Re: AMPHIBIOUS DINOSAURS

[Nick Longrich <longrich@stardot.com>]

On Thu, 21 Nov 1996, Darren Naish wrote:

> The 'marine sloth', _Thalassonectes_ (that may be spelt wrong), is a rather
> controversial form. De Muizon et al suggested that it was truly adapted for a
> life in the sea - it's tibia is longer than its femur for example ('classic
> marine adaptation' in mammals). While I'm pretty certain that it could swim if
> it had to, and it did eat kelp (it lived on a coastal desert plain), I don't 
> see
> why it couldn't just wander out at low tide to browse on the kelp, like some
> populations of deer and sheep do in the Scottish islands. No real evidence 
> that
> it was out there swimming around like a giant sea otter. In fact, with
> _Carcharocles megalodon_ out there, this may have been a tad risky.

        There was one completely marine kelp-eater, Steller's sea cow, 
which unfortunately was wiped out in the 17th century by Russian 
seafarers. I wonder if, however, it had not suffered previous hunting at 
the hands of the Alaska natives, who are capable whalers, to say nothing 
of their ability to hunt a slow-moving creature like the sea-cow which, 
according to Steller, was not even capable of diving. There is almost 
nothing today known of them except for a few fragments Stellar was able 
to save. It would be interesting to see if there are any fossils, 
however. 
        I hadn't heard the thing was supposed to be a kelp-eater though. 
I would have thought something more along the lines of sea grasses?
        This seems to be another niche strangely absent from the 
Mesozoic, the marine herbivore.