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Re: Size of *Neoceratodus africanus* and/or *N. tuberculatus*



On Sat, Mar 28, 2009 at 08:59:19PM -0700, Tim Williams scripsit:
> David Marjanovic wrote:
> > Also, there's evidence from jaw mechanics, too, that spinosaurs were
> > "herons from hell".
> 
> I agree that spinosaurids were heron-like in their generalist-predator
> abilities; but they were not at all heron-like in their wading
> abilities.  I don't doubt that _Spinosaurus_ could have preyed upon
> giant lungfish or coelacanths in its habitat.  These mega-fish
> certainly offered a huge source of protein to a predator.  But I do
> very much doubt that _Spinosaurus_ was *specialized* for feeding on
> fish like these.

There's a big difference between "dedicated piscivore" and "has
adaptations for piscivory".

Spinosaurids do seem to have some adaptations for piscivory. (At least,
the big thumb claws and the jaw morphology would seem to argue for
this.)

> If _Spinosaurus_ was a dedicated piscivore with a preference for
> lungfish or coelacanths, why doesn't it show any aquatic/wading
> adaptations?  Instead, the postcranium tells us that spinosaurs were
> dryfooted landlubbers.

Does it _need_ wading adaptations?  Multi-ton animals have a lot of
trouble walking on top of the mud no matter what their feet look like.

> I'm aware that grizzly bears, which are terrestrial, are capable of
> catching fish from the shoreline - but it doesn't feed on fish all of
> the time.

Bears don't eat fish all the time, but the seasonal fish-feed is
ecologically very important for a number of bear populations.  Bears
also have a number of adaptations that might be selected for in a
context of the seasonal piscivory; they dive quite well, for example.

-- Graydon