[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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
> > can't say more than "stay tuned"), specifically for the part that is
> > on
> Hmm.  While the idea of avian oviraptorids is intriguing, even
> characters don't turn the tide in my cladograms when combined with the
> evidence that dromaeosaurs (or alternatively alvarezsaurids and
> are closest to birds.  The characters in support of Elzanowski's
> don't hold up well when basal oviraptorosaurs and pygostylians are
> 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
> lacks a rod-like jugal.  Thus, parallel development may be a better
> explanation than common ancestry.

I didn't know these characters and haven't used them in my article. There
are quite few characters at all in it.

> 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....

?!?Oviraptorosaurs come out as Enantiornithes?!?

> > The pneumatization of the quadrates is an
> > extremely rare phenomenon in the dinosaurs (and not very extensive when
> > 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
> > with the braincase wall.
> Confuciusornis and Caudipteryx also lack pneumatic quadrates, so that may
> developed in parallel too.

Or _C_ and _C_ have reversed this state, or only immature specimens have
been examined... anyway, the joke is, I haven't seen any of the fossils I
write of in the paper, I have relied on the primary literature. The only
exception is one of the best _Confuciusornis_ specimens in the world (in the
Natural History Museum of Vienna), but all I've seen there is that it's
diapsid, and that's nothing new.

> > Pygostyles are now known in pygostylians, *Nomingia*, and arguably (not
> well
> > fused etc.) in *Caudipteryx* and *Protarchaeopteryx*. *Archaeopteryx*
> > not have one. Big question: Are any alvarezsaurid tail ends known???
> Caudipteryx lacks a pygostyle.  The distal caudals of Protarchaeopteryx
> unknown.

A few blunders on my part. The tail end of _P_ has still not been prepared
AFAIK, the only notable feature known so far is that its tail is terribly
short. For _Caudipteryx_, however, the best photo I have shows (at 4-fold
magnification) that the last few caudals look nearly like fused, are quite
featureless, and the tail tip is quite rounded. The print of this photo is
too coarse §$&% for more exact statements.
        How mature is this specimen?

Jennifer Ackerman: Dinosaurs Take Wing, National Geographic 194(1) (July
1998), 74 -- 99 (photo on p. 87)

> 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.

Of course. AFAIK, the difference between these 2 types is a gradual one:
more and smaller vertebrae are fused in the latter.
        Is it possible that the pygostyle was prone to fall off after death,
like the furcula? And I forgot to ask, are any oviraptorosaurian tail ends
other than those of _Caudipteryx_ and _Nomingia_ known?