Re: Wetlands Quadrupedal Dinosaurs

["Matthew Bonnan" <mbonnan@hotmail.com>]

Jaime:

You said:
>   The prescence of *Euoplocephalus* et al. in the
> Judith River Wedge (arguably a "Louisianan
> environment") would seem to support the prescence of
> massive, multi-ton (heavier than hippos and water
> buffalo, either *Syncerus* or *Bubalos*) and they may
> even have been semi-aquatic. With those guts, they
> certainly could have floated!

Umm ... well, while I don't think that dinosaurs were as hydrophobic as some 
folks have made them out to be, low-slung, heavily-armored dinosaurs don't 
seem to fit the bill for semi-aqautic dwellers.  Their feet don't seem 
particularly splayed like a hippo's and their heavy armor would seem to be a 
hinderance in water -- how does one surface to breathe?  Hippos not only 
have specially adapted limbs and splayed feet, but also do not have armor 
and have large, dorsal nostrils.

While you do find Euoplocephalus in Judith River sediments which suggest a 
deltaic environment, how do we know that they aren't the carcasses of poor 
suckers who drowned in a river or estuary and then were transported to and 
buried in the deltas?  The heavily armored carcass may have prevented it 
from breaking up as quickly as others and may have protected it from 
smashing into rocks on the way to its final burial place.

I dunno, but I would take a long hard look at the limbs and feet (as you 
would predict), but also the teeth to get some ideas about diet.  Also, most 
mammals have relatively flexible vertebral columns that flex in a 
dorsoventral plane which may allow hippos (I don't know for sure, so check 
me on it) to "bound" or "run" under water.  The armored thyreophorans, in 
contrast, seem rather limited in their body movements by their armored 
bodies, squat limbs, and heavy tails.  It would appear to me that the only 
time armored dinos like Euoplocephalus went into the water was when it was 
shallow enough to drink or bathe in, or when they drowned.

Sorry to rain on your Euoplocephalus parade into the deep blue sea,

Matt Bonnan
Dept Biological Sciences
NIU



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