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Pliosaur-Plesiosaur difference


RuMert

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Hi, 

How can you tell by isolated bones, besides the skull, if you see a pliosaur or plesiosaur remains? 

Any obvious differences in paddle bones or vertebrae? Triangular teeth? Does it all depend on the given species?

Thanks

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From what I know, bones are difficult to distinguish (maybe on size) , so I'm curious what others gonna say. Teeth are easier I guess, plesiosaur is more slender than pliosaur? 

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This is going to be very difficult with isolated bones. Also just for accuracy sake, pliosaurs are nested within the plesiosaurs, so what you're really asking is how to distinguish between pliosaurs (Pliosauroidea) and other members of the Plesiosauria. Because of this close relationship their bones are going to be very similar. A good place to start would be to search the literature and see what anatomical features are used to define the clade Pliosauroidea, and how these differ to the defining characters of the other plesiosaur groups. Of course this requires you to have the specific bones that contain these characters, in order for you to observe them and make an informed decision. As Natalie said, with teeth it is easier because pliosaurs tend to have more prominent ridges running along the crowns than other plesiosaur teeth. Pliosaur teeth also tend to be much broader and more robust, while teeth from elasmosaurids for example are more slender and smooth-surfaced. You mentioned triangular teeth in your post. I think you are referring to the trihedral teeth of Pliosaurus? This is a feature that is specific to that genus, so if you have a tooth like this, then that is one scenario where you would be able to give a good ID. Then of course there's always the option of narrowing down what something could be based on the known fauna of that particular formation or region. Size may work for areas where large pliosaurs are accompanied only by smaller plesiosaurs, but some of the elasmosaurids for example also got huge, so a large bone doesn't necessarily indicate one way or the other in this case. 

 

Edit- I've quickly checked and it seems Pliosauroidea is not defined using anatomical characteristics, but rather using inferred common ancestry. So there isn't going to be any defining pliosaur features you could look for sadly! 

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5 minutes ago, RuMert said:

Thanks, that was comprehensive. I'll try narrowing the cirlcle of possible species and then reading papers with their description if available.

It's not an easy thing, I'm also trying to learn more on the plesiosauria. If you find informative papers,  a link or copy would be appreciated :) 

 

Natalie 

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Hey :) 

The Plesiosaur Directory might be a useful resource for you - it contains quite a good bit of information concerning the anatomy, taxonomy etc of plesiosaurs. I'd say that the info on the website is very trustworthy, given that the man behind it (Dr Adam S. Smith) is an authority on Mesozoic marine reptiles

Hope this helped!

-Christian

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5 minutes ago, The Amateur Paleontologist said:

Hey :) 

The Plesiosaur Directory might be a useful resource for you - it contains quite a good bit of information concerning the anatomy, taxonomy etc of plesiosaurs. I'd say that the info on the website is very trustworthy, given that the man behind it (Dr Adam S. Smith) is an authority on Mesozoic marine reptiles

Hope this helped!

-Christian

Thank you very much for the help, Christian! I will check this :D

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Polycotylid cranial anatomy.pdf

Druckenmiller 2002_Edgarosaurus.pdf

 

I'm not finished... Some of these papers are rather big ;)

-Christian

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Albright etal2007Utah polycotilyds.pdf

That's about it - hope some of them will be helpful :)

-Christian

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27 minutes ago, The Amateur Paleontologist said:

Albright etal2007Utah polycotilyds.pdf

That's about it - hope some of them will be helpful :)

-Christian

Awesome! Thank you, Christian! 

You are my hero of the day :raindance:

 

One more question: do you know if plesiosaur remains are found in the department du Jura in France? 

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48 minutes ago, Natalie81 said:

Awesome! Thank you, Christian! 

You are my hero of the day :raindance:

Glad I could help :) 

 

49 minutes ago, Natalie81 said:

One more question: do you know if plesiosaur remains are found in the department du Jura in France? 

The only reference to plesiosaurs from the Jura is this article from 1998... Marine reptile Jura trace fossils.pdf - I'm not sure about other more substantial remains of plesiosaurs from that department... 

Places like the Vaches Noires are much better for finding plesiosaur remains - or even the region of Lorraine (which yielded the remains of a Simolestes pliosaur - and is a bit closer to Jura...)

 

-Christian

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https://archive.org/details/biostor-118792/page/n1

A classical review. Among other things it says Pliosauridae are characterised by short cervical vertebrae and elongated bones. Distinguishes species by verts (pictures provided). Not very up-to-date, but still an interesting read.

 

https://www.academia.edu/26478188/Giant_Pliosaur_Reptilia_Sauropterygia_from_the_Late_Jurassic_of_Kazakhstan_and_Some_Remarks_on_the_Systematics_of_Pliosauridae

Another vert difference review

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