Re: Speculative dino species

[Michael Bruce Habib <mbh3q@cms.mail.virginia.edu>]

On Sat, 28 Jul 2001 09:04:00 -0700 (PDT) Morgan Churchill 
<mmcjawa@yahoo.com> wrote:
> 
>If we are doing a speculative scenario with no KT event, 
>we mustn't forget the Marine reptiles.  maybe Mosasaurs 
>invade freshwater environments, evolving into forms 
filling 
>the niches of todays crocodiles.  

I would imagine that crocs would maintain this niche, as 
they seem to have during the Mesozoic.  Mosasaurs would 
face a number of constraints regarding a semi-aquatic or 
freshwater existence, and crocs are well established in 
this niche.  Keep in mind that Mosasaur relatives 
(Varanids) are mainly terrestrial, with semi-aquatic 
members, so that lineage is more varied than it seems.

>Meanwhile, their marine 
>relative get even more serpentine and sea serpent like.  

There is evidence that the clade including mosasaurs got 
quite a bit more serpent like.  Namely, that snake origins 
may lie with this group.  The strongest evidence for a 
snake-mosasaur clade comes from the feeding apparatus.  
Take a look a the the paper:

The origin of snake feeding  
Michael S. Y. Lee, Gorden L. Bell, Michael W. Caldwell
Nature 400, 655 - 659 (12 August 1999)  


The other evidence comes from early snake fossils that seem 
to represent aquatic, rather than burrowing, ancestors 
(I will look for the citation).


>Maybe filterfeeding pliosaurs will evolve
A distinct possibility.  D. Dixon did something created 
a creature going with this line of thought.

I would also add that having a fair number of large 
dinosaur taxa still in existence might place different 
selective pressures on this theoretical aquatic system than 
the modern system.  For example, there would be large 
terrestrial prey to be gleaned from riversides in most 
parts of the world, so species in the Nile Croc and Saltie 
niches might be expected on most continents (at least in 
the tropics).

--Mike Habib
mbh3q@virginia.edu