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Re: Obdurodon (was Re: Coronosaurus, new ceratopsid genus for Centrosaurus brinkmani)

Mickey Mortimer <mickey_mortimer111@msn.com> wrote:

> Preponderance?  We have Gansus and Hesperornithes showing aquatic 
> adaptations.  Yanornis sometimes ate fish (but so did Confuciusornis, and 
> it's not considered aquatic)

We also know that _Baryonyx_ and _Scipionyx_ ate fish.  These
non-avian theropods also lack any obvious aquatic adaptations.

> and Ichthyornis flew over the sea (but gulls and such are hardly aquatic).  
> Not showing aquatic adaptations are Archaeorynchus, Parahongshanornis, 
> Gargantuavis, Hongshanornis,
> Jianchangornis, Patagopteryx, Longicrusavis, Yixianornis, Apsaravis and 
> Schizooura.

You may be using the term more "aquatic" more rigidly than I am.  I'm
also using the term to include littoral/shore-dwelling birds.
Hongshanornithids (_Hongshanornis_, _Parahongshanornis_,
_Longicrusavis_) have features consistent with wading, particularly in
the hindlimbs and pedes.  _Archaeorhynchus_ has a beak reminiscent of
a spoonbill.  To me, the _Yanornis_ skull appears adapted for
fish-eating.  As you say, we know that _Yanornis_ ate fish; and based
on preserved remains of small teleosts close to the stomach,
_Jianchangopteryx_ may have eaten fish as well (on this basis, the
original description suggested it was piscivorous).  Plus we have more
crownward taxa such as _Gansus_ and the Hesperornithes, which like you
said were undoubtedly aquatic.  I would regard _Ichthyornis_ as
aquatic, especially if the reconstruction of this taxon a tern-like
bird is correct.

Of course, by no means all basal ornithuromorphs were aquatic; some
were certainly not (_Patagopteryx_, _Apsaravis_, etc).  But basal
Ornithuromorpha does seem crowded with putative aquatic/amphibious
birds, even if the criteria for identifying a particular bird as
"aquatic" can be vague.  By contrast, although there are putative
aquatic enantiornitheans, they are exceptional in this regard (among
Enantiornithes) and many more show highly refined perching abilities
suggesting they were specialized arborealists.