Dinosaur lips?

[Patrx]

I do agree with Carr that tyrannosaurids did not have "lips" covering their teeth when their mouths were closed.

Why's that? For now, I find myself siding with Witton with regard to the "lips" conversation, but this is one case where I can't even pretend to be free from bias, so take my word with that in mind! Theropods just look so darn ugly to me with their teeth exposed like crocodylians'  But, the issue keeps being debated and going back and forth - I do hope that someday there will be some degree of consensus about it, one way or the other. I'll follow where the science leads, of course.

[John]

I do agree with Carr that tyrannosaurids did not have "lips" covering their teeth when their mouths were closed.

Why's that? For now, I find myself siding with Witton with regard to the "lips" conversation, but this is one case where I can't even pretend to be free from bias, so take my word with that in mind! Theropods just look so darn ugly to me with their teeth exposed like crocodylians'  But, the issue keeps being debated and going back and forth - I do hope that someday there will be some degree of consensus about it, one way or the other. I'll follow where the science leads, of course.

It's just the way the skulls are formed that makes me doubt the "lips" hypothesis.But of course,new discoveries can always change my mind.Who knows what will be discovered tomorrow?

And yes,I can see how theropods could be called ugly,especially with exposed teeth making them really look vicious.But to me,they would still look no less dangerous with completely covered teeth.That Mark Witton T. rex profile shows something I would never want to run into...

[Sim]

It's an interesting blog post.

A related issue concerns a possible link between extra-oral tissues and foramina counts. Morhardt (2009) noted that, as a general rule, extant animals with average foramina counts below 50 in each jaw bone have tooth-covering extra-oral tissues; that those above 50 but below 100 have immobile facial tissues; and only those with 100 or more are reliably excluded from having lips or other means of tooth coverage.

In response to the above quote from the blog post, I've noticed the South Asian river dolphin (Platanista gangetica) has exposed teeth even when its mouth is closed, but its jaws appear to be very much lacking in foramina.  So it appears the general rule from the above quote doesn't apply to this dolphin species, which then leads me to think, just how far does this "general rule" really apply?

[stargatedalek]

I'm reminded of a certain "devil" by that image, the scutes and especially the snout covered with armor/scutes/spikes/whatever. Unconscious maybe, but I can't help feeling there was definitely some influence.

[tyrantqueen]

I'm reminded of a certain "devil" by that image, the scutes and especially the snout covered with armor/scutes/spikes/whatever. Unconscious maybe, but I can't help feeling there was definitely some influence.

The Jersey Devil?

[Patrx]

It's just the way the skulls are formed that makes me doubt the "lips" hypothesis.But of course,new discoveries can always change my mind.Who knows what will be discovered tomorrow?

Fair enough! I think this area of research is going to yield a lot of interesting data in the future.

But to me,they would still look no less dangerous with completely covered teeth.That Mark Witton T. rex profile shows something I would never want to run into...

Definitely. After all, modern carnivorans have covered teeth, and they can be very intimidating.

[Minmiminime]

Finally! I was waiting for a reconstruction based on that paper

The Carr et al. (2017) tyrannosaur paper? This is more in-response to that paper than based directly on it. Also relevant is Barker et. al (2017) regarding the facial anatomy of Neovenator. According to Mark:
"...there is another version of this text that goes into a little more detail - Barker et al. are mentioned there. The plan is to turn this into a more formal response at some point".

Yes, this reconstruction builds on that very nicely I'm always cautious when a paper asserts that something must have been the case; Witton is very good at remaining grounded, rational, constructive, and yet, creative in the face of them. I haven't seen the other paper! But I was surprised at the time that the "horns on the cheeks" thing mentioned in Carr's wasn't picked up on, because that's something that hasn't been shown in most restorations. It's a very, very good illustration, I like it a lot!

[HD-man]

I do agree with Carr that tyrannosaurids did not have "lips" covering their teeth when their mouths were closed.

Why's that? For now, I find myself siding with Witton with regard to the "lips" conversation, but this is one case where I can't even pretend to be free from bias, so take my word with that in mind! Theropods just look so darn ugly to me with their teeth exposed like crocodylians'  But, the issue keeps being debated and going back and forth - I do hope that someday there will be some degree of consensus about it, one way or the other. I'll follow where the science leads, of course.

It's just the way the skulls are formed that makes me doubt the "lips" hypothesis.But of course,new discoveries can always change my mind.Who knows what will be discovered tomorrow?

That reminds me of this Witton quote in general & the bolded part in particular:

Significantly, I can't find any tyrannosaurid skulls where these possible scale correlates extend right to the base of the maxilla (see photos, above). Rather, they terminate a few centimetres above the line of labial foramina, and this might have bearing on ongoing discussions about dinosaur lips. Scleroglossan lizards (the group that includes geckos, skinks, varanoids and amphisbaenians) frequently have osteoderms on their faces which cover their snouts (including the maxillae) except for a region around the labial foramina, which is smooth. This seems to relate to the presence of lip tissues displacing the scales from the skull and prohibiting formation of a epidermal correlate adjacent to the toothrow. Their maxillary juxtaposition of epidermal correlates is the same configuration that we see in tyrannosaurids as well as a number of other non-avian dinosaurs with maxillary epidermal correlates (e,g, pachycephalosaurids, ankylosaurids, some ceratopsids) and this has to be regarded consistent with hypotheses of extra-oral 'lips' in tyrannosaurids and other dinosaurs. If we add this to the evidence from foramina counts (Morhardt 2009, also see above) as well as other arguments for extra-oral tissues the case for crocodylian-like exposed teeth is looking increasingly doubtful. I must admit to thinking that proponents of exposed dinosaur teeth really need to start making better cases for this idea: most ways we can slice this particular debate suggests that extra-oral tissues are looking likely (and no, the common argument that their teeth were too big to be sheathed isn't valid: it's simply a speculation based on incredulity, not actual data from dinosaur skulls).

[John]

I do agree with Carr that tyrannosaurids did not have "lips" covering their teeth when their mouths were closed.

Why's that? For now, I find myself siding with Witton with regard to the "lips" conversation, but this is one case where I can't even pretend to be free from bias, so take my word with that in mind! Theropods just look so darn ugly to me with their teeth exposed like crocodylians'  But, the issue keeps being debated and going back and forth - I do hope that someday there will be some degree of consensus about it, one way or the other. I'll follow where the science leads, of course.

It's just the way the skulls are formed that makes me doubt the "lips" hypothesis.But of course,new discoveries can always change my mind.Who knows what will be discovered tomorrow?

That reminds me of this Witton quote in general & the bolded part in particular:

Significantly, I can't find any tyrannosaurid skulls where these possible scale correlates extend right to the base of the maxilla (see photos, above). Rather, they terminate a few centimetres above the line of labial foramina, and this might have bearing on ongoing discussions about dinosaur lips. Scleroglossan lizards (the group that includes geckos, skinks, varanoids and amphisbaenians) frequently have osteoderms on their faces which cover their snouts (including the maxillae) except for a region around the labial foramina, which is smooth. This seems to relate to the presence of lip tissues displacing the scales from the skull and prohibiting formation of a epidermal correlate adjacent to the toothrow. Their maxillary juxtaposition of epidermal correlates is the same configuration that we see in tyrannosaurids as well as a number of other non-avian dinosaurs with maxillary epidermal correlates (e,g, pachycephalosaurids, ankylosaurids, some ceratopsids) and this has to be regarded consistent with hypotheses of extra-oral 'lips' in tyrannosaurids and other dinosaurs. If we add this to the evidence from foramina counts (Morhardt 2009, also see above) as well as other arguments for extra-oral tissues the case for crocodylian-like exposed teeth is looking increasingly doubtful. I must admit to thinking that proponents of exposed dinosaur teeth really need to start making better cases for this idea: most ways we can slice this particular debate suggests that extra-oral tissues are looking likely (and no, the common argument that their teeth were too big to be sheathed isn't valid: it's simply a speculation based on incredulity, not actual data from dinosaur skulls).

With respect to Mark Witton,I have already read the text,but I still agree more with Carr on that subject for now.And it's not simply because of incredulity or I "refuse to believe" as Witton says which shows his frustration at this idea not being as widely accepted as he would like it to be.

[Lanthanotus]

Said it before...

... 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 (porcines, 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).

Just for consideration.... skulls of Lanthanotus borneensis and Varanus panoptes, both closed to the max. Both species bear fully closed mouth to protect their teeth and inner mouth from environmental influences.


Besides the point of teeth being very delicate when constantly exposed to dryness and light (they get brittle and crack... a bad condition on a bone crusher as T. rex)is that lips add further benefits. The saliva within the mouth does not only supply a lubricant faciliating the teeth in penetrating skin and flesh of prey more easily, but also supplies a medium balancing the bacterial flora within the mouth, lowering the risk of  pathogenic germs attacking the body. These functions obviously can only work to a full extent when the mouth is fully closed and covered with lips.

[Reptilia]

I think that our misconception of lipless dinosaurs, or more specifically theropods, is still an heritage of those shrink-wrapped reconstructions that were popular in the 80s and 90s. In the modern animal kingdom exposed teeth are exceptions, so there's no logical reason to think that in the past things were the opposite, considering that theropods were a large portion of terrestrial fauna. Think of theropods as properly fleshed up animals and you'll see that exposed teeth looks out of place.

[stargatedalek]

Even fully aquatic animals will go to extreme lengths to keep their teeth covered whenever possible, to the point many fish with large teeth have channels for them to slot into.

[John]

This is an exception to what is generally seen rather than the norm,but the exposed upper tusks of Gomphotherium had a layer of enamel that was just fine.This is why I do not take seriously the claims that enamel covered teeth must have been completely enclosed in the mouth for moisture or it will crack away.And yes,theropods do look odd with exposed teeth,but even with them completely covered as they are in most animals,they still are very odd looking with nothing else quite like them.

[stargatedalek]

This is an exception to what is generally seen rather than the norm,but the exposed upper tusks of Gomphotherium had a layer of enamel that was just fine.This is why I do not take seriously the claims that enamel covered teeth must have been completely enclosed in the mouth for moisture or it will crack away.And yes,theropods do look odd with exposed teeth,but even with them completely covered as they are in most animals,they still are very odd looking with nothing else quite like them.

But was Gomphotherium actually using those teeth "as teeth"? Their position really makes them look like they're for display or combat but not for chewing food. They're also significantly larger and thicker than theropod teeth, and even if it was using them to eat they don't need to be as sharp let alone possess fine serrations on them like theropod teeth do.

One thing that rarely seems to get brought up is that meat eating animals need to be more careful about keeping their teeth clean, not just because of the kind of food but also because serrated teeth can get food caught in them more easily. Saliva is not only good for the teeth but it also helps to keep the gums clean and free of debris.

[John]

This is an exception to what is generally seen rather than the norm,but the exposed upper tusks of Gomphotherium had a layer of enamel that was just fine.This is why I do not take seriously the claims that enamel covered teeth must have been completely enclosed in the mouth for moisture or it will crack away.And yes,theropods do look odd with exposed teeth,but even with them completely covered as they are in most animals,they still are very odd looking with nothing else quite like them.

But was Gomphotherium actually using those teeth "as teeth"? Their position really makes them look like they're for display or combat but not for chewing food. They're also significantly larger and thicker than theropod teeth, and even if it was using them to eat they don't need to be as sharp let alone possess fine serrations on them like theropod teeth do.

One thing that rarely seems to get brought up is that meat eating animals need to be more careful about keeping their teeth clean, not just because of the kind of food but also because serrated teeth can get food caught in them more easily. Saliva is not only good for the teeth but it also helps to keep the gums clean and free of debris.

Gomphotherium had enamel covered upper tusks that had survived without constant moisture.That is fact.That makes the enamel needing to have been covered at all times or else it cracks idea flawed at best,regardless of whatever feeding habits carnivorous dinosaurs had.This is by no means a closed subject of course,but I still lean more towards Carr than Witton on the subject for now at least.

[WarrenJB]

I think Mark's taking a bit of a kicking in the shins here, perhaps partly for something he's not arguing for. This isn't his first article on the topic of lips and teeth, and he's acknowledged that the presence of enamel on tusks and large teeth, it's exposure to the external environment, and the aquatic or non-aquatic habits of their owners is a pretty mixed bag:

markwitton-com.blogspot.co.uk/2016/10/exposed-teeth-in-dinosaurs-sabre-tooths.html

The takehome message from that, in my opinion, is that enamel is not the be-all end-all of tooth exposure. The fallback position seems to be the default position too - that the vast majority of vertebrates, barring only some of those with unusually enlarged and specialised tusks/fangs, have enclosed teeth for some reason. That's before getting into Witton's nitty-gritty examination of osteological correlates in crocodylians and tyrannosaurids, and the terribly limited EPB. After all that, I'd say the burden of proof is on Carr to properly explain how tyrannosaurids go against the grain.
'Cos to bruise his shins a bit, I thought the deliberation about Daspletosaurus horneri's facial integument was too vague, before this current blog post. "Oh, it's got foramina. And that bumpy texture? Exactly like a crocodile."
Well, no. If Mark's frustrated by the reasoning approaching the level of a 'just-so' story ('How the Tyrannosaurus lost it's lips'), like sauropods snorkelling in swamps or swan-necked plesiosaurs, I can well understand the feeling.

[stargatedalek]

I don't think anyone's actually suggesting that enamel would split or crack if exposed to air for long periods, that simply isn't true. What happens is that teeth become weaker and more importantly here they become worn smooth.

This is why animals with exposed teeth, like elephants, pterosaurs, and crocodiles all have adaptations shared between them specifically to combat this, adaptations which theropods lack. All of these animals have extremely thick teeth to combat the comparative frailty, and their teeth are all conical with no serrations as those would be worn down to nothing very quickly. Pterosaur teeth in particular are so thick that they need to be spaced very generously to compensate.

In contrast theropod teeth are thin, tightly packed, and many have fairly extreme serration. Theropod teeth are so thin and frankly dainty that the only modern animals with teeth even vaguely similar are all fish, which can go to pretty extreme lengths to take care of their teeth despite being aquatic.

[John]

I don't think anyone's actually suggesting that enamel would split or crack if exposed to air for long periods, that simply isn't true. What happens is that teeth become weaker and more importantly here they become worn smooth.

This is why animals with exposed teeth, like elephants, pterosaurs, and crocodiles all have adaptations shared between them specifically to combat this, adaptations which theropods lack. All of these animals have extremely thick teeth to combat the comparative frailty, and their teeth are all conical with no serrations as those would be worn down to nothing very quickly. Pterosaur teeth in particular are so thick that they need to be spaced very generously to compensate.

In contrast theropod teeth are thin, tightly packed, and many have fairly extreme serration. Theropod teeth are so thin and frankly dainty that the only modern animals with teeth even vaguely similar are all fish, which can go to pretty extreme lengths to take care of their teeth despite being aquatic.

"Dainty" is not something that comes to mind when thinking of the banana sized teeth of adult Tyrannosaurus rex.But I do see what you mean in general.But theropod dinosaurs were constantly shedding teeth all their lives,so they wouldn't have much of a problem with any worn down enamel or anything like that.
Now here is something that will make your head explode:this whole enamel business neither proves nor disproves whether tyrannosaurids had exposed teeth or not.

[HD-man]

With respect to Mark Witton,I have already read the text,but I still agree more with Carr on that subject for now.And it's not simply because of incredulity or I "refuse to believe" as Witton says which shows his frustration at this idea not being as widely accepted as he would like it to be.

The point of me quoting Witton (which WarrenJB reiterated) was to remind "lipless" proponents the burden of proof is on them.

I think Mark's taking a bit of a kicking in the shins here, perhaps partly for something he's not arguing for. This isn't his first article on the topic of lips and teeth, and he's acknowledged that the presence of enamel on tusks and large teeth, it's exposure to the external environment, and the aquatic or non-aquatic habits of their owners is a pretty mixed bag:

markwitton-com.blogspot.co.uk/2016/10/exposed-teeth-in-dinosaurs-sabre-tooths.html

The takehome message from that, in my opinion, is that enamel is not the be-all end-all of tooth exposure. The fallback position seems to be the default position too - that the vast majority of vertebrates, barring only some of those with unusually enlarged and specialised tusks/fangs, have enclosed teeth for some reason. That's before getting into Witton's nitty-gritty examination of osteological correlates in crocodylians and tyrannosaurids, and the terribly limited EPB. After all that, I'd say the burden of proof is on Carr to properly explain how tyrannosaurids go against the grain.
'Cos to bruise his shins a bit, I thought the deliberation about Daspletosaurus horneri's facial integument was too vague, before this current blog post. "Oh, it's got foramina. And that bumpy texture? Exactly like a crocodile."
Well, no. If Mark's frustrated by the reasoning approaching the level of a 'just-so' story ('How the Tyrannosaurus lost it's lips'), like sauropods snorkelling in swamps or swan-necked plesiosaurs, I can well understand the feeling.

[John]

With respect to Mark Witton,I have already read the text,but I still agree more with Carr on that subject for now.And it's not simply because of incredulity or I "refuse to believe" as Witton says which shows his frustration at this idea not being as widely accepted as he would like it to be.

The point of me quoting Witton (which WarrenJB reiterated) was to remind "lipless" proponents the burden of proof is on them.

I think Mark's taking a bit of a kicking in the shins here, perhaps partly for something he's not arguing for. This isn't his first article on the topic of lips and teeth, and he's acknowledged that the presence of enamel on tusks and large teeth, it's exposure to the external environment, and the aquatic or non-aquatic habits of their owners is a pretty mixed bag:

markwitton-com.blogspot.co.uk/2016/10/exposed-teeth-in-dinosaurs-sabre-tooths.html

The takehome message from that, in my opinion, is that enamel is not the be-all end-all of tooth exposure. The fallback position seems to be the default position too - that the vast majority of vertebrates, barring only some of those with unusually enlarged and specialised tusks/fangs, have enclosed teeth for some reason. That's before getting into Witton's nitty-gritty examination of osteological correlates in crocodylians and tyrannosaurids, and the terribly limited EPB. After all that, I'd say the burden of proof is on Carr to properly explain how tyrannosaurids go against the grain.
'Cos to bruise his shins a bit, I thought the deliberation about Daspletosaurus horneri's facial integument was too vague, before this current blog post. "Oh, it's got foramina. And that bumpy texture? Exactly like a crocodile."
Well, no. If Mark's frustrated by the reasoning approaching the level of a 'just-so' story ('How the Tyrannosaurus lost it's lips'), like sauropods snorkelling in swamps or swan-necked plesiosaurs, I can well understand the feeling.

The statement "...to remind  "lipless" proponents the burden of proof on them." is simply untrue.So I'm going to have to disagree with you and WarrenJB on this one.Your arguments just seem to come more from a general dislike of Thomas Carr then anything else.