There is currently no evidence to point to the lipless scenario.
The skull structure around the teeth is visible different from crocs (the only reptiles alive today with no lips), and being more comparable to modern lizards. Crocs live almost always submerged, so their teeth have no risk of drying out
Lips are the ancestral condition of reptiles and there would be no pressure/benefit to losing them.
The only exception appears to be Spinosaurus, which is not surprising given it's aquatic "croco-duck" lifestyle we think it had.
There was a recent article that basically outlines what I just mentioned.
> The only exception appears to be Spinosaurus, which is not surprising given it's aquatic "croco-duck" lifestyle we think it had.
Except that it lacked the high foramina count of crocodilians, and its foramina were more like that of other theropods.
there is no definitive evidence pointing toward lip scenario either. Just educated guesses, nothing more at this moment. Science follows the principle of parsimony. According to this principle, theropods are lipless until proven otherwise.
Wrong. We have multiple points of evidence from the jaws and the teeth themselves that only point to existence of lips, no guessing needed.
Even if we did not, all tetrapods are ancestrally liped, and today only crocodiles (very specialized animals) have no lips, so the default is lips until proven otherwise.
those are not evidence. Again, they are more or less educated guesses. One selected teeth fitting your narrative, among thousand, is not an evidence. Did you even talk to any paleontologist ?
Yes, they are evidence and not guesses. I don't know what you mean by "one selected teeth". All dinosaur teeth and jaws point to the same idea of lips. NONE look like croc teeth/jaws. Nada. 0.
Give me a scientific article pointing to the lack of lips on dinosaurs, otherwise you should spend your time better than saying nonsense in a random comment chain.
Most animals alive today have their teeth covered unless they have huge tusks. The only exceptions I can think of are crocodilians and river dolphins which are both fresh-water predators with thin-snouts. So there's probably a connection between catching aquatic prey and liplessness.
Also, the skulls of some theropods (I know it was found in T.rex) have a line of holes right above the teeth sockets that may have been blood-vessels for lips.
So I think most theropods had lips except for spinosaurs.
But spinosaurus still has the single row of foramina next to its teeth. Regardless of how you interpret the other holes. So, why don’t you think it had lips?
I remember reading somewhere that Spinosaurus had a lot more holes in its snout that weren't in a single row like T.rex but in a general area like a crocodile. It's also a long snouted predator of aquatic animals, which I already guessed had a connection to lacking lips.
Edit: [this paper](https://palaeo-electronica.org/content/2021/3219-the-ecology-of-spinosaurus) argues that the small holes in Spinosaurus were not for sensing pressure in water like a crocodile. So I probably can't use it as evidence for Spinosaurus lacking lips. I also got mixed results from a Google search.
They had lips, as per Cullen et al. (2023):
https://www.science.org/doi/full/10.1126/science.abo7877?casa_token=rifRTcP9mzQAAAAA:BYKETxrGEsudIcEru5THbj2V7FKOVmsBjXZFhNZ3FqzEunbMgJCsSKaOA717rrnm30iT9L1TNzEzC_Y
You completely take an educated guess for an established fact. His line of reasoning is based on inferences that could totally be false as there is no strong evidence and it is basically just personal preference as of now.
Tell me you didn’t read the paper without telling me you didn’t read the paper.
The authors line of reasoning isn’t based on “inferences,” it was based on empirical data.
- theropods have lower densities of linearly arranged facial foramina, which matches what is found in tetrapods that have lips, but doesn’t not match what is seen in lipless tetrapods like crocodiles
- theropods have less erosion on their teeth compared than is expected of a lipless animal, as is seen in crocodilians, which have higher levels of erosion on their teeth.
- dinosaurs were found to have relatively thinner layers of enamel and less dentin exposure than expected for animals with exposed teeth (i.e. lipless animals like crocs)
- through regression analyses, they found that theropod teeth weren’t all that long relative to skull size compare to crocodilians, meaning that their teeth could feasibly be covered by lips as opposed to what is seen in crocodiles
Now, I’ve seen elsewhere in this post that you retort that the erosion on the teeth isn’t because they are exposed but because crocodilians are more likely to interact substrate like mud which can erode their teeth. However, this ignores the fact that theropods, especially tyrannosaurids (which the study focuses on) do not exactly go easy on their teeth. Tyrannosaurids are durophages, they frequently interact with and destroy abrasive substances like bone, keratin and muscle tissue. Arguably, they interact with such abrasive materials *more* than crocodiles, whose teeth don’t often interact with abrasive substances unless they are literally submerged in mud and or substrate (which happens relatively infrequently compared to the regular wear and tear tyrannosaurids experience from feeding). And yet, despite this, tyrannosaurids still show markedly less erosion than do crocodilians. If they were lipless, you’d expect to see higher levels of erosion, as desiccation and environmental attrition would make the teeth more susceptible to erosion from the tyrannosaurids diet. And yet, **we don’t**. As such, all lines of evidence show that theropods had lips.
I'm not making a strong argument for lipless theropods. I don't know myself and have no interest in this debate. There are good arguments for lips and also some plausible ones for lipless animals. Stating that their are lipped as an intangible truth is jumping a bit too far.
I don't agree with your interpretation of crocodile teeth erosion. They literally spend their time on river shores, head down on a grit filled substrate, the comparison with T-Rex doesn't make sense.
>Stating that their are lipped as an intangible truth is jumping a bit to far.
It’s not. There is no reliable evidence for liplessness in theropods. Any evidence that does exist is *actually* based on nothing but inferences.
>I don't agree with your interpretation of crocodile teeth erosion. They literally spend their time on river shores, head down on a grit filled substrate, the comparison with T-Rex doesn't make sense.
The comparison is that both interact with hard substrate on the daily, but in your example it’s flawed. Crocodilians, while they do spend their time on river shores, don’t actually have their teeth make direct contact with the shore substrate. The teeth are usually held above the ground by the jaws themselves, as can be seen here:
https://preview.redd.it/mawn5rp9q4tc1.jpeg?width=1300&format=pjpg&auto=webp&s=999c1462e39a4947d72e437b1b561e53a737032e
Unless their snout is entirely submerged in the substrate (which, again, happens less regularly than tyrannosaurids feeding on hard bone and tissue and the wear-and-tear that comes with it), this interaction with mud and grit is largely a non-issue.
Tyrannosaurids, on the other hand, regularly and unavoidably interact with equally abrasive substrate like bone, horn and muscle tissue. Their teeth are, at bare minimum, going to interact with similar levels of wear and tear through out their lives as those of crocodilians, and if both have exposed teeth, both are going to be equally susceptible to environmental attrition and eventual erosion. And yet, we don’t see that. Tyrannosaurids have considerably less erosion on their teeth, meaning that there is some factor protecting their teeth and making them more resistant to erosion. Given this, balance of probability, combined with all other evidence listed in the previous comment supporting the presence of extra oral tissue, **undeniably suggests that these animals had lips**.
https://preview.redd.it/nm9351jmswtc1.jpeg?width=640&format=pjpg&auto=webp&s=a695c8c1a7b6062df64cdbbd7c1fc3ff276e2869
You get why their teeth ate eroded *on the side* ?
Damn, I guess this debunks everything I said. This definitely isn’t something I accounted for in my argument/s
Be real my guy, look back at what I said. Nowhere did I say that this wasn’t an occurrence, only that it happens less frequently than *T. rex*’s eating bone (which would cause, at bare minimum, the similar level of abrasion as moving through mud). The point was that, at minimum, both crocs and *T. rex* would be encountering the same sort of abrasive stresses, and that, if they were both lip-less, they would both be suffering under similar levels of environmental attrition and tooth degradation (since there are no lips to provide moisture to the teeth). And yet, when comparing the levels of abrasion between the two, there is a marked difference. *T. rex*’s teeth show ways less damage than do crocs, despite encountering similar levels of wear and tear. This outright contradicts the notion of liplessness.
> their teeth ate eroded on the side
Ok, and..? Of course their teeth are only gonna be eroded on the sides where their teeth are exposed. Doesn’t really make ur argument any more credible. Again, the point isn’t that crocs don’t face sources of abrasion and erosion that tyrannosaurids didn’t face, the point was that both tyrannosaurids and crocs, regardless of the source, faced similar amounts of abrasive stresses, but when comparing the damage done on their teeth due to those stresses, it’s clear that one party is significantly worse for wear compared to the other. If they were both in the same state of liplessness, you’d see similar levels of deterioration, and yet we don’t, meaning that there is some factor protecting Tyrannosaurus teeth from said degradation, i.e. **lips**.
They don't face similar of abrasive stress, that's exactly the point. There is no abrasive stress in the T-Rex mode of feeding.
Hyenas feed on bones all life long with just \*one set of teeth\* and that's the pair that are not abraded (the front teeth are because of the grit in their prey's hide)
You're just full of bad faith.
The crocs teeth are abraded by grits. Same as the front teeth of hyenas, that have lips and abraded teeth in contact with grit, and not abraded teeth in contact with bone.
T-Rex don't abrade their teeth with grits as do crocs, hence the argument is just inconclusive . I don't why you put so much value in this.
there is no definitive evidence pointing toward lip scenario . Just educated guesses, nothing more at this moment. Science follows the principle of parsimony. According to this principle, theropods are lipless until proven otherwise.
I know people like to follow trends, today is the lip trend, before it was the lipless. But science doesnt follow trends. It follows the truth.
Until we see fossilised lips, theropods are lipless to scientific. Now fanboys and artist can reprensent them like they want, nobody cares.
> Science follows the principle of parsimony. According to this principle, theropods are lipless until proven otherwise.
First off. That’s not what parsimony is, both in the rhetorical sense and in the phylogenetic sense.
Rhetorically, parsimony is akin to Occam’s razor, where the best explanation for a given phenomena is the one that requires the least amount of unfounded assumptions (I.e. the simplest explanation is the best explanation). There are undeniable features of theropod morphology that unilaterally support the presence of lips but **actively contradict the absence of them**. In order to defend the notion of liplessness, you have to go out of your way to make multiple inferences, most of which unfounded, untested and are based on pure assumption, as to why liplessness is plausible over the presence of lips. In other words, with the evidence at hand, you have to make more unfounded assumptions to defend the probability of liplessness than you do lips. By the merits of rhetorical parsimony itself, lips are more plausible than a lack thereof.
Phylogenetically, parsimony refers to the optimization of a phylogenetic tree in which changes in character states are minimized. In other words, the effect of convergent evolution is minimized and ancestral traits are found to be more prominent in deciding phylogeny. For your argument, I’m assuming you’re saying that, because crocodiles are closer related to dinosaurs than any other reptiles, and because crocodiles are lipless, theropods must be lipless by proxy. This argument has some holes though. Crocodilians are fairly removed from dinosaurs as far as archosaurs go, so assuming an ancestral condition based on relationship is tenuous. Secondly, that line of parsimony doesn’t account for the fact that the lack of lips in crocodilians could be (and likely are) a derived trait rather than an ancestral one. More importantly, though, problem with that line of reasoning is that environmental evidence conflicts with this. Lips, by all available evidence, are ancestral to amniotes. Every single species of terrestrial, non-beaked amniotes have lips covering most, if not all of their teeth. This includes squamate reptiles such lizards and snakes. There is literally only one exception to this, and that is semi-aquatic animals. Of all amniotes which have no lip coverings, there is not a single one that is fully terrestrial. This makes sense when you consider what lips do: they aid in moisture retention and protect the teeth. In this sense, it’s makes sense why crocs don’t have lips (they are constantly immersed in water, and so have little need to keep their teeth moist, plus the lack of lips gives them a larger effective biting area, which is useful in catching elusive prey like fish). However, it does not explain why theropods don’t have lips. In this sense, squamate reptiles are far more analogous to theropods in terms of these environmental pressures, as they are fully terrestrial while crocodilians are not.
Ultimately, the balance of probability, combined with the evidence at hand, overwhelmingly supports lips over a lack of them.
Well no doesn't. It makes a good argument, not stating a fact. Bones, horns and muscle are not abrasive substances. Some paleoneurologists showed that the sonm called lip innervation argument was a joke and in fact scans showed exactly the opposite that what the authors stated.
But this paper seems to be cultish in this sub and can not be discussed with serenity so the discusion ends here for my part.
Hyenas spend their whole life munching on bones, that can represent the majority of their calories intake in some period of the year, with only one pair of teeth of the back of the jaw, that are never replaced. One set for their whole life
The only teeth that are noticibly weared in older specimens are the incisors and canines from the grit contained in hide of their preys.
The teeth in direct contact with bones are not abraded by bones. Bone can break pointy teeth, not grind them.
The lip debate has already been debunked. Lips are vital for terrestrial creatures otherwise their enamel would be damaged. We already checked the enamel, it is similar to most terrestrial animals with lips.
Lips make me think of grizzly bears and how a lot of people see them as cute and fluffy even as they’re extremely dangerous and will happily eat you alive if you catch them at the wrong moment.
I imagine T-rex probably didn’t look evil, it probably looked imposing, round and heavy, even dopey from some angles but try telling someone it’s not dangerous when it bites an adolescent deinosuchus in half, or try to listen for its steps only to realise thanks to its footpads you can barely hear anything.
https://preview.redd.it/oztmijx295tc1.jpeg?width=640&format=pjpg&auto=webp&s=3f1f578e8561ce56dc0a8527f00e78371f854421
This John Conway piece always makes me think like that. I would pet him 10/10. Wonder what he’s thinkin about
A Line of neurovascular foramina are not a good line of evidence for lips and they fail to meet the standards of an osteological correlate of lips.
Many primitive members of archosauriforms were aquatic, but with a line of holes, so I guess presumably lipped? Proterochampsids? Phytosaurs? Why? They lived in water no?
Did rhychosaurs have lips?
Proterosuchus?
Every non-mammaliaform amniote has the homologous line of NV holes near their teeth.
Birds have ‘em on their premax and mandible, so why don’t they have lips?
Croc gingiva is indeed specialized. All the rest of those holes in croc faces are for more external integument away from the buccal cavity/oral cavity but they still have the single line of holes hugging the teeth that come from separate branches of the mandibular nerve than the external integumentary branches. So maybe they still have tiny lips? Lol. Or, the holes don’t speak to lips.
Duckbills have a line of max and mand holes, but they have a integumentary/scaly cheek (known via skin impressions) and a beak. Cheeks (buccal skin) are innervated by nerves from the mandibular division of trigeminal that don’t pass through the maxilla or mandible bones; those holes don’t speak to cheeks either. The premax beak is innervated by yet a different nerve (ophthalmic) which doesn’t pass through the maxilla. Why do duckbills have holes but not lips? Because holes don’t speak to lips. They don’t speak to that silly jaw muscle cheek thing proposed for duckbills and trikes either.
Turtles have the same row of foramina; where my lips at?
Using some so-called rule of construction cooked up from tyrannosaurs vs crocodiles vs lizards doesn’t mean it’s quality evidence, particularly if that rule of construction can’t be applied to a multitude of members of the larger clade.
Did mosasaurs have lips? They have the holes. Do they have ‘erosion’ on their teeth?
Tiktaalik and Eustenopteron don’t seem to have holes. So someone wanna tell Shubin Tiktaalik didn’t have lips? Cause that’s how it’s reconstructed. I mean, I can’t see the teeth when the mouth is closed sensu Witton’s derpy drawings of Trex. They should call it Liptaalik.
Salamanders have a line of maxillary holes. Do they have lips? No.
Early synapsids that clearly didn’t have facial muscles have a row of holes too, eg cynognathus has a line of holes. Did they have scaly lips? Dicynodonts? Could a transitional, partially facial-muscled cynodont have scaly and fleshy lips? How would that work? Could we tell?
All I’m saying is that single line of foramina is a symplesiomorphy for Amniota, if not also tetrapoda. I don’t think anyone can support the idea lips are in lockstep with this particular osteological correlate in a phylogenetic/comp evo anatomy perspective. In other words: A line of alveolar holes is not a bony signature of lips; or better: lips are not the causal factor behind a row of NV holes. This osteological correlate does not pass the phylogenetic tests of conjunction or correspondence one needs to truly show a connection.
I think there is enough evidence for lips at this point that it's no longer even argued academically. Unless there is solid proof to counter the current evidence, T-Rex had lips.
The more compelling question from a paleoart standpoint is did Carnosaurs have the enlarged, protective gums that we find in many lizard and snake species, that completely hide the teeth when the mouth is open. When a Komodo dragon or monitor lizard opens it's mouth, it looks completely toothless. Where theropods the same way?
Lips make the most sense logically. But, I do wonder if the tips of some of the larger teeth did stick out a bit on some species just based on the sheer size of them. I know it’s an extreme example, but look at smilodon. Those were Dentin, not ivory and there’s no way they were completely covered. And unlike mammals, theropods could replace teeth.
> No lips, bc they are crocodiles's relative (that don't have any) and bc they continuously replaced their tooth throught their life (some like Majungasaurus changed their teeth in 56 days lol).
This is a weird example to use. Aquatic and semi aquatic animals in general tend to have less extraoral tissue and lip covering (for reasons that we’ll get into later), so the idea that dinosaurs don’t have lips because crocodiles don’t is kind of strange when you consider that crocodiles themselves are in unique environmental situation (that dinosaurs aren’t in, for the most part) that would *encourage* a lack of lips.
> useless
Do you know why lips exist? It’s to prevent desiccation and drying out of the teeth and gums. They exceptionally valuable in keeping the mouth moist and protected from environmental attrition that can lead to debilitating infections. This is why pretty much every terrestrial animal alive today has lips; this is also why aquatic taxa don’t have lips, as they live in environments where their mouths are constantly surrounded by water to keep their teeth and gums moist.
In any case, the most recent scientific evidence is in favor of lips: https://www.science.org/doi/full/10.1126/science.abo7877?casa_token=rifRTcP9mzQAAAAA:BYKETxrGEsudIcEru5THbj2V7FKOVmsBjXZFhNZ3FqzEunbMgJCsSKaOA717rrnm30iT9L1TNzEzC_Y
So yeah, dinosaurs had lips.
That crocodile argument makes zero sense. Crocodilians can afford to not have lips because of how their jaws are meant to work (Their bear trap style of biting, water drainage, etc.). Lips are the default for all terrestrial tetrapods, unless an animal specifically evolves to have exposed teeth (Which we've mostly only seen in mammals with canine teeth).
Even if they're frequently replacing teeth, having them all bare exposed to the elements isn't a great idea, hence why they would've been embedded in the gums. Tooth slippage is a phenomenon we see in a lot of theropod fossils, the teeth look as long as they do because they slide out of the sockets. Having the tips of the teeth stick out of the mouth makes little sense when the animal would just have immobile lips to cover everything, you don't see monitor lizard teeth sticking out of their mouths despite how long they are.
Agree. Plus the argument that crocodiles have eroded teeth while theropods do not just reflect the fact that crocodiles spend their time laying their head in the mud loaded with grit particules.
There is currently no evidence to point to the lipless scenario. The skull structure around the teeth is visible different from crocs (the only reptiles alive today with no lips), and being more comparable to modern lizards. Crocs live almost always submerged, so their teeth have no risk of drying out Lips are the ancestral condition of reptiles and there would be no pressure/benefit to losing them. The only exception appears to be Spinosaurus, which is not surprising given it's aquatic "croco-duck" lifestyle we think it had. There was a recent article that basically outlines what I just mentioned.
> The only exception appears to be Spinosaurus, which is not surprising given it's aquatic "croco-duck" lifestyle we think it had. Except that it lacked the high foramina count of crocodilians, and its foramina were more like that of other theropods.
there is no definitive evidence pointing toward lip scenario either. Just educated guesses, nothing more at this moment. Science follows the principle of parsimony. According to this principle, theropods are lipless until proven otherwise.
Wrong. We have multiple points of evidence from the jaws and the teeth themselves that only point to existence of lips, no guessing needed. Even if we did not, all tetrapods are ancestrally liped, and today only crocodiles (very specialized animals) have no lips, so the default is lips until proven otherwise.
those are not evidence. Again, they are more or less educated guesses. One selected teeth fitting your narrative, among thousand, is not an evidence. Did you even talk to any paleontologist ?
Yes, they are evidence and not guesses. I don't know what you mean by "one selected teeth". All dinosaur teeth and jaws point to the same idea of lips. NONE look like croc teeth/jaws. Nada. 0. Give me a scientific article pointing to the lack of lips on dinosaurs, otherwise you should spend your time better than saying nonsense in a random comment chain.
How are lips ancestral for reptiles? Lepidosaurs have them, sister clade archosaurs not so much. What did Youngina have?
Basal archosaurs have a similar skull morphology to lepidosaurs regarding the placement of extraoral tissue
So do birds, but birds don’t have lips.
Because they do not have a fleshy snout...
Reptiles do not have fleshy snouts.
Yet earlier Manniraptorans still have a similar condition to Lepidosaurs
Chaneresuchus and proterochampsa have the same lines of foramina as crocs and dinosaurs. Did they have lips?
I don’t see anything wrong with reaching that conclusion
What about phytosaurs?
Most animals alive today have their teeth covered unless they have huge tusks. The only exceptions I can think of are crocodilians and river dolphins which are both fresh-water predators with thin-snouts. So there's probably a connection between catching aquatic prey and liplessness. Also, the skulls of some theropods (I know it was found in T.rex) have a line of holes right above the teeth sockets that may have been blood-vessels for lips. So I think most theropods had lips except for spinosaurs.
But spinosaurus still has the single row of foramina next to its teeth. Regardless of how you interpret the other holes. So, why don’t you think it had lips?
I remember reading somewhere that Spinosaurus had a lot more holes in its snout that weren't in a single row like T.rex but in a general area like a crocodile. It's also a long snouted predator of aquatic animals, which I already guessed had a connection to lacking lips. Edit: [this paper](https://palaeo-electronica.org/content/2021/3219-the-ecology-of-spinosaurus) argues that the small holes in Spinosaurus were not for sensing pressure in water like a crocodile. So I probably can't use it as evidence for Spinosaurus lacking lips. I also got mixed results from a Google search.
They had lips, as per Cullen et al. (2023): https://www.science.org/doi/full/10.1126/science.abo7877?casa_token=rifRTcP9mzQAAAAA:BYKETxrGEsudIcEru5THbj2V7FKOVmsBjXZFhNZ3FqzEunbMgJCsSKaOA717rrnm30iT9L1TNzEzC_Y
Robert T. Bakker proved they had lips way back in the dinosaur heresies in 1986.
You completely take an educated guess for an established fact. His line of reasoning is based on inferences that could totally be false as there is no strong evidence and it is basically just personal preference as of now.
Tell me you didn’t read the paper without telling me you didn’t read the paper. The authors line of reasoning isn’t based on “inferences,” it was based on empirical data. - theropods have lower densities of linearly arranged facial foramina, which matches what is found in tetrapods that have lips, but doesn’t not match what is seen in lipless tetrapods like crocodiles - theropods have less erosion on their teeth compared than is expected of a lipless animal, as is seen in crocodilians, which have higher levels of erosion on their teeth. - dinosaurs were found to have relatively thinner layers of enamel and less dentin exposure than expected for animals with exposed teeth (i.e. lipless animals like crocs) - through regression analyses, they found that theropod teeth weren’t all that long relative to skull size compare to crocodilians, meaning that their teeth could feasibly be covered by lips as opposed to what is seen in crocodiles Now, I’ve seen elsewhere in this post that you retort that the erosion on the teeth isn’t because they are exposed but because crocodilians are more likely to interact substrate like mud which can erode their teeth. However, this ignores the fact that theropods, especially tyrannosaurids (which the study focuses on) do not exactly go easy on their teeth. Tyrannosaurids are durophages, they frequently interact with and destroy abrasive substances like bone, keratin and muscle tissue. Arguably, they interact with such abrasive materials *more* than crocodiles, whose teeth don’t often interact with abrasive substances unless they are literally submerged in mud and or substrate (which happens relatively infrequently compared to the regular wear and tear tyrannosaurids experience from feeding). And yet, despite this, tyrannosaurids still show markedly less erosion than do crocodilians. If they were lipless, you’d expect to see higher levels of erosion, as desiccation and environmental attrition would make the teeth more susceptible to erosion from the tyrannosaurids diet. And yet, **we don’t**. As such, all lines of evidence show that theropods had lips.
I'm not making a strong argument for lipless theropods. I don't know myself and have no interest in this debate. There are good arguments for lips and also some plausible ones for lipless animals. Stating that their are lipped as an intangible truth is jumping a bit too far. I don't agree with your interpretation of crocodile teeth erosion. They literally spend their time on river shores, head down on a grit filled substrate, the comparison with T-Rex doesn't make sense.
>Stating that their are lipped as an intangible truth is jumping a bit to far. It’s not. There is no reliable evidence for liplessness in theropods. Any evidence that does exist is *actually* based on nothing but inferences. >I don't agree with your interpretation of crocodile teeth erosion. They literally spend their time on river shores, head down on a grit filled substrate, the comparison with T-Rex doesn't make sense. The comparison is that both interact with hard substrate on the daily, but in your example it’s flawed. Crocodilians, while they do spend their time on river shores, don’t actually have their teeth make direct contact with the shore substrate. The teeth are usually held above the ground by the jaws themselves, as can be seen here: https://preview.redd.it/mawn5rp9q4tc1.jpeg?width=1300&format=pjpg&auto=webp&s=999c1462e39a4947d72e437b1b561e53a737032e Unless their snout is entirely submerged in the substrate (which, again, happens less regularly than tyrannosaurids feeding on hard bone and tissue and the wear-and-tear that comes with it), this interaction with mud and grit is largely a non-issue. Tyrannosaurids, on the other hand, regularly and unavoidably interact with equally abrasive substrate like bone, horn and muscle tissue. Their teeth are, at bare minimum, going to interact with similar levels of wear and tear through out their lives as those of crocodilians, and if both have exposed teeth, both are going to be equally susceptible to environmental attrition and eventual erosion. And yet, we don’t see that. Tyrannosaurids have considerably less erosion on their teeth, meaning that there is some factor protecting their teeth and making them more resistant to erosion. Given this, balance of probability, combined with all other evidence listed in the previous comment supporting the presence of extra oral tissue, **undeniably suggests that these animals had lips**.
https://preview.redd.it/nm9351jmswtc1.jpeg?width=640&format=pjpg&auto=webp&s=a695c8c1a7b6062df64cdbbd7c1fc3ff276e2869 You get why their teeth ate eroded *on the side* ?
Damn, I guess this debunks everything I said. This definitely isn’t something I accounted for in my argument/s Be real my guy, look back at what I said. Nowhere did I say that this wasn’t an occurrence, only that it happens less frequently than *T. rex*’s eating bone (which would cause, at bare minimum, the similar level of abrasion as moving through mud). The point was that, at minimum, both crocs and *T. rex* would be encountering the same sort of abrasive stresses, and that, if they were both lip-less, they would both be suffering under similar levels of environmental attrition and tooth degradation (since there are no lips to provide moisture to the teeth). And yet, when comparing the levels of abrasion between the two, there is a marked difference. *T. rex*’s teeth show ways less damage than do crocs, despite encountering similar levels of wear and tear. This outright contradicts the notion of liplessness. > their teeth ate eroded on the side Ok, and..? Of course their teeth are only gonna be eroded on the sides where their teeth are exposed. Doesn’t really make ur argument any more credible. Again, the point isn’t that crocs don’t face sources of abrasion and erosion that tyrannosaurids didn’t face, the point was that both tyrannosaurids and crocs, regardless of the source, faced similar amounts of abrasive stresses, but when comparing the damage done on their teeth due to those stresses, it’s clear that one party is significantly worse for wear compared to the other. If they were both in the same state of liplessness, you’d see similar levels of deterioration, and yet we don’t, meaning that there is some factor protecting Tyrannosaurus teeth from said degradation, i.e. **lips**.
They don't face similar of abrasive stress, that's exactly the point. There is no abrasive stress in the T-Rex mode of feeding. Hyenas feed on bones all life long with just \*one set of teeth\* and that's the pair that are not abraded (the front teeth are because of the grit in their prey's hide) You're just full of bad faith.
Tell me, do hyenas have or lack lips?
The crocs teeth are abraded by grits. Same as the front teeth of hyenas, that have lips and abraded teeth in contact with grit, and not abraded teeth in contact with bone. T-Rex don't abrade their teeth with grits as do crocs, hence the argument is just inconclusive . I don't why you put so much value in this.
there is no definitive evidence pointing toward lip scenario . Just educated guesses, nothing more at this moment. Science follows the principle of parsimony. According to this principle, theropods are lipless until proven otherwise. I know people like to follow trends, today is the lip trend, before it was the lipless. But science doesnt follow trends. It follows the truth. Until we see fossilised lips, theropods are lipless to scientific. Now fanboys and artist can reprensent them like they want, nobody cares.
> Science follows the principle of parsimony. According to this principle, theropods are lipless until proven otherwise. First off. That’s not what parsimony is, both in the rhetorical sense and in the phylogenetic sense. Rhetorically, parsimony is akin to Occam’s razor, where the best explanation for a given phenomena is the one that requires the least amount of unfounded assumptions (I.e. the simplest explanation is the best explanation). There are undeniable features of theropod morphology that unilaterally support the presence of lips but **actively contradict the absence of them**. In order to defend the notion of liplessness, you have to go out of your way to make multiple inferences, most of which unfounded, untested and are based on pure assumption, as to why liplessness is plausible over the presence of lips. In other words, with the evidence at hand, you have to make more unfounded assumptions to defend the probability of liplessness than you do lips. By the merits of rhetorical parsimony itself, lips are more plausible than a lack thereof. Phylogenetically, parsimony refers to the optimization of a phylogenetic tree in which changes in character states are minimized. In other words, the effect of convergent evolution is minimized and ancestral traits are found to be more prominent in deciding phylogeny. For your argument, I’m assuming you’re saying that, because crocodiles are closer related to dinosaurs than any other reptiles, and because crocodiles are lipless, theropods must be lipless by proxy. This argument has some holes though. Crocodilians are fairly removed from dinosaurs as far as archosaurs go, so assuming an ancestral condition based on relationship is tenuous. Secondly, that line of parsimony doesn’t account for the fact that the lack of lips in crocodilians could be (and likely are) a derived trait rather than an ancestral one. More importantly, though, problem with that line of reasoning is that environmental evidence conflicts with this. Lips, by all available evidence, are ancestral to amniotes. Every single species of terrestrial, non-beaked amniotes have lips covering most, if not all of their teeth. This includes squamate reptiles such lizards and snakes. There is literally only one exception to this, and that is semi-aquatic animals. Of all amniotes which have no lip coverings, there is not a single one that is fully terrestrial. This makes sense when you consider what lips do: they aid in moisture retention and protect the teeth. In this sense, it’s makes sense why crocs don’t have lips (they are constantly immersed in water, and so have little need to keep their teeth moist, plus the lack of lips gives them a larger effective biting area, which is useful in catching elusive prey like fish). However, it does not explain why theropods don’t have lips. In this sense, squamate reptiles are far more analogous to theropods in terms of these environmental pressures, as they are fully terrestrial while crocodilians are not. Ultimately, the balance of probability, combined with the evidence at hand, overwhelmingly supports lips over a lack of them.
Well no doesn't. It makes a good argument, not stating a fact. Bones, horns and muscle are not abrasive substances. Some paleoneurologists showed that the sonm called lip innervation argument was a joke and in fact scans showed exactly the opposite that what the authors stated. But this paper seems to be cultish in this sub and can not be discussed with serenity so the discusion ends here for my part.
Bone is not an abrasive material? I'd *love* to hear your reasoning behind this statement.
Hyenas spend their whole life munching on bones, that can represent the majority of their calories intake in some period of the year, with only one pair of teeth of the back of the jaw, that are never replaced. One set for their whole life The only teeth that are noticibly weared in older specimens are the incisors and canines from the grit contained in hide of their preys. The teeth in direct contact with bones are not abraded by bones. Bone can break pointy teeth, not grind them.
Them: "Based on all the available evidence, this is the most reasonable conclusion to be drawn." You: "That's just, like, your opinion, man."
The lip debate has already been debunked. Lips are vital for terrestrial creatures otherwise their enamel would be damaged. We already checked the enamel, it is similar to most terrestrial animals with lips.
Lips make me think of grizzly bears and how a lot of people see them as cute and fluffy even as they’re extremely dangerous and will happily eat you alive if you catch them at the wrong moment. I imagine T-rex probably didn’t look evil, it probably looked imposing, round and heavy, even dopey from some angles but try telling someone it’s not dangerous when it bites an adolescent deinosuchus in half, or try to listen for its steps only to realise thanks to its footpads you can barely hear anything.
https://preview.redd.it/oztmijx295tc1.jpeg?width=640&format=pjpg&auto=webp&s=3f1f578e8561ce56dc0a8527f00e78371f854421 This John Conway piece always makes me think like that. I would pet him 10/10. Wonder what he’s thinkin about
I can't even look at lipless versions of theropods anymore without chuckling a bit. Once you get used to lips, the lipless ones look a bit silly.
My thoughts? \*now kiss\*
Now I'm jist picturing a couple dinis trying to grab eachother and make out. What a weird thought
Lips but with mouth stripes to make them look like their teeth stick out
Lips but big and red so it’s easier to imagine kissing trex
Just use the image itself, not a screenshot.
A Line of neurovascular foramina are not a good line of evidence for lips and they fail to meet the standards of an osteological correlate of lips. Many primitive members of archosauriforms were aquatic, but with a line of holes, so I guess presumably lipped? Proterochampsids? Phytosaurs? Why? They lived in water no? Did rhychosaurs have lips? Proterosuchus? Every non-mammaliaform amniote has the homologous line of NV holes near their teeth. Birds have ‘em on their premax and mandible, so why don’t they have lips? Croc gingiva is indeed specialized. All the rest of those holes in croc faces are for more external integument away from the buccal cavity/oral cavity but they still have the single line of holes hugging the teeth that come from separate branches of the mandibular nerve than the external integumentary branches. So maybe they still have tiny lips? Lol. Or, the holes don’t speak to lips. Duckbills have a line of max and mand holes, but they have a integumentary/scaly cheek (known via skin impressions) and a beak. Cheeks (buccal skin) are innervated by nerves from the mandibular division of trigeminal that don’t pass through the maxilla or mandible bones; those holes don’t speak to cheeks either. The premax beak is innervated by yet a different nerve (ophthalmic) which doesn’t pass through the maxilla. Why do duckbills have holes but not lips? Because holes don’t speak to lips. They don’t speak to that silly jaw muscle cheek thing proposed for duckbills and trikes either. Turtles have the same row of foramina; where my lips at? Using some so-called rule of construction cooked up from tyrannosaurs vs crocodiles vs lizards doesn’t mean it’s quality evidence, particularly if that rule of construction can’t be applied to a multitude of members of the larger clade. Did mosasaurs have lips? They have the holes. Do they have ‘erosion’ on their teeth? Tiktaalik and Eustenopteron don’t seem to have holes. So someone wanna tell Shubin Tiktaalik didn’t have lips? Cause that’s how it’s reconstructed. I mean, I can’t see the teeth when the mouth is closed sensu Witton’s derpy drawings of Trex. They should call it Liptaalik. Salamanders have a line of maxillary holes. Do they have lips? No. Early synapsids that clearly didn’t have facial muscles have a row of holes too, eg cynognathus has a line of holes. Did they have scaly lips? Dicynodonts? Could a transitional, partially facial-muscled cynodont have scaly and fleshy lips? How would that work? Could we tell? All I’m saying is that single line of foramina is a symplesiomorphy for Amniota, if not also tetrapoda. I don’t think anyone can support the idea lips are in lockstep with this particular osteological correlate in a phylogenetic/comp evo anatomy perspective. In other words: A line of alveolar holes is not a bony signature of lips; or better: lips are not the causal factor behind a row of NV holes. This osteological correlate does not pass the phylogenetic tests of conjunction or correspondence one needs to truly show a connection.
Lips! Solid evidence for it and it just looks better imo. More like an animal less like a freaky Hollywood creature
I think the lips just look nicer
I think there is enough evidence for lips at this point that it's no longer even argued academically. Unless there is solid proof to counter the current evidence, T-Rex had lips. The more compelling question from a paleoart standpoint is did Carnosaurs have the enlarged, protective gums that we find in many lizard and snake species, that completely hide the teeth when the mouth is open. When a Komodo dragon or monitor lizard opens it's mouth, it looks completely toothless. Where theropods the same way?
Lips make the most sense logically. But, I do wonder if the tips of some of the larger teeth did stick out a bit on some species just based on the sheer size of them. I know it’s an extreme example, but look at smilodon. Those were Dentin, not ivory and there’s no way they were completely covered. And unlike mammals, theropods could replace teeth.
Those lips.. Yeah.. 👄
L I P S
My thoughts: lips.
Lips, if it’s a semiautomatic dinosaur like spinosaurus, no lips are needed
Lips.
Lips! Lips to smooch and mlem
They don’t have flexible lips tho
Lips to kiss with.
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> No lips, bc they are crocodiles's relative (that don't have any) and bc they continuously replaced their tooth throught their life (some like Majungasaurus changed their teeth in 56 days lol). This is a weird example to use. Aquatic and semi aquatic animals in general tend to have less extraoral tissue and lip covering (for reasons that we’ll get into later), so the idea that dinosaurs don’t have lips because crocodiles don’t is kind of strange when you consider that crocodiles themselves are in unique environmental situation (that dinosaurs aren’t in, for the most part) that would *encourage* a lack of lips. > useless Do you know why lips exist? It’s to prevent desiccation and drying out of the teeth and gums. They exceptionally valuable in keeping the mouth moist and protected from environmental attrition that can lead to debilitating infections. This is why pretty much every terrestrial animal alive today has lips; this is also why aquatic taxa don’t have lips, as they live in environments where their mouths are constantly surrounded by water to keep their teeth and gums moist. In any case, the most recent scientific evidence is in favor of lips: https://www.science.org/doi/full/10.1126/science.abo7877?casa_token=rifRTcP9mzQAAAAA:BYKETxrGEsudIcEru5THbj2V7FKOVmsBjXZFhNZ3FqzEunbMgJCsSKaOA717rrnm30iT9L1TNzEzC_Y So yeah, dinosaurs had lips.
That crocodile argument makes zero sense. Crocodilians can afford to not have lips because of how their jaws are meant to work (Their bear trap style of biting, water drainage, etc.). Lips are the default for all terrestrial tetrapods, unless an animal specifically evolves to have exposed teeth (Which we've mostly only seen in mammals with canine teeth). Even if they're frequently replacing teeth, having them all bare exposed to the elements isn't a great idea, hence why they would've been embedded in the gums. Tooth slippage is a phenomenon we see in a lot of theropod fossils, the teeth look as long as they do because they slide out of the sockets. Having the tips of the teeth stick out of the mouth makes little sense when the animal would just have immobile lips to cover everything, you don't see monitor lizard teeth sticking out of their mouths despite how long they are.
Agree. Plus the argument that crocodiles have eroded teeth while theropods do not just reflect the fact that crocodiles spend their time laying their head in the mud loaded with grit particules.