Theropod (and maybe other dinosaurs) skin/muscle discussion.

[Kohler Palaeontology]

Hello forum,

 

I watched a video recently that some other members may have watched about the most up-to-date, accurate depiction of T.rex.

The model in the video, instead of having a fleshy muscle at the corner of the mouth, it proposed that T.rex, and maybe other therapods had a jowl of skin that covered this (it appeared like No. 2 in the image below).

 

As a paleo artist, I would like to know everyone else's opinions.

 

I don't know much about this study or if there is a paper on this.

 

But here's a very basic drawing of 3 different depictions.

 

 

 

What do you all think is the most likely?

 

[Jaybot]

Yes, I saw that same video.  T-rex is one of the dinosaurs whose paleoart always seems... off.  (at least to me )

While extinct creatures may have had very different features than all extant animals, it is still reasonable to base reconstructions off of living examples.  (imagine our confusion if the echidna was extinct).

 

Here is a Comodo dragon, with jaws nice and wide open.  These and other lizards make me lean to option #1.

 

 

 

 

Another thing to keep in mind, that this supposed 'most accurate T-Rex depiction' is not universally accepted.  It is, after all, a very nice reconstruction based off of the latest papers, and also for sale.

[Kohler Palaeontology]

Thanks for the reply!
 

I think I'm probably going to keep reconstructing the lizard/crocodilian look.

And yeah, T.rex is just one of those dinosaurs to the point where there's just so much paleoart out there about it, that a lot of it does seem off. And a lot of depictions some like, whilst others completely don't. Hopefully we can find a rex mummy one day!

Edited December 9, 2024 by Kohler Palaeontology

[Jaybot]

If you don’t mind, we’d love to see the results!  I like paleoart  

[Kohler Palaeontology]

33 minutes ago, Jaybot said:

If you don’t mind, we’d love to see the results!  I like paleoart  

I might make a post sometime in the coming weeks on my paleoart. I just made this discussion for future art, not anything particular. Although I'm working on some stuff at the moment, Which I may show soon. 

[BirdsAreDinosaurs]

Did they present evidence for the second option in the video? If not, I do not see much reason not to stick to option #1, although #3 also seems quite plausible.

[Kohler Palaeontology]

They claimed that (for option 2) "when they tried to restore the amount of musculature that should be at the back of the jaw on T.rex. the outer most skin folding didn't have enough space to be contained. So, they suggested that it's more likely that T.rex's outer most skin fold extended down from the jugal region under the eye and sort of backwards and across the rear end of the mouth, kind of like what we see in living condors".

 

 

[Kohler Palaeontology]

I don't know if there's been an actual study on these subjects or not.

 

but the reconstruction also proposes that theropods had their teeth partially covered by gum tissue, like monitors. Monitor lizards have huge teeth comparable to their body size. But you can barely see them because there mostly covered up by gum tissue.

[BirdsAreDinosaurs]

12 hours ago, Kohler Palaeontology said:

They claimed that (for option 2) "when they tried to restore the amount of musculature that should be at the back of the jaw on T.rex. the outer most skin folding didn't have enough space to be contained. So, they suggested that it's more likely that T.rex's outer most skin fold extended down from the jugal region under the eye and sort of backwards and across the rear end of the mouth, kind of like what we see in living condors".

 

 

Thanks! Sounds quite possible, who knows. But I think more rigourous studies are needed to be able to draw conclusions. I must say the head of the Eofauna T. rex (I found and watched the video) has some dog-like qualities that I am not really a big fan of, but maybe I am just used to more inaccurate depictions.

[BirdsAreDinosaurs]

12 hours ago, Kohler Palaeontology said:

I don't know if there's been an actual study on these subjects or not.

 

but the reconstruction also proposes that theropods had their teeth partially covered by gum tissue, like monitors. Monitor lizards have huge teeth comparable to their body size. But you can barely see them because there mostly covered up by gum tissue.

Yeah, sure that is a possibility as well. But I think many people will feel some resistance to this idea, as it will make theropods look much less menacing.

 

All hope is on Spinosaurus for a lipless theropod with exposed teeth  

[North]

I would lean towards 3 and 1.

Thinking it more like mouth of an bird or reptile.

And definetly some gums and lips.

[Kohler Palaeontology]

1 hour ago, BirdsAreDinosaurs said:

Yeah, sure that is a possibility as well. But I think many people will feel some resistance to this idea, as it will make theropods look much less menacing.

 

All hope is on Spinosaurus for a lipless theropod with exposed teeth  

Yeah. I just don't really see how an animal with 6-inch teeth sticking out could have them covered by gums. Also. Monitor jaw anatomy is very different to theropod. And it allows the presence of this kind of soft tissue (and obviosly, those lizards were smaller than rex. I wonder if Megalania could've covered all of its teeth with gingiva).

 

Lizard jaws, when they close, don't completely occlude to each other. While on dinosaurs it fully closes so far that sometimes the teeth go below the lower jaw. But, on lizards, if they closed their mouth in the same way theropods do, it would cause them to bite completely through their gum tissue (the gingiva and labial oral glands) ... OUCH! So, when they close their jaw, there's a gap (which is on all lizard skulls I've seen, but I don't recall seeing a theropod skull like that). And, on lizards the palate is not very deep. But, on theropods, it is really deep to store the lower teeth.

 

I made this basic diagram to show the gingiva on lizards vs rex.

 

The red line on all the skulls is where the lips meet. Also, the VAST majority of lizards have a jaw like the Gila Monster (with the gums). So, you can see how much of the gingiva covers the teeth on lizards, but on T.rex, it doesn't. To me, if T.rex had their teeth covered by gingiva, you would have to reposition the ectopterygoid bone and other bones and even the lower jaw itself! You know. You might even have to re-shape T.rex's maxilla bone to be more curved inward, not outward toward the lower jaw. And, with how bit this animal is, I really can't see how all of that gum tissue would work with the weight of it all. And yes, they would look really weird.

 

 

[North]

Also thinking about the size difference between t-rex teeth, full gum sheets feel quite extreme.

For some reason I always imagined gumline going somewhere around here.

[Kohler Palaeontology]

Definitely makes sense. As the root of the teeth seem to be exposed slightly, so the gums probably covered that up. And yes, on lizards the teeth remain relatively the same size, a lot of the time it's almost exact. One rex, you might have a tooth that's only a couple inches inch sticking out, and another might me 6 inches, and both of those teeth might be right near each other. And theropod teeth are really straight, on monitors they curve outward slightly when looking at the top of the skull.

Edited December 11, 2024 by Kohler Palaeontology

[BirdsAreDinosaurs]

11 hours ago, Kohler Palaeontology said:

Yeah. I just don't really see how an animal with 6-inch teeth sticking out could have them covered by gums. Also. Monitor jaw anatomy is very different to theropod. And it allows the presence of this kind of soft tissue (and obviosly, those lizards were smaller than rex. I wonder if Megalania could've covered all of its teeth with gingiva).

 

Lizard jaws, when they close, don't completely occlude to each other. While on dinosaurs it fully closes so far that sometimes the teeth go below the lower jaw. But, on lizards, if they closed their mouth in the same way theropods do, it would cause them to bite completely through their gum tissue (the gingiva and labial oral glands) ... OUCH! So, when they close their jaw, there's a gap (which is on all lizard skulls I've seen, but I don't recall seeing a theropod skull like that). And, on lizards the palate is not very deep. But, on theropods, it is really deep to store the lower teeth.

 

I made this basic diagram to show the gingiva on lizards vs rex.

 

The red line on all the skulls is where the lips meet. Also, the VAST majority of lizards have a jaw like the Gila Monster (with the gums). So, you can see how much of the gingiva covers the teeth on lizards, but on T.rex, it doesn't. To me, if T.rex had their teeth covered by gingiva, you would have to reposition the ectopterygoid bone and other bones and even the lower jaw itself! You know. You might even have to re-shape T.rex's maxilla bone to be more curved inward, not outward toward the lower jaw. And, with how bit this animal is, I really can't see how all of that gum tissue would work with the weight of it all. And yes, they would look really weird.

 

 

This is an interesting read: http://markwitton-com.blogspot.com/2023/03/new-paper-fresh-evidence-and-novel.html?m=1

 

The author points out that a mouth resting posture like the one you show for T. rex is probably impossible and the gape would be more relaxed. He also mentiones that not much is known about theropod gums, but extant lipped reptiles have at least 25% covered and Paul (2019) argues for monitor-like conditions for theropods.

[Kohler Palaeontology]

32 minutes ago, BirdsAreDinosaurs said:

This is an interesting read: http://markwitton-com.blogspot.com/2023/03/new-paper-fresh-evidence-and-novel.html?m=1

 

The author points out that a mouth resting posture like the one you show for T. rex is probably impossible and the gape would be more relaxed. He also mentiones that not much is known about theropod gums, but extant lipped reptiles have at least 25% covered and Paul (2019) argues for monitor-like conditions for theropods.

Thanks! I'll check it out tomorrow, bedtime here almost.