Re: Archaeopteryx, Sinornithosaurus, Rahonavis, Unenlagia...]

[Josh Smith <smithjb@sas.upenn.edu>]

Grant Harding wrote:
 Yet more questions about our favorite dinobirds. Was _Rahonavis_ any
less flightworthy than _Archaeopteryx_?  From what I've heard, it looks
like it's sort of intermediate in "flightworthiness" between
_Archaeopteryx_ and _Sinornithosaurus_ (or vice versa, depending on your
views on ground-up or trees-down).  Is this correct? Who has a more
advanced shoulder, _Sinornithosaurus_ or _Unenlagia_? In a recent
article on _Sinornithosaurus_ in the _Globe and Mail_, it also mentions
a "130-million-year-old bird that was so highly evolved by the late
Jurassic-early Cretaceous period [that Feduccia] believes there is no
way it could have evolved from a dinosaur."  What is this bird?
_Confuciusornis_?  It seems like the principal problem with all of this
(i.e., the Feduccia and Martin et al. groups' main support against a
dinosaurian origin of birds) was, is, and continues to be
_Confuciusornis_, at least where the "Yixian Fauna" is concerned.

Initially, it was discussed as substantially more derived than
_Archaeopteryx_, and although now it is considered to be perhaps a
chimera of sorts, _C. sanctus_ at least still possesses some characters
that simply are not basal avian features.  I think this is why they
("that group") harp on the age problem so much.  If we have critters
with edentulous beaks, true pygostyles and such coeval with
_Archaeopteryx_, this is a big problem.  _Rahonavis_ is pretty damn
basal, but I don't think it is less flightworthy than _Archaeopteryx_,
though it probably was less than _C. sanctus_, though there are enough
characteristics about the _Rahonavis_ that suggest a refugium that it
doesn't appear to be a problem.  It still all seems to hang on
_Confuciusornis_ and how it relates temporally to _Archaeopteryx_.  The
only way were are likely to shut these guys up is to find a
dromaeosaurid at Solnhofen...   I mean, face it, as cool as the Liaoning
taxa are, _Archaeopteryx_ still sits back on its wings and says, "hey
guys, you haven't found it yet--, its not over yet--I was already
here..."  It actually surprises me a little that the Feduccia crowd
harps on the Jurassic age so much, because _Archaeopteryx_ screams its
message even louder if the lower Yixian is ca. 125 Ma...