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Re: Spinosaurus redescribed as giant semiaquatic theropod

dale mcinnes <wdm1949@hotmail.com> wrote:

> Didn't one spinosaurid specimen have the remains of an iquanodont inside its
> rib cage ?? A vertebra or 2 ?? Crocs are piscivorous also but still take
> terrestrial prey. But I am inclined to agree that spinosaurs were probably
> more piscivorous than crocs even. Who knows ..

Yes, we can only go where the evidence leads us.  The _Baryonyx_
holotype was found with remains of a small ornithopod as well as a
fish (_Scheenstia_ - formerly _Lepidotes_) as stomach contents.  The
tooth of another spinosaurid was found embedded in a pterosaur
vertebra, which suggests that pterosaurs were also part of the
spinosaur diet - though (as with the other food items) it's not known
if it was scavenged or predated.  Other non-avian theropods have been
found with fish as stomach contents (_Scipionyx_, _Microraptor_), as
well as a number of Cretaceous avialans (including _Confuciusornis_).

Based on their craniodental specializations, spinosaurids were likely
to have been predominantly piscivorous.  The postcranial skeletons of
like _Baryonyx_ and _Suchomimus_  lack any obvious specializations for
a semiaquatic or aquatic mode of life.  _Spinosaurus_ is different
(and more derived) in this respect.

The obvious hypothesis is that spinosaurids ate fish as part of their
diets, and that the lineage leading to _Spinosaurus_ began to spend
more time in the water targeting aquatic prey, and thereby over time
became more specialized for a semiaquatic lifestyle.  It may be that
the Kem Kem river system was particularly rich in large (and perhaps
not particuarly fast) fishes and sharks, which promoted this
specialization.  We just don't know whether _Spinosaurus_ had close
relatives (including descendents?) that took things further and became
fully aquatic.

I like Luis Rey's depiction of _Spinosaurus_ on the shore.  Like him,
I'm skeptical of _Spinosaurus_ (or any theropod) being capable of
quadrupedal walking on land.


But I'd be quite happy to see the future _Spinosaurus_ monograph
refute this interpretation, and establish _Spinosaurus_ as a viable
terrestrial quadruped when it ventured on to terra firma.