Re: Yixian Dating Again

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

Jaime Headden replied to David Marjanovic-

> > <Would say nothing either way, if *Aristosuchus* and/or that pelvis from
> > Santana is compsognathid, too.>
> >
> >   Both appear to correlate very well to *Compsognathus*. *Scipionyx*
> > seems
> > similar and/or transitional between *Compsognathus* and *Ornitholestes*
> > in
> > quality, and *Sinosauropteryx*, despite the third specimen, looks like
> > it
> > si compsognathid in the broadest sense. It is notable that a
> > plesiomorphy
> > does not always mean it is more basal than the Comp + birds node, but
> > that
> > it is just more primitive; it may _be_ more basal, but not neccessarily

I agree Aristosuchus and the Santana specimen are much more like
Compsognathus than Sinosauropteryx is, so are more likely to be true
compsognathids.  I would say Sinosauropteryx is more basal than
compsognathids, Scipionyx is somewhere around that area of the cladogram,
but Ornitholestes is more derived than any of them.  But this whole mess
(and Proceratosaurus, Coelurus, Nwqebasaurus, Nedcolbertia and
Santanaraptor) is not well understood phylogenetically at this time.

David Marjanovic wrote-

> Would you say the teeth from Guimarota, not to mention the MJ ones from
> England, look like known troodontids? (I can't tell.)>

There are five supposedly paravian-like teeth illustrated by Evans and
Milner (1994) in their figure 18.7.
B is similar in shape to troodontid dentary teeth, being low and extremely
recurved, with only eleven denticles on the posterior carina.  However, the
denticles are not hokked apically.  Anterior serrations start halfway up the
tooth (DSDI 1.17).
C resembles Richardoestesia upon first glance, being slightly convex
posteriorly with very flat rectangular denticles (DSDI 1.07).  I have not
heard this suggested before, and it could very well be wrong, but that's
what it looks like to me.
D/E resembles a velociraptorine tooth in shape (elongate, very curved),
though the posterior serrations are not hooked.  There are no anterior
serrations to judge DSDI with.  It's serrations resemble B.
F is labeled a possible troodontid tooth, but doesn't resemble one at all in
my opinion.  It's elongate, with very low rounded denticles, the anterior
ones limited to the distal half.  It has a very high DSDI of 1.71,
comparable to only Ricardoestesia or velociraptorines.  The serration shape
resembles the former more.
G is said to be possibly allied with C, but the serration morphology clearly
matches B and D more.  It is intermediate in shape between B and D too,
having fourteen serrations posteriorly, and seven anteriorly at the tip,
though more were certainly worn off on each carina.  The DSDI is 1.4.

John Maynard wrote-

> i am confused. are you saying that you believe that sinornithosaurus and
> microraptor were avialans or eumaniraptorans? may be just my reading level
> that caused the confusion...

As Tim Williams explained, Avialae is a group within Eumaniraptora.
Eumaniraptora is Deinonychosauria + Avialae by definition.  I believe
Sinornithosaurus and especially Microraptor are probably basal avialans, but
most others think they are basal deinonychosaurs.  My statement was simply
indicating that I was not being biased when assigning taxa to higher clades,
because I was comparing them to the broader clade Eumaniraptora (that
everyone agrees they belong to), rather than narrowing it down to Avialae
(which is a minority opinion held by me).

> I believe that sinosauropteryx should be put in
> its own family, sinosauropterygidae and in a superfamily with the
> compsognathids.How many fingers did sinosauropteyx have? was it
> like ostram said compsognathus was and have 2, or is greg s paul right and
> it have 3, i dont have a good pic of the fossils to look at myself.

Sinosauropterygidae was created by Ji and Ji (1996), along with
Sinosauropterygiformes, in their horrible original description of the genus.
If all they include is Sinosauropteryx though, they are simply redundant.
Sinosauropteryx has three fingers (Currie and Chen, 2001), as is
hypothesized for Compsognathus (Gauthier and Gishlick, 2000).  Rauhut (2000)
thinks Compsognathus may have had four metacarpals, but I like Gauthier and
Gishlick's hypothesis better.

Mickey Mortimer