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Re: What did Spinosaurus eat? New species of Lepidotes found



On 2/28/2011 1:07 AM, Tim Williams wrote:
The gavial is a longirostrine crocodilian in
which the rostrum ends in a terminal 'rosette' - as in spinosaurs.
The thing is, in order to catch fish, the gavial favors lateral
sweeping strikes with its rostrum.In fact, the longirostrine snout
appears to be specialized for this kind of predation: rapid movement
through water by lateral flexion, with the prey caught at the end of
the rostrum (McHenry et al., 2006; Anat. Rec. 288A: 827-849).  If this
also applied to spinosaurs, this is inconsistent with a heron analog
for spinosaurs, because herons employ stabbing motions with their
rostrum to procure fish.

Granted, the heron analogy is obviously incomplete or even wrong in some details, but gavials are limited by their anatomy entirely to lateral strikes, are they not?

The gravity-assisted downward "stab" is not possible for a gavial, and a tail-assisted forward thrust is unlikely to be quick enough to be successful against an evasive fishy prey. Also, the logic of evolution does not permit the heron to have a rosette, for reasons entirely unrelated to catching fish.

Therefore, the proposition that rosettes are only useful in lateral strikes, and could not evolve within other planes of attack, does not seem valid.

Er, not that you are explicitly stating that, but it seems to follow from your post, so I thought point below should be made.

As a matter of common sense, it can't be argued that a spinosaur standing "knee-deep" in water could not reach down and grab an unwary fish, anymore than it could be argued that a spinosaur "eye-ball deep" could not grab one w/ a sideways nip.

As an aside -- I have seen gators use the eye-ball-deep sideways nip to catch size-able large-mouth bass (est. 1-2 lbs) more than once, but mostly in heavy vegetation, e.g., hydrilla.