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Re: Enantiornithes question



In a message dated 8/28/98 8:46:27 PM Eastern Daylight Time,
dannj@alphalink.com.au writes:

<< On a skeletal reconstruction of Sinornis there seems to be some indication
of wing claws. Would this be something in common with most Enantiornithes
(especially Early Cretaceous species), and if so, would they be prominant
enough to be visible? >>

A while ago I posted some references on investigations of wing claws in modern
birds (see Carpal claws in birds; 7/29/98 6:55:39 PM Eastern Daylight Time
Patrick.Norton@state.me.us).  I didn't mention it at the time, but the authors
(particularly Fisher) noted that with very few exceptions, the carpal claws of
modern birds are hidden by wing feathers.  Illustrations of those claws show
them as greatly reduced, almost vestigial in appearance.  What is not hidden
by the feathers in some birds, and what are often mistaken for wing claws, are
bony "spurs" on the carpus that are often used as weapons.

If I'm reading recent works correctly (for example, see Chatterjee, The rise
of birds; 1997), modern birds are included within the monophyletic group
called Pygostylia which includes Enantiornithes and other birds possessing
(among other things) a fused carpometacarpus.  It seems reasonable to me that
the reduction or loss of carpal claws--such as seen in modern birds--is
related to the evolution of the carpometacarpus.  To cut a long response
short, my bet is that--to the extent Enantiornithes possessed carpal
claws--they were reduced in size and function and hidden by feathers.

The presence of a propatagia should also be considered in your Enantiornithes
reconstruction (although if your work is limited to skeletal elements, this
won't be relevant).  For a number of reasons, a fused carpometacarpus makes
little sense without the controlling musculature of the propatagia; and the
presence or absence of a propatagia would make a big difference in how the
animal looked. 

Pat Norton