Re: More Suchomimus thoughts..

["Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>]

Patrick Norton wrote:
>If Sereno et al are correct that the "robust forelimbs" of Suchomimus
>evolved before the elongated snout and other possible fish eating
>adaptations, it seems a bit backwards to be attempting to explain the
>forelimbs as adaptations to a piscivourous diet.
        A) That is a big "if", relying as it does on their previous
assertion of a sister-group (_sensu lato_) relationship between
"torvosaurids" and spinosaurids. This hypothesis has not, to my knowledge,
found support in other studies, and I do not believe that it was explicitly
tested in this paper. In all fairness, the authors are correct in their
criticism of Charig and Milner, in that the latter authors merely dismissed
their conclusions rather than testing them. On the other hand, Sereno et al.
are similarly remiss in not addressing Charig and Milner's criticism that
they prematurely coded untested clades as OTUs.
        B) Is it just me, or don't those arms seem a bit short for fishing?
Maybe I'm just on crack, but since the original reconstructions of
_Baryonyx_, the arms of spinosaurs just keep getting shorter and stouter,
and less like a bear's arm. Perhaps Dr. Holtz, purveyor of hard data of
vertebrate macropredation, might be able to enlighten us.
        C) In any case, I'm not sure we should try to explain the robust
forlimbs as adaptations for a *piscivorous* function, since such a lifestyle
is not necessarily indicated as ancestral for the hypothesized
"torvosaurid"/spinosaurid clade (Spinosauroidea). Indeed, given what we know
of the rest of the skeleton of _Torvosaurus_, it seems more likely that
increasing prediliction for piscivory is only characteristic of the
spinosaurids. In such a model, the use of the robust forelimb for fishing
would be an *EX*aptation of the the original use (presumably terrestrial
macropredation).
        
>I can imagine a similar
>lifestyle for the Jurassic ancestors of Suchomimus--roaming around tearing
>apart nests or trees and using its long neck and snout to get to get at
>hidden prey (or even tearing apart carcasses).
        Hmm... an interesting suggestion. However, such a scenario is not
indicated by phylogenetic evidence (or, for that matter, any evidence that I
can see). The outgroups proposed by Sereno et al. are all large
macropredacious animals with macropredacious adaptions, and what we know of
spinosaurs seems consistant with that pattern, expect with a fisherman's
flavor (Old Bay?). Further, how big can an animal get and still live its
life this way? No, I don't want to hear about baby crocs eating bugs. :)
        
        Let's go arm some bears!
        Wagner
--------------------------------------------------------------------------------
     Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
 "Only those whose life is short can truly believe that love is forever"-Lorien