So, did theropod dinosaurs have reptilian style lips, or did they freeball it with exposed teeth?
Reasons for lips:Many dinosaurs appear to have pitting along their jaw line that appears homologous to the pitting that anchors the lip tissue of lizards. Enamel is stronger when it is kept moist. Exposed enamel can grow brittle or get infected. Crocodiles have a certain enamel wear pattern from having exposed teeth that we don't see in dinosaur tooth fossils. Some theropods have fairly long tooth 'lifespans' before replacement. Any damage to a tooth could be very problematic. Ornithischian dinosaurs are assumed to have had cheek pouches. Multiple theropod lineages are secondarily herbivorous and likely had cheek pouches. This would have had to have been developed independently. Some theropod dinosaurs may have had difficulty closing their mouths fully because of their tooth size. Lips would cover this. Reasons against lips:Lizards are not closely related to dinosaurs and are not often used as analogs in other situations. Neither crocodiles nor birds have lips.Some say that the pitting pattern found on theropod faces is not as lizard-like claimed. Certain species of theropods clearly had dental arrangements like interlocking teeth that would not have possible with lips. They would have had to evolve to not have lips. Uncrushed theropod skulls have been found that are comfortably fully closed without damage. Some theropod skulls appear to have recesses in the top of the mouth that would accommodate teeth. Theropod tooth wear patterns don't indicate that they would have even rubbed on one another. Theropod mouths are generally very large. Did I miss anything?
No lips or skin or flesh. Dinosaurs were always skeletons.
>>5133890We know for a fact that the bottom image is wrong not because it has lips, but because Saurischian skulls completely close like a box. It doesn't look like it should do that because in the skull without tissue - just the fossil alone - bone would be touching bone but that's how we find them, and that's how the cranium and the mandible fit together. So we know that their skulls totally closed and the tissue covering the parts that contacted must have been very thin. And recently it's been talked about a bit how there are indentations on the roof of Tyrannosaur mouths to fit the lower teeth. That's because of how tightly closing the mouth is. We also know that the little front baby kitty teeth of Tyrannosaurus were used to scrape meat off of bones which means they have to have been at least partially exposed. The only alternative to that is that Tyrannosaurs had soft lips like a mammal, and no reptile has lips like that. There's also the fact that multiple theropods have maxillary teeth that when the mouth is shut appear to go below the bottom of the chin in their longest lengths. This would be impossible if those teeth were encased in lips, unless the mouth were held ajar from the perspective of the bones. And again remember, we know that the skulls close entirely like a box in these animals. So from the evidence we have it looks like lips in dinosaurs other than Ornithischians (though that's more cheeks than lips) just didn't exist the way that people want to depict them. I think it's likely that Saurischians had lips more like crocodilians which would make sense since they're related. How tightly their jaws close would also explain how they kept the interior of their mouths moist without having lips or living in water. One thing's for certain - they absolutely did not have lips like Lepidosaurs (Tuataras and Squamates). Dinosaur skulls, tooth attachment, the whole thing is totally different from these animals.
>>5133892I actually didn't read any of the thread responses before I gave mine but yeah you covered some of the things that I mentioned. It should be noted that foramina in the skull mean absolutely nothing. All that means is that there are holes in the bone to admit passage for nerves or blood vessels. That's it. It doesn't tell you anything about the lips of an animal.
Another thing to note is that the foramina on the skulls of Tyrannosaurus are more diffuse as in a crocodilian compared to the straight line of formina along the edge of the jaws of lizards. They also seem to be concentrated on the bottom of the chin and the front of the snout which heavily implies that they're nerve foramina, and not for blood vessels necessarily. Again, these are related to crocodiles so it makes sense that they would be using similar organs to sense their environment.
>>5133998Surprisingly, we’ve got someone getting it correct off the bat. This duff about tooth enamel and foramina counts misses the point. It’s about the jaws and the function of the teeth. If we can be confident about how the jaws fit together and how the teeth were used, then the pieces fall into place. No lizard lips - but perhaps lips covering part of the teeth on the upper jaw. I imagine that the lower jaw had no extra oral covering, as, like an alligator, it sat completely inside the upper. The fossils tell us this.
>>5134238
>>5134239
>>5134241
>>5134245Compare these with Komodo dragon skulls. Maybe a slight overbite, but very slight, and only in width. The lowers don’t sit within the uppers - they meet them.
>>5134249Hell, the original Sue skull (which Witton’s illustration in OP is based on) conveys this, tho it is badly crushed and shouldn’t be the make or break of the discussion.
>>5134250Compare even Sue’s (badly) restored skull in pic related to witton’s illustration. He is fudging how close the upper and lower jaws are in length.
>>5133892that image is excellent
>>5133998>>5134238could it be possible that they had fleshy lips designed specifically to cover the teeth despite the odd arrangement? baring teeth is still rather rare so exploring adaptations of difficult-to-fossilize fleshy material should still be done, imo. Has there been any research into such difficult to detect structures?
>>5134278Lips of some form are still likely, they just wouldn’t be identical
>>5134278I've always thought that these lips looked the most accurate. Somewhat covering the teeth but leaving them mostly exposed very similar to a crocodile. I also like how the scaling on the face looks more like a real reptile instead of microscopic pavement scaling or bizarre looking mishmashed textures that don't look realistic for anything alive like a lot of paleoartists have created in papers.
Wtf how is this thread completely reasonable and not schizophrenic at all? I entered it expecting shit flinging, but this is a nice surprise
>>5134298My asspull theory for tyrannosaur facial integument is the maxilla (and perhaps the rest of the face) was covered in thick keratin like we see on crocodilians. At least around the mouth. The formina seem pretty well spread out, and we know tyrannosaurs cracked through bone and bit one another's faces (probably in spars for mates and territory). A thick keratinous sheath on the face would have been very good protection. The top of most tyrannosaur heads appears roughened, which is another trait that can denote keratin attachment.
>>5134416That one alcoholic nutcase that always posts this selfies either died of alcoholism, fucked off or got banned permanently somehow. Or maybe his therapist just gave him sedatives or something. He was like 98% of the shitposting on this board. I'm convinced. If you look at the catalog you'll also notice a distinct lack of cat hate threads. Very interesting.
>>5134420Well we already saw that idea get blown the fuck out with Triceratops. That kind of grooving just means blood vessels go there. It doesn't mean a fingernail is attached. I think it was just scales, but I think the scales were larger than people think. Like the picture that I posted of that PNSO toy.
My problem with total lipless-ness like Crocodiles is that the Crocodiles lack of lips seems to be a very specific aquatic foraging adaptation that involves prey capture via rapid side to side snaps. They have long jaws so they have more reach to capture prey from further away, long conical teeth that help to grab and hold onto prey, and finally lipless mouths that allows water to pass through their open jaws causing less fluid drag when they make that lightning fast snap underwater. You can test this yourself by filling bowl with water and getting a fork(lipless toothy mouth) and a spork(lipped toothy mouth) and see which one offers less resistance to stirring. When you live in murky waters where you can barely see 2 feet in front of you it helps to be able to grab any passing meal as fast as possible. It's not just Crocodiles that have this adaptation either, we see the same adaptation in Gars and certain kinds of River Dolphins. One group of Dinosaurs that are likely to have a totally lipless condition are Spinosaurids and especially Spinosaurus itself since more and more evidence points towards it having a marine lifestyle. However for other terrestrial Dinosaurs like Tyrannosaurus it doesn't make much sense for it to possess these features. That's my argument against total lipless-ness in terrestrial Dinosaurs but I do think the alternative lipped conditions proposed in this thread may be possible.
I'm just watching the debate, desu. Both sides make compelling arguments. Used to lean slightly towards lips, but after being reminded that dinosaurs replaced their teeth (retarded thing to forget, I know), liplessness looks a bit more compelling now.The alternative/partial 'lips'/tooth covering proposed here are interesting as well.
>>5134454To be fair, lizards replace teeth and have lips. It is only mammals that lack the ability to constantly regrow teeth (potentially an artifact of spending like 190 million years at the bottom of the food chain living very short lives).
>>5134416I posted >>5134278 and I fully expected 30 replies calling me a schizo or something by the time I came back, I'm very pleased.
>>5134416I believe (hope) paleoschizo overdosed and died
>>5134437I think the grooves in triceratops are different from the grooves talked about by anon (if I understand them correctly).The triceratops grooves are very clearly channels in the bone (pic related is a Rando’s trike chunk)
>>5134453You're forgetting that Dinosaurs and crocodilians both evolved from the Proterosuchids, which were very crocodile-like animals. And both crocodilians and Spinosaurids evolved lipless jaws. You have to explain how that occurred if they originally possessed lips. Theropods are also the most plesiomorphic of the dinosaurs which means they've retained the most primitive structures, so it's likely what they possessed is what they more or less came pre-installed with.
>>5134492Hi, paleoschizo here. Most of the posts in this thread are mine. Weird, huh? But do you know what's missing? I'll let you think about it. But then I already explained it, didn't I.
>>5134437>>5134498Whereas this pic of AMNH skull shows the rough texture I think Anon is referring to. This is more a raise series of ridges - formed by the bone being raised, rather than a series of channels for blood vessels. It could be evidence for heavily cornified, rough skin, or could be for ornamental scales, or maybe even both.
>>5134498Not really. They're pretty much the same thing. They're clearly indentations for blood vessels beneath the integument. And the piece you're showing is heavily eroded. I think midwits should stop coming up with ideas about dinosaurs they think sound clever. They've proven time and again that they can't be conservative or figure these animals out. Every time a new theory comes up it's proven to be retarded within about 5 years
>>5134501This image isn't very high quality, but even here you can see the channels of blood vessels. That's what I'm talking about. The rugose texture doesn't really mean anything. People have been trying for about a decade to convince themselves that anywhere they see rugose bone that means there must be some kind of fingernail attached to the face. It's simply not true. Dinosaurs are much easier for the most part than people want to make them sound. Like most things it's mostly people lying and making shit up, instead of looking at the actual evidence that are making the issue complicated. Where a T. rex skull looks like there should be horn there probably was horn and where it looks like there shouldn't be horn there probably wasn't.
>>5134503Let's also not forget that crocodilian skulls are extremely rugose and their faces are just covered in scales. It's kind of amazing to me how fast paleontologists forget that living animals exist and they can be compared to dinosaurs. Particularly crocodilians. It seems to be a very convenient group of animals to forget when studying dinosaurs because they tend to shit all over pet theories. This comes up in the claim that they're a pods can't pronate their hands for example. Crocodilians do it just fine. It's just not at a 90° angle.
>>5134502It’s actually not the same at all. Triceratops frill has a very distinct texture that is instantly recognizable to people who actually collect fossils. That is because of the very obvious pitting and grooves. No one who actually touches fossils would every get a piece of rex maxilla and a trike frill confused.
>>5134504The scales on Crocodilian faces aren’t the same as the scales on their body. They’re actually more akin to heavily keratinized skin. From Milinkovitch et al 2012:>contrary to skin appendages in other amniotes (as well as body scales in crocodiles), face and jaws scales of crocodiles are random polygonal domains of highly keratinized skin, rather than genetically controlled elements, and emerge from a physical self-organizing stochastic process distinct from RDMs: cracking of the developing skin in a stress field. We suggest that the rapid growth of the crocodile embryonic facial and jaw skeleton, combined with the development of a very keratinized skin, generates the mechanical stress that causes cracking.
>>5134505Nobody said they would get them confused. But they are analogous structures. It's literally just grooves for blood vessels.
>>5134507Yes, but they are still scales. It's not a giant fingernail plate. They're just scales.
>>5134508They’re not - it’s a hummocky texture not analogous to grooves for blood vessels. It varies across tyrannosaurs. Carr (of all people) pointed this out correctly in 2017 in the D. Horneri description when he likened it to thickened skin. They agree with known osteological correlates.
>>5134511Can you read? They are developmentally distinct from scales. They’re more like structural cracks in the animal’s skin. Keratinized skin /=/ a fingernail. Scales are keratin, hair is keratin, feathers are keratin. It is integumentary variation. Croc face “scales” are not genetically controlled - reptile scales are, almost by definition. They occur in distinct bands and have serial homology. That’s why herpetologists can use them to inform taxonomy.
>>5134499Proterosuchids also have very different skulls compared to Crocodilians, Spinosaurids, and other animals that did side to side snapping which implies they were feeding in a different way with their serrated teeth and bizarre hook. Lipless jaws had to have evolved separately in both Crocodilians and Spinosaurids.
