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Re: Mei example
David Marjanovic wrote-
> > Archaeopteryx is closer to birds than oviraptorosaurs are because it
> > - elongate distal caudal vertebrae.
> > Lacking in short-tailed birds; also present in Ornitholestes and
> > Alvarezsaurus.
> So... if short-tailed birds were shown to either form a single clade or to
> be closer to dromaeosaurs, scansoriopterygids or suchlike, or both, this
> character would disappear from this list.
Um, no. As long as we have the topology (s(s(l(l(l,pyg))))), where 's'
indicates a taxon with short vertebrae, 'l' a taxon with long vertebrae, and
'pyg' short-tailed birds, the character would remain on the list. So for
example, (ornithom(ovirap(archae(rahon(drom,pyg))))). This has both of the
conditions you list, but the character remains unambiguous.
> > - proximal caudal centra rectangular in transverse section.
> Where have you found such a character? In Makovicky's thesis?
Rauhut (2000), who cites the Eichstatt and Munich specimens.
> > - reduced number of caudals with transverse processes.
> > Lacking in dromaeosaurids and Sinornithoides.
> I've recently seen the skeleton of an adult ( = huge!) chicken several
> times. Its transverse processes continue unambiguously into the
> and take into account that the _proximal_ caudals, those that alone bear
> transverse processes in long-tailed birds, have ended up near the middle
> the sacrum!
> Of course this could be a reversal. In *Sinornis* the last two
> caudals seem to have no transverse processes... but the proximal part of
> pygostyle does have a shelf that looks like a few fused transverse
> processes. In general transverse processes seem to continue into the
> pygostyle when one is present, *Nomingia* and (IIRC) *Beipiaosaurus*
> excluded (whose pygostyles are quite short).
The incorporation of caudals into the sacrum is indeed a problem with this
character. Unfortunately, birds were lowering both dorsal and caudal
counts, so determining how many sacrals were originally caudals is
difficult. Then there's the issue of how many caudal vertebrae are in the
pygostyle, and if this number differs between pygostyles of different length
(eg. Confuciusornis vs. Hesperornis). These issues do combine to make the
> > - distal chevrons bifurcated anteriorly.
> Distal chevrons are lacking in short-tailed birds. (The chicken mentioned
> above doesn't even have any chevrons at all.)
True. Forgot to note that.
> > - low number of maxillary teeth.
> > Lacking in Aberratiodontus; also present in Scipionyx (ontogenetic?).
> I wonder how much this is related to size... and of course to snout
I doubt it's size related. The highest tooth counts are among fairly small
theropods (e.g. Pelecanimimus, Byronosaurus, Saurornithoides), not large
ones. Similarly, Yanornis has a low number of maxillary teeth, despite its
long snout. It could be related to maxillary length, but the latter isn't
included in my analysis yet (though I'm in the process of coding it).
> > - jugal process of palatine absent.
> > Also present in Shuvuuia, Erlikosaurus and Incisivosaurus.
> And unknown in just about any Cretaceous bird except *Gobipteryx* and
> *Hesperornis*, right?
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html