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Re: New papers (relevant to bird origins)



David Marjanovic wrote-

> Great! I'll take this as support for my own paper (sorry, at the moment I
> can't say more than "stay tuned"), specifically for the part that is based
> on

Hmm.  While the idea of avian oviraptorids is intriguing, even Elzanowski's
characters don't turn the tide in my cladograms when combined with the
evidence that dromaeosaurs (or alternatively alvarezsaurids and troodontids)
are closest to birds.  The characters in support of Elzanowski's hypothesis
don't hold up well when basal oviraptorosaurs and pygostylians are examined.
Elzanowski states "Most intriguing are four characters that are shared by
the oviraptorosaurs and the ornithurine birds but are absent in
Archaeopteryx."  These are: articular with lateral process, articular with
medial process, mandibular symphysis fused, jugal rod-shaped.
Confuciusornis has a slightly expanded medial process and an unexpanded
lateral process, and lacks a mandibular symphysis (Chiappe et al. 1999).
Caudipteryx and Microvenator also lack mandibular symphyses, and Caudipteryx
lacks a rod-like jugal.  Thus, parallel development may be a better
explanation than common ancestry.  A couple notable errors in the paper
include: segnosaurs (and ornithomimosaurs?) do have a mandibular joint;
oviraptorids have coronoids.  For those who are interested, Elzanowski
includes a data matrix and cladogram of the supported phylogeny.  The
topology is (other coelurosaurs (ornithomimosaurs + segnosaurs +
oviraptorosaurs + birds)).  Elzanowski supports troodontids also possibly
being in the latter group and thinks oviraptorosaurs may be closer to
pygostylians than other taxa.  Actually entering the corrected matrix into
PAUP gives the result: (Dromaeosauridae (Ornithomimosauria (Archaeopteryx
(Segnosauria (Hesperornis (Gobipteryx + Oviraptoridae +
Caenagnathidae)))))).  Quite interesting....

> The pneumatization of the quadrates is an
> extremely rare phenomenon in the dinosaurs (and not very extensive when it
> does occur), but is a familiar characteristic of birds. The oviraptorid
> quadrate also has another unusual characteristic: instead of having only
one
> articular facet, as it does in all dinosaurs, it has an additional contact
> with the braincase wall.

Confuciusornis and Caudipteryx also lack pneumatic quadrates, so that may be
developed in parallel too.  The double-headed quadrate is quite interesting
however.

> Pygostyles are now known in pygostylians, *Nomingia*, and arguably (not
well
> fused etc.) in *Caudipteryx* and *Protarchaeopteryx*. *Archaeopteryx* does
> not have one. Big question: Are any alvarezsaurid tail ends known???

Caudipteryx lacks a pygostyle.  The distal caudals of Protarchaeopteryx are
unknown.  At least one caudal series of Mononykus or Shuvuuia extends to the
seventh from last caudal or so.  If they have pygostyles, they're
Nomingia-type, not pygostylian-type.

Mickey Mortimer