Dinosaur lips?

[stargatedalek]

Anatomy trumps genetics, and behavior trumps anatomy.

If we want to use genetics for every inference we should be reconstructing all dinosaurs with either full coats of feathers and bills or with armored crocodilian scutes. Similarly if we use solely anatomy for every depiction all dinosaurs should be flat. A certain degree of inference is required in reconstruction, and this means cross referencing an animals probable (or in some rare cases proven) behavior with its preserved anatomy to interpret a realistic appearance, then using genetics only to fill in the unknowns after that.

Crocodiles have exposed teeth for very specific reasons. It has nothing to do with the sensory organs on their snouts, crocodiles have exposed teeth because they spend the vast majority of their time with their teeth underwater. A land-based animal can't do this without its teeth being damaged by exposure to the air, we see this in tusked mammals, but not in dinosaurs. And in case someone thought they were going to be smart, most fish don't have exposed teeth because it makes them less hydrodynamic, which is unimportant for an ambush predator like a crocodile.

I'm no longer going to directly reply to anyone who just suggests crocodiles were the best reference for Tyrannosaur anatomy because Suchomimus has a skull superficially and convergently similar to crocodiles in profile shape. I'm low enough on aspirin as-is.

You yourself mention tusks immediately before discounting a similar possibility in dinosaurs. The truth is that there are, in fact, several types of animals that have exposed teeth, and while it's uncommon, it's clearly possible. I'm very much in the camp that exposed teeth were an archosaur peculiarity, and until there is clear, unequivocal evidence one way or another, I feel it's safer to infer a lack of lips, just like most find it safe to infer some kind of plumage on tyrannosaurines.

Tusks don't need to maintain the state of small serrations or sharp edges. Tusks become worn and damaged from exposure to the air, some animals manage to maintain sharp points by sharpening them, but that's the absolute best they can do. If dinosaur teeth were exposed they would need to be replaced near constantly in order to maintain their function.

The only animals with exposed teeth are either aquatic, or have heavily modified teeth that they don't use for traditional purposes.

Thanks, ironically I was just reading an article from Mark Witton's blog from 2016 where he is still open to the idea that some theropods could have been lipless. He raises the question that I did earlier here about toothy Pterosaurs and he also brings up the interesting fact and I quote "that several crocodylians species 'hibernate', or more accurately aestivate, for months at a time in dry underground burrows during the hottest summer months (Grigg and Kirshner 2015). During these intervals they do not access water at all. Other, South American species spend dry spells as fully terrestrial carnivores, abandoning aquatic habits and obtaining water largely from the prey they kill (Grigg and Kirshner 2015)."
I haven't finished the article yet.

Crocodilians also don't have serrations to worry about. Their teeth are peg-shaped, smooth with a sharp point, dinosaur teeth are serrated and have precision edges.

[EarthboundEiniosaurus]

Very good point about the serrations stargatedalek! I hadn't thought about how incredibly specialized mammalian tusks are, even those that do retain enamel on some surfaces. [Edit] also this (credit to David Evans on twitter) Caiman, Komodo dragon, Gorgosaurus and Daspletosaurus maxilla

[Doug Watson]

Crocodilians also don't have serrations to worry about. Their teeth are peg-shaped, smooth with a sharp point, dinosaur teeth are serrated and have precision edges.

You mean those serrations that would be constantly clogged with fresh moist blood and flesh from the last meal? 

[Cloud the Dinosaur King]

Crocodilians also don't have serrations to worry about. Their teeth are peg-shaped, smooth with a sharp point, dinosaur teeth are serrated and have precision edges.

You mean those serrations that would be constantly clogged with fresh moist blood and flesh from the last meal? 

That's a good thing as this would help some theropods have a more infectious bite.

[Lanthanotus]

Woah, hot debate here, so this formal question may seem a bit lame....

.... I read the better part of the text and after not finding what was so hotly debated here I did a search for the term within the text, but I could not find any quote about the specimen in question having lips or not. What I could read/find was, that the specimen in question would have had a crocodile like facial sensory system and scales around the mouth.

This however does not disprove lips per se (as scales and lips can co-exist) and more important, while the imaged reconstruction is lipless, this could be a default choice because it is more common these days to reconstruct theropods without lips rather than with. After all, the author does not specifically state that the specimen was lipless - or I must totally have missed it, but please feel free to point the quoted text out to me.

[The Atroxious]

That's a good thing as this would help some theropods have a more infectious bite.

Except that the infectious bite idea has rapidly lost ground in recent years, assuming you're referring to the concept that bacteria in a predator's mouth would significantly weaken it's prey. Relying on an infectious bite as a hunting strategy is rather impractical due to the time it would take for the wound to fester, and is better explained by possession of venom, or blood loss from the bite.

[Cloud the Dinosaur King]

That's a good thing as this would help some theropods have a more infectious bite.

Except that the infectious bite idea has rapidly lost ground in recent years, assuming you're referring to the concept that bacteria in a predator's mouth would significantly weaken it's prey. Relying on an infectious bite as a hunting strategy is rather impractical due to the time it would take for the wound to fester, and is better explained by possession of venom, or blood loss from the bite.

I get that.

[stargatedalek]

Crocodilians also don't have serrations to worry about. Their teeth are peg-shaped, smooth with a sharp point, dinosaur teeth are serrated and have precision edges.

You mean those serrations that would be constantly clogged with fresh moist blood and flesh from the last meal? 

Exactly, being able to close them inside the mouth aids in cleaning ones own teeth of debris. Meat doesn't get the chance to become caked on and can be "swished" out of crevices and serrations using saliva, this is why crocodilians rely on birds to clean their mouths (gums mostly) even without serrations.

That's a good thing as this would help some theropods have a more infectious bite.

Except that the infectious bite idea has rapidly lost ground in recent years, assuming you're referring to the concept that bacteria in a predator's mouth would significantly weaken it's prey. Relying on an infectious bite as a hunting strategy is rather impractical due to the time it would take for the wound to fester, and is better explained by possession of venom, or blood loss from the bite.

The idea of an infectious bite was based on the idea that some monitor lizards possessed it, which has since been debunked. If an extinct animal had an infectious bite it was an entirely "new" adaptation, no modern animal has one.

*edit*

Woah, hot debate here, so this formal question may seem a bit lame....

.... I read the better part of the text and after not finding what was so hotly debated here I did a search for the term within the text, but I could not find any quote about the specimen in question having lips or not. What I could read/find was, that the specimen in question would have had a crocodile like facial sensory system and scales around the mouth.

This however does not disprove lips per se (as scales and lips can co-exist) and more important, while the imaged reconstruction is lipless, this could be a default choice because it is more common these days to reconstruct theropods without lips rather than with. After all, the author does not specifically state that the specimen was lipless - or I must totally have missed it, but please feel free to point the quoted text out to me.

And this is really the most that this is evidence of (if these aren't just preservation artifacts).

[Sim]

They openly admit to only bothering to make comparisons to crocodiles. There is not one bit of mention of the animals being of entirely different ecological niche, nor of other animals that display similar patterns.

Actually, none of this is correct.  In the paper that names Daspletosaurus horneri, the authors address each of these points.  It's in the Soft tissues section under Results and in the Soft tissue interpretations section under Discussion.

Woah, hot debate here, so this formal question may seem a bit lame....

.... I read the better part of the text and after not finding what was so hotly debated here I did a search for the term within the text, but I could not find any quote about the specimen in question having lips or not. What I could read/find was, that the specimen in question would have had a crocodile like facial sensory system and scales around the mouth.

This however does not disprove lips per se (as scales and lips can co-exist) and more important, while the imaged reconstruction is lipless, this could be a default choice because it is more common these days to reconstruct theropods without lips rather than with. After all, the author does not specifically state that the specimen was lipless - or I must totally have missed it, but please feel free to point the quoted text out to me.

Not lame at all.  I think what you've said is very relevant.  I also didn't find anything about lips in the paper.  I find what the authors suggest about the integument interesting, although I'd like to see what other palaeontologists think about it.


Personally, I think the teeth being covered when the mouth is closed in animals as different as squamates and mammals suggests an animal's teeth would only be exposed if this was advantageous, rather than just because they belong to a particular group.  As Mark Witton mentioned in his excellent blog post here there is an extant cetacean that doesn't have lips, the (very unusual) South Asian river dolphin.  It's a lipless member of an otherwise lipped group.  I think this is more evidence that shows an animal's teeth will be exposed if it's advantageous, rather than because an animal is placed by people in a particular group.

This new paper only comments on the facial integument of tyrannosauroids, it doesn't say anything about the facial integument of other non-avian theropods.  Given how much difference there is among theropods in skeletal anatomy, integument, diet, ecology and in particular dentition, I would expect some theropods to have exposed teeth and some to have covered teeth when their mouth is closed.  I would consider each theropod type/group individually with regards to this matter.

[CrypticPrism]

They openly admit to only bothering to make comparisons to crocodiles. There is not one bit of mention of the animals being of entirely different ecological niche, nor of other animals that display similar patterns.

Actually, none of this is correct.  In the paper that names Daspletosaurus horneri, the authors address each of these points.  It's in the Soft tissues section under Results and in the Soft tissue interpretations section under Discussion.

Woah, hot debate here, so this formal question may seem a bit lame....

.... I read the better part of the text and after not finding what was so hotly debated here I did a search for the term within the text, but I could not find any quote about the specimen in question having lips or not. What I could read/find was, that the specimen in question would have had a crocodile like facial sensory system and scales around the mouth.

This however does not disprove lips per se (as scales and lips can co-exist) and more important, while the imaged reconstruction is lipless, this could be a default choice because it is more common these days to reconstruct theropods without lips rather than with. After all, the author does not specifically state that the specimen was lipless - or I must totally have missed it, but please feel free to point the quoted text out to me.

Not lame at all.  I think what you've said is very relevant.  I also didn't find anything about lips in the paper.  I find what the authors suggest about the integument interesting, although I'd like to see what other palaeontologists think about it.


Personally, I think the teeth being covered when the mouth is closed in animals as different as squamates and mammals suggests an animal's teeth would only be exposed if this was advantageous, rather than just because they belong to a particular group.  As Mark Witton mentioned in his excellent blog post here there is an extant cetacean that doesn't have lips, the (very unusual) South Asian river dolphin.  It's a lipless member of an otherwise lipped group.  I think this is more evidence that shows an animal's teeth will be exposed if it's advantageous, rather than because an animal is placed by people in a particular group.

This new paper only comments on the facial integument of tyrannosauroids, it doesn't say anything about the facial integument of other non-avian theropods.  Given how much difference there is among theropods in skeletal anatomy, integument, diet, ecology and in particular dentition, I would expect some theropods to have exposed teeth and some to have covered teeth when their mouth is closed.  I would consider each theropod type/group individually with regards to this matter.

River dolphins are aquatic and piscivorous, so it's a bad analogue.

[Lanthanotus]

[...]

River dolphins are aquatic and piscivorous, so it's a bad analogue.

It may be a bad analogue, but there's a valid point about it....

... the default trait of vertebrate animals over all classes seems to be, that mouthes can be shut tight, rendering the dentition hidden behind some form of "lips" or better to say, some sort of tissue that protects the dentition from UV light and climate conditions which have a highly decaying effect on teeth.

Have a look through all the species of fish, amphibians, reptiles, birds and mammals and you'll find only a "handfull" of species in which parts of the dentition can be seen once the mouth is fully closed. Now have an even closer look to sort them out for terrestrial and aquatic animals.

The way greater ammount of species with open dentition lives an aquatic or mainly lifestyle.

For terrestrial animals there's only a few species with parts of their dentition being open when the mouth is fully closed and in almost every case those teeth did evolve as some sort of display or sexual dimorphism (porcupines, elephants, cervines) and are only secondarly used for purposes of feeding. In these cases the dentition lays never fully open but this affects only a few, very specialised teeth, most times just two.

A second, even smaller group of terrestrial animals has parts of their dentition laying open and this teeth are primarily used for biting. These animals are all rodent species and dwell the better part of their life underground, in dark and moist conditions.

That being said, the recent kingdom of animals does not provide a single example for a land dwelling species in which half of the dentition lays open permanently (as is the case in most theropod reconstructions these days, but only since JP I think, weirdly enough just the T. rex had this ridiculous bite, the raptors or frill necks hadn't).

Conclusion: Theropods had "lips" (excepetions may be Spinosauridae).

[ZoPteryx]

Woah, hot debate here, so this formal question may seem a bit lame....

.... I read the better part of the text and after not finding what was so hotly debated here I did a search for the term within the text, but I could not find any quote about the specimen in question having lips or not. What I could read/find was, that the specimen in question would have had a crocodile like facial sensory system and scales around the mouth.

This however does not disprove lips per se (as scales and lips can co-exist) and more important, while the imaged reconstruction is lipless, this could be a default choice because it is more common these days to reconstruct theropods without lips rather than with. After all, the author does not specifically state that the specimen was lipless - or I must totally have missed it, but please feel free to point the quoted text out to me.

THIS

I too read the whole paper, and the relevant portions of the supplement, and found nothing about lips.  If the authors are saying anything about liplessness, it's just their non-peer reviewed opinions.  The closest I found was mention of the gum-line being reminiscent of alligators in that it was largely smooth just above the teeth.  I think, however, that this is matter of opinion.  In photos linked to earlier, the tyrannosaurs' gum-line looked more similar to the Komodo Dragon jaw, which of course has lips.  And of course, anything is going to look smooth compared to the heavily pitted upper portions of the jaw.  They also mention that the patterning of pits is reminiscent of what is seen in some snakes and mammals, which of course have lips.  So these sort of sensors can function in lipped animals.  And as mentioned before, their sample size of extant analogues is not ideal.  I would have liked to have seen some squamates in the lineup, as well as some birds where the beak is restricted to the tips of the jaw, like Turkey Vultures and California Condors.

As per the rest of the paper's suggestions, I really have no problems with them.  It makes sense that tyrannosaurs would have very sensitive snouts, what with their reduced arms, it's really their only way of interacting with their environment; kind of like sharks in that regard.*  You'd want to protect these sensory organs, and what better way to do that than with flattened scales.  Now, I think cornified skin is just as likely, but crocodilians are our only go-to for this sort of thing, so I understand why the authors went the scaly route.**  It's nice we finally have some solid evidence for the bony hornlets on tyrannosaur snouts, no issues there as far as I can tell.

Now the final point.  Figure 4 in the paper, which is the uncolored version of that heavily shrink-wrapped and lipless Daspletosaurus portrait you've seen earlier, has the following caption [emphasis added]:

Figure 4. The craniofacial epidermis of Daspletosaurus horneri sp. nov., based on comparison with its closest living relatives, crocodylians and birds. Bone texture indicates large zones of large, flat scales and subordinate regions of armor-like skin and cornified epidermis; integumentary sense organs occur on the flat scales that cover the densest regions of neurovascular foramina. The region outside of the crocodylian-like skin is reconstructed with small scales after fossilized skin impressions of tyrannosaurids. This figure is not covered by the CC BY licence. Illustration © Dino Pulerà. All rights reserved, used with permission.

Umm, what fossilized skin impressions?!  Are they just talking about those rumored T. rex or Tarbosaurus impressions, or is their something in the published literature that has slipped by us?  And what leads them to assume they're scales rather than the bumps of feather follicles?

And, for the record, I have no problem with them naming it after Horner.  His contributions to paleontology far out weigh his occasional media-inflated oddball theories.  This species represents, the authors claim, confirmation that at least some American tyrannosaurids evolved in via anagenesis (linear evolution), a theory first postulated by Horner.

*In fact, manipulation via the jaws, rather than hands, was probably already standard practice for all bipedal dinosaurs
**Can't check to see if crocodilians really do have facial/snout scales right now, but I'll check Biology and Evolution of Crocodylians tomorrow

[Halichoeres]

For terrestrial animals there's only a few species with parts of their dentition being open when the mouth is fully closed and in almost every case those teeth did evolve as some sort of display or sexual dimorphism (porcupines, elephants, cervines) and are only secondarly used for purposes of feeding. In these cases the dentition lays never fully open but this affects only a few, very specialised teeth, most times just two.

Porcupines? That's news to me! I wasn't aware of any rodents that used teeth for display in this way.

[Sim]

River dolphins are aquatic and piscivorous, so it's a bad analogue.

It isn't a bad analogue for the following reasons:

1. There are other kinds of toothed animals that are, or are thought to be, aquatic and piscivorous, like some theropods.

2. Cetaceans are typically lipped.  That there is a lipless one I think shows more evidence that lips are usually advantageous for an animal (since most cetaceans are lipped).  It also provides evidence that a particular group can contain both lipped and lipless species - I'm not suggesting this is often the case, I'm just saying it shows it's possible.  And I think this is relevant to consider for theropods given the extremely high diversity among them.

... the default trait of vertebrate animals over all classes seems to be, that mouthes can be shut tight, rendering the dentition hidden behind some form of "lips" or better to say, some sort of tissue that protects the dentition from UV light and climate conditions which have a highly decaying effect on teeth.

Have a look through all the species of fish, amphibians, reptiles, birds and mammals and you'll find only a "handfull" of species in which parts of the dentition can be seen once the mouth is fully closed. Now have an even closer look to sort them out for terrestrial and aquatic animals.

The way greater ammount of species with open dentition lives an aquatic or mainly lifestyle.

For terrestrial animals there's only a few species with parts of their dentition being open when the mouth is fully closed and in almost every case those teeth did evolve as some sort of display or sexual dimorphism (porcupines, elephants, cervines) and are only secondarly used for purposes of feeding. In these cases the dentition lays never fully open but this affects only a few, very specialised teeth, most times just two.

A second, even smaller group of terrestrial animals has parts of their dentition laying open and this teeth are primarily used for biting. These animals are all rodent species and dwell the better part of their life underground, in dark and moist conditions.

That being said, the recent kingdom of animals does not provide a single example for a land dwelling species in which half of the dentition lays open permanently (as is the case in most theropod reconstructions these days, but only since JP I think, weirdly enough just the T. rex had this ridiculous bite, the raptors or frill necks hadn't).

Conclusion: Theropods had "lips" (excepetions may be Spinosauridae).

Very good points.  I personally think it seems most toothed theropods would have had lips.  I can't imagine spinosaurids, Masiakasaurus and maybe scansoriopterygids not having exposed teeth though.

[ZoPteryx]

Now, I think cornified skin is just as likely, but crocodilians are our only go-to for this sort of thing, so I understand why the authors went the scaly route.**

**Can't check to see if crocodilians really do have facial/snout scales right now, but I'll check Biology and Evolution of Crocodylians tomorrow

Just checked, here's what the authors have to say:

The surface of the skull is ornamented by bony sculpturing formed by secondary dermal ossifications.  These adhere firmly to much of the bone on the dorsal surface, becoming more complex with age, and very likely strengthening the skull structure.

- Biology and Evolution of Crocodylians, page 113

So I think "secondary dermal ossifications" is just the technical term for scales, as in other sections where the sensory receptors are discussed, they are said to occupy the scales of the head and body (only the former in alligators).

[Lanthanotus]

For terrestrial animals there's only a few species with parts of their dentition being open when the mouth is fully closed and in almost every case those teeth did evolve as some sort of display or sexual dimorphism (porcupines, elephants, cervines) and are only secondarly used for purposes of feeding. In these cases the dentition lays never fully open but this affects only a few, very specialised teeth, most times just two.

Porcupines? That's news to me! I wasn't aware of any rodents that used teeth for display in this way.

Sorry, my mistake (no native English speaker)..... what I ment  were swines, pigs....Porcupine is that spiky rodent, isn't it?

[Halichoeres]

For terrestrial animals there's only a few species with parts of their dentition being open when the mouth is fully closed and in almost every case those teeth did evolve as some sort of display or sexual dimorphism (porcupines, elephants, cervines) and are only secondarly used for purposes of feeding. In these cases the dentition lays never fully open but this affects only a few, very specialised teeth, most times just two.

Porcupines? That's news to me! I wasn't aware of any rodents that used teeth for display in this way.

Sorry, my mistake (no native English speaker)..... what I ment  were swines, pigs....Porcupine is that spiky rodent, isn't it?

Oh, of course. I should have guessed that. Understandable, since "porcupine" comes from French words meaning "spiny pig."

[BlueKrono]

Those French... always confusin' everybody.

[Dobber]

Please forgive my ignorance but wouldn't exposure to constant water flow "weather" teeth faster than exposure to air. Also I thought it was mentioned that the water exposed teeth where conical and not specialized and serrated. What about Sharks? They are constantly exposed and are very sharp and specialized. If I misunderstood the point that was trying to be made then my apologies.

[stargatedalek]

Please forgive my ignorance but wouldn't exposure to constant water flow "weather" teeth faster than exposure to air. Also I thought it was mentioned that the water exposed teeth where conical and not specialized and serrated. What about Sharks? They are constantly exposed and are very sharp and specialized. If I misunderstood the point that was trying to be made then my apologies.

It's more than just weathering, reaction to air causes degradation of enamel, not exposure to "the elements" per-se. Whereas any water current strong enough to wear away at enamel any more than saliva would is coming close to rending the animals flesh.