The Mystery of the Plesiosaurs

[Balaur]

Okay, sensationalistic title, but, I am curious. Somethings has been bugging me. Several things. First, are nothosaurs related to plesiosaurs? And when did the first plesiosaur appear? Second, what about the diamond shaped tails on plesiosaurs and pliosaurs, which ones would have them, which ones wouldn't? Third, I have heard Predator X was the largest pliosaur. Then I found that there was a pliosaur from the Jurassic of Dorset, that was bigger than Predator X. What was it?

I know we have a plesiosaur expert here. I just need clarification of these subjects. It is very intresting and can help me for my future reconstructions of the best marine reptiles that ever lived.

Thanks for any comments! 

[amargasaurus cazaui]

Oh good premise for a thread. I have little knowledge or information about those animals myself and would enjoy seeing where the thread goes, thanks for posting it .

[Balaur]

Oh good premise for a thread. I have little knowledge or information about those animals myself and would enjoy seeing where the thread goes, thanks for posting it .

No problem! 

[wings]

...First, are nothosaurs related to plesiosaurs? And when did the first plesiosaur appear?...

This should be a good place to start (http://dml.cmnh.org/1997Jun/msg00263.html).

[wings]

...Second, what about the diamond shaped tails on plesiosaurs and pliosaurs, which ones would have them, which ones wouldn't?...

For this question, if you would like an intro then go to this link (http://saurian.blogspot.com.au/2011/01/tail-fins-for-plesiosaurs.html) and the actual paper on here (http://www.marshall.edu/etd/masters/wilhelm-benjamin-2010-ms.pdf). Just start reading the paper from page 41 onward, I skimmed through it a little and I think one of the element to look for from this paper is the change of direction of the neural spines on the tail vertebrae as an indication of the start of the "tail fin" (I'm sure there is more to it but I think it's better for you to read it... ). This is not the first paper on the subject but I suppose the very first paper by Dame is quite hard to obtain...

On a side note, here is a paper on mosasaurs' tail fins (http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0011998) and a paper on possible integuments on these animals (http://www.plosone.org/article/info:doi/10.1371/journal.pone.0027343).

A rather good website to go to would be the "Oceans of Kansas" (http://www.oceansofkansas.com/).

[amargasaurus cazaui]

The "Oceans of kansas" web site is an excellent place to study these animals. It is maintained and authored by Michael Everhart, who I was fortunate enough to meet and have sign my copy of his book. He is a very knowledgeable man on the topic and quite well versed . I did make note he was also one of the consultants for the Carnegie Tylosaurus figure, so i had him sign one of those as well for me. One of the few meager benefits of actually living in Kansas

[tyrantqueen]

Sorry if this is the incorrect place to post this, but since we're on the topic of plesiosaurs and the like- where is a good place to find skeletal restorations? I've been searching everywhere but there is barely anything to be found. I am particularly interested in mosasaurs.

The only thing I could find that was near enough to what I wanted was this skeletal by Dr. Smith


That's only one species though...

[Gryphoceratops]

Just wait for Dr. Admin to see.  He probably can answer all of those questions for you!

[Balaur]

Sorry if this is the incorrect place to post this, but since we're on the topic of plesiosaurs and the like- where is a good place to find skeletal restorations? I've been searching everywhere but there is barely anything to be found. I am particularly interested in mosasaurs.

The only thing I could find that was near enough to what I wanted was this skeletal by Dr. Smith


That's only one species though...

Nope. This the the right place to post. Anything plesiosaur related! 

Just got back from school, so I am continuing to read the paper on the caudal fins, thanks Wings!

[DinoToyForum]

I can, but not right now. I'm on a research trip to Dorchester to study this guy  : http://www.bbc.co.uk/news/science-environment-14061347

There are a few more skeletal reconstructions on my website here, though I need to add more...: http://www.plesiosauria.com/line_drawings.php

[Balaur]

I can, but not right now. I'm on a research trip to Dorchester to study this guy  : http://www.bbc.co.uk/news/science-environment-14061347

There are a few more skeletal reconstructions on my website here, though I need to add more...: http://www.plesiosauria.com/line_drawings.php

AWESOME! I can't wait to find out more about him. Probably the most bada** that ever ruled the oceans! 

[DinoToyForum]

Sorry for the delay.

Yes, nothosaurs are closely related to plesiosaurs, they both belong to the same group, Sauropterygia. However, plesiosaurs are not direct descendants of nothosaurs, they just share a very close common ancestor. The first plesiosaurs occur in the late Triassic and the oldest diagnostic plesiosaur genera and species are from the Triassic-Jurassic boundary.

The presence of a tail fin in plesiosaurs is still a contentious topic. Several researchers are working in this topic, including myself.

The Weymouth Bay pliosaur from Dorset is known from a complete skull and is probably a species of Pliosaurus (based on current diagnoses for that genus).

Hope this helps!

[Balaur]

Sorry for the delay.

Yes, nothosaurs are closely related to plesiosaurs, they both belong to the same group, Sauropterygia. However, plesiosaurs are not direct descendants of nothosaurs, they just share a very close common ancestor. The first plesiosaurs occur in the late Triassic and the oldest diagnostic plesiosaur genera and species are from the Triassic-Jurassic boundary.

The presence of a tail fin in plesiosaurs is still a contentious topic. Several researchers are working in this topic, including myself.

The Weymouth Bay pliosaur from Dorset is known from a complete skull and is probably a species of Pliosaurus (based on current diagnoses for that genus).

Hope this helps!

Thank you so much! Don't worry about the delay, It was worth it.  I guess I should keep open as an official "Anything Plesiosaur" thread. Thanks Dr. Admin! 

[Balaur]

I am here to revive this topic. So, I have another question on Plesiosaurs. Could Cryptoclidus actually lay on land and bask and sleep on the shore or would it suffocate and have spent its entire life in the water?

[FUTABA]

(Just butting my way in). I think Cryptoclidus would most likely be fully aquatic. Considering it's hefty weight and inflexible torso aswell as, if, theoretically, it were to crawl about on the land, it's inflexible horizontal neck would mean it'd be dragging it's face along the ground all the time. Evidence for viviparous birth (live birth) has also been found in the genus Polycotylus, so it's pretty safe to assume most if not all Plesiosaurs gave birth to live young (as did the Icthyosaurs) so there wouldn't be any need to leave the water to lay eggs or anything.

As for sleep, I'd say the most likely thing would be that Plesiosaurs and Ichthyosaurs alike slept much in the same way Dolphins and Whales do. They let one half of their brain at a time relax into a deep sleep, while the other half remains alert, and alternate sides so they can still decide when to surface for breath. (Breathing is a conscious decision for these sorts of animals, unlike us, where it is involuntary of course). Therefore they never become fully unconscious but still get the rest they require. It's likely that if Plesiosaurs, Ichthyosaurs etc adopted this method of sleep then they would have one eye open at all times when sleeping, as this occurs with modern Cetaceans. Or of course I may be embarrassingly wrong.

[Horridus]

The evidence for live birth shows that plesiosaurs were fully marine. The old idea of them hauling themselves on to the shore was based on the assumption that they must have laid eggs on land, a la sea turtles.

[Balaur]

Just to clarify. I know that plesiosaurs gave birth to live young, but was wondering whether or not it was physically possible for it to be on land. I think I have my answer thouh. I appreciate your guys's help.