

To drive the point home one last time:

Facial tissue completely or mostly sheathing the upper canines as is corroborated by ALL extant terrestrial mammalian carnivorans and is the best null hypothesis; exposed and constantly growing tusked mammals use their non-serrated tusks for coarse hacking, chopping, digging, combat and display and are an inferior analog to sabertooth canines and need not be considered as they fail in comparison along nearly every metric; exposed toothed mammals (e.g. tusked) and exposed toothed crocodilians have differing tooth histology from sabertoothed predators*; unlike smilodon these animals have minimal enamel laid down at the tip of the tooth often worn away during the animal's lifetime; exposed toothed animals have an exterior tooth largely covered in cementum or dentine, both of which can grow constantly unlike enamel; saliva plays a crucial role in the dynamic chemical health of enamel; saliva provides a buffering role in hydroxyapatite crystal as saliva is enriched with calcium and phosphorous preventing demineralization of enamel; this salivary coating is only maintained in closed mouth (e.g. lipped) animals; the clouded leopard which has long canines comparable to many sabertoothed predators covers its canines completely; all five radiations of sabertooth predators display osteological evidence of protective sheathing on the lingual inferior aspect of the canine via a mandibular flange - a logical evolutionary inference is that protection for the superior labial aspect of the canine was also selected for in the presence of a large fleshy upper lip; the presence of this large fleshy upper lip is corroborated osteologically by the relatively large infraorbital foramen found in all sabertooth predators; this large infraorbital foramen supplies the blood and nerve supply to an extremely large and sensitive "nerve pad"; the extremely innervated nerve pad provides tactile support to make precise and crucial placement of canine entry for bite as well as early warning for violent torsional twisting of prey that could damage/snap canines; such tactile support would be diminished or non-existent in sabertooths depicted with modest sized upper lip region as this area would be scrunched away from the bite area when the mouth is opened and it would be the vulnerable canines that would "feel out" where to bite; extensive gingiva possibly reaching up to the cementoenamel juction protected, sheathed, and provided tactile support to the canines; large lips, gingiva, and supporting nerve pad evolved in lock step with increasingly large canines and forequarter strength for maximum safety and efficiency in these highly precise yet vulnerable predators.

Your puny lipped sabertooth kitty is not only smashed...  it is curb stomped!!

Destroy all those lines of evidence systematically and I will disavow this hypothesis. Come at me bro.

No we don't need a sabertooth mummy, we already have more than enough to sensibly conclude LARGE LIPS FOR THE WIN!!

*Update thylacosmilids had more of a tusk like growth pattern with only a shallow enamel layer

Special thanks to the work of Jaime Headden and of course this post has the spirit of "All Yesterdays" (Naish, Witton, Kosemen) smeared all over it. Whether or not these researchers agree with my conclusions this work would not have been compiled without their existing works, thoughts, and efforts.

Also special thanks to the deviantartists who took a chance on depicting big lipped sabertoothed cats. I fully believe that your risk taking will end up on the right side of history.

P.S. This was just the warm up. I'm coming for ya' next lizard lipped theropods...


Ivory Identification Guide. USFWS. Natural Ivory.

Saliva - More Than Just Water in Your Mouth. EUFIC.

Enax, J., Fabrittus, H.O., Rack, A., Prymak, O., Raabe, D., Epple, M., 2013. Characterization of crocodile teeth: correlation of composition, microstructure, and hardness. Journal of Structural Biology 184 (2013) 155-163 link

Reisz, RR, Larson D. (2016) Dental anatomy and skull length to tooth size rations support the hypothesis that theropod dinosaurs had lips. unpublished abstract 2016 Canadian Society of Vertebrate Paleontology

Riviere, HL, Wheeler, HT. 2005. Cementum on Smilodon sabers. The Anatomical Record. 7 June
2005. 285A 634 - 642. link

Wallace63. CC3.0

"A Long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom". Thomas Paine

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khalil beiting said...

Haha great post Duane! Without a doubt, a lipless Smilodon is near impossible. And yes, I have seen many childish antics online about your new theory. I haven't seen any good arguements against it, although the only true arguement regarding it is how it's lips would be less bulldog and more feline in appearance. This amazing picture right here is my personal favourite reconstruction as of yet:
I suggest you add it to the post since it's such a marvelous reconstruction. Thanks again for the great post!

Anonymous said...

You forgot something, all felines tend to use their tongues to lick themselves over and over again, and not just for cleaning. What would have stopped the saber-tooths to lick their sabers to maintain them wet when needed, and to clean them?

D-man said...

If this doesn't convince anyone that sabertooth cats had covered canines, I don't know what will.

Amazing post by the way. You just cemented the idea that saber tooth cats had covered canines even further. I heard some people say that this is unlikely because, "they probably used them for display as well" talk about dumb. Why would an animal with massive SERRATED canines use them for display. If an animal were to use those canine for display, they would have no serrations on them.

"This was just the warm up. I'm coming for ya' next lizard lipped theropods"
Can't wait for that post.

Duane Nash said...

Thanks khalil and D-man. Khalil I like that pic too and asked if I could use it on this post. People will still need convincing but at least these posts weaponize proponents with good talking points. I don't have the time and energy to battle every online battle over this idea so hopefully others take up the arguments. The real challenge after getting more consensus in the paleo community (don't hold your breath there these things tend to move slooooowly) will be convincing the lay public (wake me up when that is done).

@Anonmyous. (please but down a name in the future) Yeah I would put the notion of smilodon constantly licking its canines under "special pleading" and also a constant waste of moisture. Are you suggesting that it would lick its canines while it slept too? Much more simple and parsimonious to have the big lips their for saliva lubrication as well all the other reasons I listed and which I am not going to repeat here.

D-man said...

Another thing you should consider: If Smilodon had those massive pearly whites out in the open, those teeth would basically be big white beacons in an environment with brown to green grass. Anything looking towards the cat will see those massive pearly whites and run away before the cat gets a chance.

D-man said...

Duane, what would that protrusion connected to the flange be like. I heard you say it would be flexible and have lots of stem cells to help it build back the healing but wouldn't make more sense if that protrusion was made out of thicker skin akin to the thickness of elephant and rhino hide making it less flexible, therefore not allowing the protrusion to move with the tooth when the cat is about to bite something?

Duane Nash said...

@ D-man there are several options. I am not overly dogmatic about which one people prefer as long as those knives are sheathed!!

Tuomas Jokela said...

Now, the reconstruction khalil posted would actually work. The animal must have been able to retract the lips well out of the way. An isolated thin, flappy, hanging piece of skin would also be way more vulnerable to unintentional biting (everyone who has given munchy-crunchies to flappy-lipped dogs knows what I mean).

However, a clouded leopard like solution - sabers inside a sheath formed by the lower lip - is the simpler solution for all sabertooths with a mandibular flange. This leaves Smilodon the odd cat out with its reduced flange.

Duane Nash said...

@Tuomas Jokela Yeah I am starting to think the same. I honestly don't know enough about the muscles that lift the lip region out of the way to say one way or the other what is best or that one interpretation is more favorable but the image you speak of - which I updated the post with btw seems to be gaining favor so maybe there is something to it!! In either case I think it is a great example of how new/revived thought on an old beast combined with a quasi-sourced input from numerous artists and visionaries can work together to provide new insight.

I have heard that before about clouded leopards fitting their canines into sort of "pockets". I am not negative on the potential that they do this I just can't find any unequivocal images of it? Can you or anyone help in this manner?

On sabers inside a sheath for mandibular flanged sabertooth predators. As of late I have been converging on the same conclusion. This could explain the Isturitz statuette (although that will always be controversial to a degree). Smilodon may indeed be the odd cat out, a freak among freaks.

Lucas Attwell said...

The pockets?

Carliro said...

Ironically thylacosmilids have more obvious evidence of sheathing.

Though, an animal incredibly important in this argument (that may even topple it) is Monodelphis dimidiata, which is closely compared to sabertoothed predators:

The problem is that it's unclear if it sheaths its saberteeth or not. Virtually no unambiguous pics of males exist.

Andrew Raymond Stück said...

Well, to be fair, most people DO think hippos look pretty ridiculous...

I get your point though, and against every instinct in me, I think I might agree with you on this issue.

If you can deal with the choppiness of Google Translate, you might be interested in Andrea Cau's blog post on the subject of paleo-lips. Tusked deer are mentioned.|en&tbb=1&ie=UTF-8

Tuomas Jokela said...

Duane, I thought the same about the Isturitz 'Homotherium'. It would be a perfect example of a 'chinny' sabercat with its canines sheathed. But like you said, we never might really know.

As for the clouded leopard, a quick Google image search for yawning or grimacing clouded leopards brings photos which IMO clearly show a sort of pocket in the lower jaw for the upper canine. It appears to be formed by an inner lip and an outer lip (!) and although I wasn't entirely convinced by simple image searches, this 'double lip' configuration seems to be a standard in cats. The things you look for...

Anyway, here are some examples. Look for the space right behind the lower canine, of course.,d.bGs&psig=AFQjCNFBuKhlQrPKnFh9vfi--nBts7LNcg&ust=1464463746526027&cad=rjt
Here's a clouded leopard going full sabertooth with its gape - apparently it's the only modern cat able to do the 90° gape:
Herp derp! Even a modern 'sabertooth' can get its sabers chipped.

Tuomas Jokela said...

Here's one more, where a sheathed upper canine can apparently be seen jutting from the skin of the lower jaw.

Also note the mandibular vibrissae, which brings me to another point: sabertoothed mammalian predators usually had multiple large mental foramina in the mandibular flange. You can see where this is leading to.

D-man said...

@Tumos Jokela is the thing you are leading to is that Smilodon does not have this. Like Duane said, the flange possibly supported a peice of thick skin for the saber to slide against.

Duane Nash said...

No D-man what Tumos is getting at and which I am leaning more and more towards is that Smilodon was the exception to the pocket adaptation. In essence the sabertooth predator with relatively small canines (Homotherium for example) could easily have put their canines in a pocket structure (like clouded leopards) which I think is actually just a hollow between the gums and outer lower lip. The more extremely flanged sabertoothed animals took this adaptation to the hilt.

I have been thinking a lot about marsupial sabertooths i.e. thylacosmilids which seem to show more of a tusk style of tooth growth. Marsupials are known for having relatively low lifespans too... opossums (which everyone loves to show me pics of their exposed canines wowee wowee) live like one or two years if I recall. So no great need to preserve a canine for an opossum which let's be real uses that canine more for threat anyways it is not taking down large prey or prey even as big as itself.

But back to thylacosmilids I would be very curious how long they live. Did they just live a couple of years in which they just went to town with those evergrowing canines?

babehunter1324 said...

I think that focusing mostly on Smilodon might be somewhat prblematic, Smilodon is an outlier when it comes to the lenght of the canines and the characteristics of the lower jaw.

I could totally see some gnera like Homotherium and even Megantereon with a very cloud leopard like solution, with most of the canines fitting on pockets of the lower jaws and upper canines only marginally longer than in modern felines. Taht would be problematic on Smilodon, though...

Carliro said...

Again, can we address the Monodelphis dimidiata in the room?

But at any rate, thylacosmilids do seem paradoxical. They're the sabertoothed predators with the most evidence of sheathing, but they also possess essentially rodent-like constant fang growth and tusk-like morphology.

I think they were sheathed and simply extra-reinforced.

Carliro said...

Also, thylacosmilids are not marsupials

D-man said...

I am suprised no one brought up madrills or other monkeys.

CoreyStudios2000 said...

Who are to question evolution? Who are we in God's green earth to not say that Smilodon would use its tounge to clean its long sabers? Of course most mammals don't show their teeth. But perhaps the enamel of Smilodon is stronger than the enamel of modern cats. Also, if Smilodon did have lips, it would have been an obstacle to its killing canines. Bulldog Smilodon my ass. I mean, who are we to compare the teeth of prehistoric apex predators with our weak, delicate teeth? Perhaps prehistoric apex predators had much stronger enamels than the modern predators we have today. Its saddens me to think that people would turn majestic creatures like Smilodon into members of a freak show! I agree that some large, predatory dinosaurs had feathers, but to give them lips would make them look like drawbacks from the 1950's! Perhaps, in life, T-rex would endlessly regrow its teeth like a shark! Perhaps there would be evidence for it!

Duane Nash said...

Nice ummm "points" people.

@babehunter1324 "focusing mostly on Smilodon might be somewhat problematic" Yeah I see where you are coming from. It is bound to happen though being the seeming gold standard of sabertooths and more or less the T. rex of the group. As several have pointed out and which I think you are getting at is that "pockets" might be an ideal solution for the more moderate canine genera as well as those with mandibular flanges. Smilodon being the oddball of the groups

@ Carliro I actually did a lot of looking into that Monodelphis dimidiata. I could not find any unequivocal pictures of canines jutting out. This paper argues that it is showing incipient "sabertooth: attributes:
However this paper counters those arguments:
the latter paper arguing convincingly that the large fangs are a sexual characteristic of males and not adapted for hunting large prey.
I am open to new thought on the matter though.

"thylacosmilids are not marsupials" thanks guilty as charged - I'll own it - I guess they are close but not quite true marsupials.

@D-man I thought about mentioning them and I think in my earlier post Jerzy likened them to what Homotherium may have been doing. At first I was down on pockets as I did not know how the exaptation allowing such a structure might occur BUT if clouded leopards do indeed go with pockets I am really starting to get swayed in that direction more and more.

Duane Nash said...

@ D-man "like Duane said the flange supported a thick piece of skin for the saber to slide against" Actually I might be wrong ( I always reserve the right to be wrong), As shown in the alternative "more felid" version that I recently attached to the post an extensive lower lip structure is not actually needed:

Anyways my thinking on these issues is certainly changing and evolving and I applaud the multiple lines of evidence and suggestions people are bringing forth. This was the aim I always had for this blog. Pretty much group sourcing scientific research and ideas!! Thanks very happy with all the effort people are putting in. Not just in correcting my mistakes but in bringing in actually better suggestion than what i first offered, couldn't be happier!!

D-man said...

Yet despite this some people still do not like your hypothesis.

"Its saddens me to think that people would turn majestic creatures like Smilodon into members of a freak show! I agree that some large, predatory dinosaurs had feathers, but to give them lips would make them look like drawbacks from the 1950's! Perhaps, in life, T-rex would endlessly regrow its teeth like a shark! Perhaps there would be evidence for it!"

"Well perhaps some teeth are more immune to dental erosion to others. Smilodon's long sabers must have been too strong to erode and decay while exposed. Hopefully someone would disprove the whole bulldog cat nonsense."


D-man said...

To CoreyStudios2000

"Who are we in God's green earth to not say that Smilodon would use its tounge to clean its long sabers?"
Even when the animal is sleeping? Duane already pointed that out.

"Also, if Smilodon did have lips, it would have been an obstacle to its killing canines."
You do realize that saber tooth cats wrestled their prey into submission and once they do that, they can take their own sweet time to pull up those lips and stab them into the prey's neck.

"Perhaps prehistoric apex predators had much stronger enamels than the modern predators we have today."
So thin long sabers are now more durable than shorter, stouter canines? You do realize that studies have show that if Smilodon were to shake its head back and forth when it stabbed its canines into prey, the canines would snap, which means the animal could then not hunt.

"Its saddens me to think that people would turn majestic creatures like Smilodon into members of a freak show!"
In the words of the great Trey the Explainer: "Science doesn't care what you think about so just admire the beauty." You seem to have way to much nostalgia.

CoreyStudios2000 said...

Oh, and what do you think he might come up next? Smilodon having floppy ears and dropping eyes like a blood hound?

CoreyStudios2000 said...

Honestly, I am writing a science fiction novel that includes Smilodon and already the lip theory is my depiction inaccurate. Has science become some kind of fashion show lately. I bet you're quoting Trey the Explainer just because you people are so fixated on vain statements like "but mommy, what if the pussy cat's teeth get broken?" This blog might eventually be debunked just as young earth creationism, flat earth, the illuminati, and ancient aliens have all been debunked!

babehunter1324 said...

Not Corey, science hasn't became a fashion show now, science has always been changing to try to give the best possible answer to our surroundings.

Well to be fair this theory hasn't been reviewed so far in an academic level, but the information provided checks out, Andrea Cau himself agreed that since Machairodont fans were mostly covered of enamel they likely needed to be kept a high level of moist.

CoreyStudios2000 said...

I honestly doubt still there is any actual hard evidence to conclude that Smilodon had drooping lips like a bloodhound. Already, I can sense that people are becoming more scientifically illiterate. I bet if people accept this, someone might then conclude that Smilodon is actually a harmless, dumb dog and that the earth is flat and 6000 years old. Seriously, I can't stand ignorance!

D-man said...

So you think those big lips on Smilodon, which, may I remind you, Duane never said looked like a bloodhound and instead just an expansion of the normal cat lip, is ludicrous, yet you don't think these lips are ludicrous?

Compared to these examples of the versatility of the mammalian lip, lipped Smilodon looks primitive, and before you say it, the trunk of an elephant, tapir, and Macrauchenia are a fusion of the upper lip and nose.

Plus, Duane is leaning more towards pockets in saber tooth cats (I think).

D-man said...

Like this.

CoreyStudios2000 said...

Thing is that saber-tooth cats have been extinct for 10,000 years. Perhaps the lip theory is possible for members with smaller sabers than smilodon, but Smilodon itself would have evolved a kind of enamel on its sabers immune to weather erosion and that it constantly used its toungue to clean them with saliva, even when sleeping (I sometimes drool while sleeping, which is embarassing, but whatever). So there will come scientific evidence that will debunk this whacked of theory of Duane's. Perhaps a mummified corpse of a Smilodon is all we need to end this pointless debate! Like I said, its NOT like a fashion contest not stop treating it like it, god dammit!

CoreyStudios2000 said...

I agree. That might be enough to expose Duane!

D-man said...

Look, I am in no mood to argue right now, so let me just rap this up quickly. 1) Did you not look at all my examples of the versatility of the mammalian lip and second, Duane Nash is also (maybe?) leaning towards pockets in the lips. Lip pockets are found in other mammals, so it would make sense.

"I agree. That might be enough to expose Duane!"
What's that suppose to mean?

CoreyStudios2000 said...

Just to let you know, Duane's "Grubby" Smilodon lip theory may just be a hoax easily debunked by either examination of the saber teeth by professional scientists or the discovery of a well preserved mummy/cave painting. Until then, we'll wait. And slso to note, Duane is NOT a professional scientist and neither are other hoax masters like that smug faced Protestant creationist Ken Ham.

Christian Halliwell said...

Yeah, it may be debunked in the future, but that's what happens in science. And yeah, Duane is not a palaeontologist, but he backs up his theories with evidence. I must admit I am not entirely convinced by this theory (at least for Smilodon, "pockets" in other sabretoothed predators actually make a lot of sense to me), but it is certainly a possibility, and he may well be right about this. I don't know how many times I'm going to have to tell people like you this before it finally sinks in, you need EVIDENCE to argue with evidence-based theories like this. You do not use evidence, but simply say, "this can't be correct, because I don't like how it looks!" The same absurd "argument" that people use to say that birds aren't dinosaurs or that Tyrannosaurus didn't have feathers. Might the enamel of Smilodon have been able to withstand constant exposure? Yes, that is possible, but there is no evidence to suggest that, and, as it hasn't happened in any other animal, there is no reason whatsoever to think that is the case in Smilodon. So, come back when you actually have some evidence to back up your claims.

babehunter1324 said...

@Corey Are you aware of what a hoax means in science? A hoax in science means that you lied in the conclusions or methodology in a scientifc paper for publicity or monetary gain. How can an entry in a blogpost be considered a "hoax", it is not a published theory though with any luck somebody may study the possibilty in the future. Scientific advance is based on trial and error, formulating theories based on the best available data and change them if a better explanation for a phenomenon exist. For starters Andrea Cau, a carrier paleontologist did support Duane Nash theory on the basis that the canines on machairodonts have an structure that is consistent with that of an animal which teeth are not exposed to the elements.

So you better say something constructive or start to provide evidence against Duane Nash hypothesis or you would rightlfully be blocked by the author.

Carliro said...

CoreyStudios2000, just shut the fuck up. You resort to ad hominems, circular logic and just petty insults to defend your fetish for classical depictions. You're having a rather irrational response because you refuse to accept research.

@Duane Nash: Interesting. I do think more studies need to be made on M. dimidiata (and Monodelphis opossums in general), but a primary role in sexual selection over predation seems likely.

D-man said...

CoreyStudios2000 You have gone far enough, comparing Duane Nash to nonsense creationists is just plain rude and mean. Cry all you want, it won't matter. The versatility of the mammalian lip and the claims that Duane made are enough to support the fact that saber tooth had covered canines. I am dropping this conversation because of your stubbornness and the fact you will never except it.

D-man said...

So lets recap, we have....

Bulldog lips:

Elongated cat lips:

Lips over sabers:

And now Canine Sheaths:

CoreyStudios2000 said...

I'm not crying here, good sir. I am just stating that have been NO terrestrial predators alive today like Smilodon that we can compare to. So this post may as well be just speculation. Forgive me for being a bit harsh, but I noticed that Daune was saying "come at me bro," so it's more reason to believe him less. One day someone will find proof of Smilodon having more evolved enamel than modern cats and put this argument to rest. Honestly, author is acting more like a show off hipster than a true professional.

D-man said...

That is just to draw attention towards the post, and maybe you are ignoring the fact that someone already said Andrea Cau, a professional paleontologist, said the structure of the tooth resembles that of an animal with covered teeth. Science is not trying to turn this into a fashion show, you are just interpreting it as such.

CoreyStudios2000 said...

That would take more than one agreement from one paleontologist to convince me of anything radical and perhaps overspeculative as this. I bet that in life, Smilodon's teeth were too strong and specialized to even erode so easily as the weaker teeth of modern big cats. What if it needs those fangs to attract mates? How can a Smilodon with slobbery, bulldog lips even possibly help in getting a female to his dominance? Argue as much as you want, but Danue's argument obviously comes to this same, mocking conclusion in his lip theory:

D-man said...

Would display devices have literal serration in them?

CoreyStudios2000 said...

In that case, Smilodon's teeth would have served both. Also, the lips would have been an obstacle to the fangs, not a benefit.

Christian Halliwell said...

@CoreyStudios2000 "That would take more than one agreement from one paleontologist to convince me of anything radical and perhaps overspeculative as this." Yeah, saying it had elongated lips to cover its sabres is totally more radical and speculative than saying they had developed stonger enamel, something which has NO basis in fossil evidence whatsoever.

"What if it needs those fangs to attract mates? How can a Smilodon with slobbery, bulldog lips even possibly help in getting a female to his dominance?" You know there's this amazing thing called "baring teeth". Cats do it all the time. As for "slobbery bulldog lips," big cats like lions "slobber" quite frequently, as do the majority of large mammals.

"I am just stating that have been NO terrestrial predators alive today like Smilodon that we can compare to. So this post may as well be just speculation." Wow, you really dug your own grave with this sentence... If this theory "may as well be just speculation," because there is no living analogue (which actually might not even be true...), then the same goes for any argument for uncovered sabres.

"One day someone will find proof of Smilodon having more evolved enamel than modern cats and put this argument to rest." Maybe they will, maybe they won't. That's the thing about science, unexpected things are discovered all the time and you can't predict it. But in the mean time, we need to use what is known already to back up our arguments and reach a conclusion as to what these animals were like. You have not used any evidence whatsoever to back up any of your claims (and stubbornly insist on continuing not to do so), so you are welcome to go "grumble quietly in a corner, clutching your VHS copy of Jurassic Park," so long as you stop wasting the valuable time of people who actually do.

CoreyStudios2000 said...

I found a link concerning this, so maybe I can get more support from it.

Duane Nash said...

Glad I was at work when all this went down above. Thanks to those that defended me and everything holding down the fort. I do have to laugh a bit imagining Smilodon constantly licking its canines. Waking up all the time to lick its canines. Sort of something porny about that image too... Yeah I could delete Corey as he has spammed me a bunch... BUT I find him kinda cute. Plus he represents the small lip contingent. If I was for something and saw that this knuckledhead was for the same thing I was for I would leap to other side!! Hopefully he will bring me more believers for my neo-hipster-psuedoscience-rant-o-speculations.

babehunter1324 said...

Are you aware that a lot of animals had sexual selective traits that we found disgusting or ugly but are attractive for other members of the species, right?

Go no further than the Warthog, those ugly bumps on it's head are used for display to some extent.

Anyhow, modern felides barelly ever use visual sexual display to attract females they tend to use roars for territorial demarkation as well as scent, also considering that a lot of species of Machairodonts like Smilodon had a relativelly small sexual dimorphism (there was some according to the latest research but it was about as much as in the snow leopard, the least sexually dimorphic big cat) and that the very few times we had direct evidence of associated Smilodon remains they appear in more or less gender equal proportions it is quite clear that if Smilodon was social it di thing svery differently to modern lions.

The funny thing about this is that we wouldn't had this conversation had not Smildon be the "choosen one" just because it's popular, the fact that nearly every other Machairodont had low jaw flanges about as long as their canines means that they if the had sheathed teeth they certainly had a clouded leopard like solution. Smilodon is the outlier and the only one I can think off that breaks the mould.

babehunter1324 said...


I might not be 100% convinced with your original bulldog Smilodon reconstruction, but at least you gave a lot of information to support it to the point that it's clear that the hypthesis grants further research, it might be right, it might be wrong but it is grounded in logic thinking.

Meanwhile @Corey arguments are based on fallacies and aesthetics and in the BELIEF that new research will proof the hypothesis is wrong, since he isn't the one that brings any scientific arguments to the discussion, why would any animal care about looking cool or threatening to modern humans? Heck Smilodon only coexist a few thousand years with humans before it's extinction.

So in a very ironic way, Corey compared Duane to creationist when the ones who's argument is based on beliefs, personal preference and no physcial evidence is Corey. He is behaving like the very same thing he loathes...

Duane Nash said...

@babehunter1324 Interesting thoughts. My mind changes and moves on these issues all the time. Anyone has a right to change their mine with new and better arguments and evidence. Even if it means throwing your own idea in the scrap heap. Case in point pockets make sense for most sabertooths and I don't think the flappy lips I first drew with the upper lip plopping down against the lower lip is the best option anymore for smilodon and am favoring the depiction I recently added that is more classically felid by Unilorg. That is the way things should be allowed... not undying dogmatism.

@Corey because I am sure he'll back as he is compiling a massive campaign against this. Enough picking on him as it is starting to look like child abuse. And I just got off the phone with Ken Ham who happens to agree with all his arguments so he has proponents for his saber licking kitty.

Duane Nash said...


CoreyStudios2000 said...
This comment has been removed by the author.
CoreyStudios2000 said...

Accusing me of creationism, are you. I can assure you that creationism should be banned! Honestly, this is exactly we are losing the science war to China! I for one see Ken Ham as a parasite and he ought to go back to Australia! I for one actually support evolution and I am making drawings for my novel. Now I have to remake them and make Tyrannosaurus look like a lizard because now I am going to be made fun of for being "obsolete"! I feel pissed off that Duane is enjoying himself like a king on a throne.

babehunter1324 said...

I'm not accusing you of being a creationist, but of being just as dogmatic as them and saying things are wrong because they don't fit in your preconceived set of ideas.

That's not how science works. Science should always strive to found the best possible answer to natural phenomenons. It doesn't matter if a hypothesis is flawed since both confirming it and DENYING it allow us to progress further in our scientific knowledge. If it was for people like you we might be still stuck with Newtonian physics or classic Darwinian evolution just because they were good enough to explain a lot of natural phenomena. Even if Duane Nash won't publish his findings in an academic level it might inspire somebody to do it in the future.

I grow with Mauricio Antón reconstructions of Machairodontids, yet I have no problem conceiving the possibility that they might not be accurate nor does it undermine my oppinon in his abbilities as a paleoartist, that would be like saying Charles R Knight was a bad paleoartist because it's work is outdated.

babehunter1324 said...

Really should stop feeding the troll...

thiago chagas said...

Actually it would not need such lips. Mammals have a thicker layer of enamel than crocodiles, for example, and that is why they can live without constantly replacing their teeth. Saliva itself does not help tha much to remineralize the teeth (otherwise we would not have to brush our teeth and lions, tigers, bears, wolves and hyenas, for example, would not show yellowish teeth when they reach adulthood), so having exposed teeth would not be a problem.

Christian Halliwell said...

Yeah, stop feeding the trolls...

D-man said...


Carliro said...

Here's my two cents on thylacosmilids and their "tusk-like" sabers:

Mr. Strong said...

Well I'm a little late to the party on this one by the look of things, I just found your blog and will say I enjoy it so far.

I really can't say I know much of anything about Saber tooth animals in general (generally any rea, but it's pretty hard to avoid some of the more popular science on Smilodon since it's kind of a paleo mascot like the Tyrannosaurus or Triceratops.

From everything I've seen on the Smilodon though, I always find it frustrating because the feeding mechanics (or I guess more specifically the killing mechanics) as I've seen them proposed make no sense given the build of the creature in general. A heavy built animal that delivers precise bites with fragile teeth and to very large creatures doesn't really track imo. To me it makes more sense if it was a head butter or I guess chin-stabber might be more accurate -- using its neck muscles to drive in a piercing blow rather than finagling itself into such a place where it can simultaneously subdue large prey items while delivering a death stroke. (I feel as though I've seen this proposed somewhere, but I can never for the life of me find anything while searching for it.)

So I was a bit skeptical at first, but honestly thicker lips (particularly on the lower lips) make a lot of sense not only for saliva purposes, but also protecting them from breakage when struggling with prey. Everything I've seen about Smilodon teeth is that they're very vulnerable to breaking when put under stress perpendicular to the tooth. Having a thick lip might have even helped absorb some of the force from struggling prey to help keep the canines from breaking.

A chin-smacking saber would also spend most of its time with its sightline perpendicular to its target, but a well developed set of lips and whiskers could allow the saber to keep a strong sensory connection with prey, even while being unable to look at it directly. The wiki article anyway says that the sensory capabilities in feline whiskers help with 3 dimensional awareness, so it would make sense that a saber could be using lips and whiskers to find a good time and place to throw opportunistic strikes against the belly, neck, back, or even legs while pride mates struck at other locations around the prey animal.

It doesn't even need to be able to pull its lips up particularly far. Just far enough to clear the chin and let the sabers hang out.

LeonelSaberTooth said...

Hello, ive read the whole thing,
About the topic you have been covering, first of all, if they did have long lips which cover the fangs it would be, like the comments above, very biteable. Second of all in order for the cat to expose his canines to bite anything it would need the lips to have muscles in them, if muacles were built in the lips it will be seen in the skull (skull shows where muscles touched it) and based on my ressarch no skull indicates this kind of lips. Another reason which i can't really explain is that it will simply be too heavy, and the lips would need to change the whole anatomical structure of the head and snout muscles to support their weight. You have mentioned something about teeth that chew and slice meat need to be covered with saliva, most articles claim that smilodon didnt use his upper fangs for eating at all, that is why hia incisors and other teeth need to be so large as well, he probably only used his canines to kill prey. Another suggestion is that the fangs were constantly licked (yes, licked) with the saber cat tongue to keep them wet, much like some lizards lick their eyes conatantly.
Correct me if i am mistaking and sorry for bad english, have a good day and thanks for reading :)

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