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Re: Size of *Neoceratodus africanus* and/or *N. tuberculatus*
Graydon <firstname.lastname@example.org> wrote:
> 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
Yes, but I think that the piscivorous adaptations of spinosaurids have been
over-emphasized. The comparative biomechanical analysis by Rayfield et al.
(2007) found the gharial (gavial) to be the closest modern analog for
_Baryonyx_, but they held off from arguing that spinosaurids were
dedicated/specialized piscivores. Sues et al. (2002) argue that, while fish
probably formed part of the diet in _Baryonyx_, "there is nothing to suggest
that spinosaurids were exclusively or even predominantly piscivorous".
I'm not trying to dispute the hypothesis that spinosaurids fed on fish. (After
all, the gut contents of _B. walkeri_ is prima facie evidence that they did.)
I'm only arguing against the hypothesis that spinosaurids were specialized
piscivores, or even that fish (including giant lungfish) were even a major part
of their diet.
As for the "big thumb claws" being an adaptation for catching ('gaffing')
Besides, an enlarged ungual of the first finger (pollex, or thumb) is also seen
in torvosaurids. Torvosaurids show no piscivorous adaptations in the skull.
Also, in spinosaurids (as in torvsoaurids) the forearm is quite short, which I
would interpret as poorly adapted for catching fish - especially if the animal
was not submerged. Speaking of which...
> 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 take your point; but I was talking more about aquatic (or semi-aquatic)
adaptations in general. If fish were a major part of their diet, and
spinosaurids entered the water to catch them, wouldn't we expect to see at
least some aquatic adaptations in the postcranium? Maybe
aquatic reptiles and mammals? Hippopotamids and indohyids (both suggested as
possible sister taxa to whales) show thicker limb elements as a result of
osteosclerosis, to improve bottom walking.