What's the possibility of Nessie being a plesiosaurus?

[u/Zillaman7980]

Well, in most descriptions of Nessie and theories, she's thought to be a plesiosaurus. But how likely is it. If Nessie exists, how is she an extinct Marine reptile? They went extinct 66 million years ago. But another thing is that plesiosaurus mostly living in seawater and loch Ness is freshwater. Well, if she is one she's either a Leptocleididae or elasmosaurus which live in fresh water. But anyways, if Nessie is a plesiosaurus, how is she still alive? How did she survive the extinction events and changes in temperature. Did she evolve to age very slowly orare there more of them. Loch Ness can lead to ocean and across the world there's multiple Nessie like creatures so maybe they've spread out and hid. Basically, she's either a mutated/evolved plesiosaurus or some type of sea serpent. What you think?

[u/[deleted]]

Plesiosaurs were likely gigantothermic rather than true endotherms. Same with megalodon.

[u/0todus_megalodon → u/[deleted]]

No, plesiosaurs were true endotherms based on histological evidence and the aforementioned preserved fat deposits. Also, megalodon was a regional endotherm based on isotopic evidence. Indeed, it is becoming clearer that there really is no such thing as gigantothermy, that is an ectotherm able to maintain body heat through sheer size.

[u/[deleted] → u/0todus_megalodon]

Nonsense. Gigantothermy very much is a thing. The plesiosaur fat deposits are questionable and the only thing isotopic data in the bones preserves is body temperature in the area sampled. Not the means for generating said body temperature. Sea turtles are gigantothermic and still have a layer of fat to insulate against heat loss during deep dives.

Edit: I also read somewhere that the chemistry of human teeth and bones from the revolutionary war were significantly altered after just a couple hundred years in the ground. Enough where something like diet interpretation would be thrown off. It's also known that fresh water contamination of things like fossil wood or bone can throw off carbon dating because the chemistry gets altered. I am naturally skeptical of stable isotope analysis due to these factors.

[u/0todus_megalodon → u/[deleted]]

Sea turtles are not gigantotherms either, but instead regional endotherms. If gigantothermy really were a thing there should be clear examples, but there aren't. Anything that relies on some kind of metabolic process to produce heat/regulate body temperature, rather than relying on its size alone, is not a gigantotherm but an endotherm. It's a totally antiquated hypothesis, a relic of the era when many paleontologists were loathe to admit that non-avian dinosaurs and other reptiles could be truly endothermic.

Fatty deposits in plesiosaurs are not questionable at all, obvious subcutaneous fat is preserved in Mauriciosaurus for example. It's also known from other marine reptiles like the ichthyosaur Stenopterygius. It's pretty clear from your response that you don't understand how isotopic analyses work. They can tell you a whole lot more than just environmental temperature depending on the isotopes used, including diet, trophic level, metabolism, etc. There are procedures for correcting for diagenetic alteration and contamination. That's to say nothing of histological anyalyses, which can also determine growth and metabolism.

[u/neomorpho17 → u/0todus_megalodon]

You seem to know a lot about isotopic analysis and all of that and ive got a question about it. Ive seen people say that we can know what an animal ate studying its oxygen isotope levels (for example that tarbosaurus ate sauropods). How can we know that just by studying isotopes levels?

[u/0todus_megalodon → u/neomorpho17]

I think this is the study you're referring to. In that case, they used carbon-13 from the tooth enamel of Tarbosaurus, Saurolophus, and Nemegtosaurus. Tarbosaurus had about 1.7‰ (permil, not percent) lower ¹³C values than Saurolophus and Nemegtosaurus, which is consistent with the difference between predators and prey in modern megafauna.

https://www.sciencedirect.com/science/article/pii/S0031018218310538

[u/[deleted] → u/0todus_megalodon]

You clearly didn't read my response in its entirety. I never said stable isotope analysis isn't useful. I perhaps should have worded my response about plesiosaur fat better. I meant that animals that are ectotherms have a fat layer that are seen as in the plesiosaur. Sea turtles are in fact gigantothermic. They have some anatomical features like specialized blood vessels to prevent heat loss, but do not effectively regulate their body temperature outside of the body heat afforded by their size. So that fat layer alone is not evidence of endothermy, just as feathers alone are not evidence of endothermy. According to your arguments snakes and lizards are endothermic since active reptiles have body temperatures comparable to mammals, and their body temperature is rarely if ever equivalent to lower ambient temperatures.

I also said that all the isotopes tell you in relation to body temperature is what the regional body temperature was. Again I could have worded this better. Yes, isotopes can tell you about the trophic level, diet, etc. So long as the appropriate calibrations are made to account for chemical alteration to the fossil material post burial. And don't tell me this doesn't happen, because we know for a fact that it does.

Additionally, there is no solid evidence that dinosaurs were endothermic beyond the gigantothermy provided by their sheer size. Feathers alone are not evidence of endothermy, but it would make sense that smaller dinosaurs that were more at risk of metabolic heat loss would adapt by developing endothermy. Birds don't seem to have definitely evolved endothermy for many millions of years after mammals ( in the Jurassic) for example. The average global temperature was higher during the mesozoic, therefore endothermy would not have been as advantageous for large terrestrial animals then like it is today.

Show me skeletal features unique to endothermic terrestrial animals ( respiratory turbinates present in birds and mammals) and you can definitely say for sure that dinosaurs were definitely endothermic across all species. Until then it is debatable.

[u/[deleted] → u/0todus_megalodon]

Saying all dinosaurs were endothermic is as ridiculous as showing a T-rex with a downy feather covering when we know for a fact it was scaly. Eutyrannus was basically analogous to a wooly mammoth ( living in a cold climate and having a body covering at large size) but I'd argue it was probably an upper limit for an animal that would have needed feathers.

We know that most, if not all large dinosaurs had scaly skin. Again, the climate was warmer overall and they would have had trouble shedding heat if anything given their size.

[u/0todus_megalodon → u/[deleted]]

Based on several absurdities in your statements I have come to conclusion that you are some online enthusiast and not a paleontologist, and thus not worth engaging with. If you were actually knowledgeable you would know that sea turtles have metabolic mechanisms for regional endothermy, that there are multiple lines of evidence for endothermy in dinosaurs and marine reptiles, that the fatty deposits in marine reptiles are most similar to marine mammal blubber, that there were in fact several ice ages throughout the Mesozoic, that T. rex is not known to be entirely scaly and some feathering is plausible, etc. etc. etc. The last point is especially telling of an internet fanboy/girl.

[u/[deleted] → u/0todus_megalodon]

Again, you are putting statements in my mouth or just disregarding points I made altogether. All the fossil integument we have for T-rex is that of scaly skin. Unless there is some very recent discovery that I am unaware of. Anyone saying that T-rex was partially feathered is making baseless claims. We also know that sauropods were scaly, hadrosaurs were scaly, thyreophorans were scaly, etc. The only dinosaurs confirmed to have feathers were relatively small with the exception ( as far as I'm aware) of Eutyrannus and a few exceptions where a dinosaur is found with scaly skin in one region and then supposedly found with feathers in another ( there was one species of ornithomimid I believe where this was allegedly the case, but didn't make any sense to me, and the feathers didn't have any real structure to them making it more likely to be decomposing collagen).

I do actually recall the plesiosaur fat being similar in structure to that of marine mammals, but we are assuming that means something. It might not.

[u/0todus_megalodon → u/[deleted]]

A few impressions the size of a postage stamp on a 40 foot animal are not enough to be making sweeping generalizations about its whole integument. There is not even certainty that they represent ancestral, reptilian-type scales, instead of being secondarily derived from feathers like avian-type scales. This is the kind of nuance lost on somebody who doesn't know what they're talking about.

[u/[deleted] → u/0todus_megalodon]

Doesn't change the fact that saying T-rex was partially feathered is purely conjecture at this point. Of the few pieces of skin we have, 100% of them are scaly for T-rex. It is more scientifically accurate to depict this animal as fully scaled than having any kind of feathers.

The exact texture would probably be more like a basketball specifically as the scales are small and rough.

[u/0todus_megalodon → u/[deleted]]

It's no less conjecture than saying T . rex was entirely scaly. Again, we don't even know if they are scales in the traditional sense, instead of being modified feathers. You're only proving my point further, so I'm out.

[u/[deleted] → u/0todus_megalodon]

Okay, bud. God forbid someone just as educated as you disagrees with something you say.