Mosasaur Ecdysis

[Squalicorax]

^I understand what you're saying here, Mike. I just thought that I read somewhere that Clidastes may have evolved from anscestors designed for a different lifestyle (possibly a more littoral one), and/or that the Clidastes-Mosasaurus line evolved for a fully aquatic lifestyle later than the Tylosaurs-Platecarpus line , either of which would explain its hindlimb and tail proportions. Then again, I could just as easily be mistaken and if so, I apologise.

Again, I have no problem with the idea that mosasaurs may have lost their scales late in their evolution, however, earlier on they must have (and as evidenced by the photographs did) retained them and if this is the case they must have found a way to shed their skin like all squamates, likely by shedding in a somewhat similar manner to their modern relatives, before evolving a more efficient means of getting the job done (if they evolved one at all as you've suggested, but that's another debate).

-Squalicorax

[Mike]

If I was a "little guy" like Clidastes, I'd want to stay as close to shore and in as shallow water as possible.... although some workers (Sheldon, for one) have postulated that Clidastes was actually an off-shore deeper water, deep diving species, based on bone density. Clidastes is generally believed to have reached lengths of 4-5 m, although I have recently seen specimens from Kansas that are as large as any Platecarpus (6-7 m). The body proportions of Clidastes (body vs tail length) are certainly different from just about all other mosasaurs... but as they evolved into larger forms (e.g. Mosasaurus) in the Campanian, the proportions became more like the "standard." The big difference to me seems to be in the limbs... In both Clidastes and Mosasaurus the limb bones are more robust with well developed articulating surfaces at the joints... In Tylosaurus/Platecarpus, we see much more cartilage in the limbs (the joints are mostly cartilage), possibly an indication that they were being used less and less.  On the other hand, Clidastes/Mosasaurus as you suggest may have been using their limbs much more for maneuvering in a littoral environment.... or as Lingham-Soliar has suggest, beginning to use them as "wings" for underwater flight, like plesiosaurs. Plotosaurus (from California) went a step further, and seems to have been becoming more like an ichthyosaur with a slimmed down body, nearly solid, paddle-like flippers and an expanded tail fluke. ...
http://www.oceansofkansas.com/Mosasaurs3/Plotosaurus.jpg

By the end of the Cretaceous mosasaurs were evolving in all kinds of directions... It would have been interesting to see what they would have been like after another 25 million years. However, I am pleased not to share our modern oceans with them! 

Mike

[Squalicorax]

Its absolutley fascinating how much Plotosaurus resembles an Ichthyosaur, convergent evolution, perhaps? I agree, its quite tempting to speculate what bizzare forms these animals would have evolved into had they not gone extinct (or at least so rapidly). Out of curiosity, is Plotosaurus theorized to have sprung from the Clidastes-Mosasaurus lineage or Tylosaurus-Platecarpus line?

Anywho, back on topic, perhaps mosasaurs with greater ties to land (such as potentailly Clidastes) would have retained their skin and shedding mechanism from their squamate anscestors before departing for deeper waters.

-Squalicorax

[Mike]

Not sure it adds one way or the other to the discussion, but here's a picture I took back in 2000 at the Denver Zoo showing a Komodo dragon in the process of shedding patches of old "skin" ... I would suspect this could be an model for earlier mosasaurs (Turonian-Campanian)...but probably "sheds" little light on their later evolution. 

Regards,
Mike

[Anthony]

Of all the little fishies from the chalk that could be removing those patches, I think Enchodus would be waaaay at the bottom of my list.

[Mike]

I would agree... definitely would not want Enchodus nibbling on me... Even the little ones had large fangs!  Mike