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Re: Archie skull pneumatics?



I wrote:

<<There is no real elongated prenarial premaxilla in either
oviraptorosaurs or *Erlikosaurus*; in nearly all taxa, the external naris
progresses to the rostral end of the premaxilla and is even closer to the
edge than it is in *Velociraptor*.>>

Nick Gardner (ratites637@hotmail.com) wrote:
 
<Are you sure?  I probably should have checked the figures before
seconding someone's comment.  Out of curiousity, could one argue that the
ventral  margin length of the premaxilla might be elongated relative the
ventral margin length of the maxilla?  Sounds like it's time for me to get
the ruler and the calculator out...>

  David rewrote his interpretation of this character to equate to the
relative size of the non-narial premaxilla. However, relative area of the
premaxilla to skull and position of the external nares, and the length of
the premaxilla to maxilla appear to be three separate components on
premaxillary shape. Birds have a large triangular premaxilla with a
distinct rostrum, expanded external nares, producing a large premaxillary
component to the ventral length of the skull. In *Erlikosaurus*, the
premaxilla is about as long as in *Velociraptor*, but the external nares
are rotated caudodorsally and pulled backward, so that the caudal margin
lies nearly to the same extent as the rostral antorbital fossa; similarly,
the premaxilla is large, but the external nares extend to the rostral
margin. In oviraptorosaurs, depending on the taxon. *Caudipteryx* has a
trapezoidal premaxilla with an extremely large external nares and long
length relative to maxillary length, and the rostrum inclines backwards
slightly, unlike *Erlikosaurus*; in oviraptorids, the premaxilla has a
large area relative to skull area, and the external nares are both
elevated and retracted, yet the external nares remain near the rostral end
of the premaxilla. The elongate rostrum of birds is incomparable, except
in *Archaeopteryx*, where the premaxillary length rostral to the external
nares make up more than 1/4 the ventral premaxillary length.

<Oops, I just caught this mistake I made.  I meant to say, "I know that 
*Shuvuuia* does have an incomplete postorbital bar".  I'm surprised no one
 else noticed that error.>

  I read it as *Shuvuuia* lacking the bar, so I see no problem.

<Adult tyrannosaurid teeth?  AFAIK, they were not present only in the
teeth of juveniles...>

  The juvenile nature of *Aublysodon* is still hypothetical, even though
it fits with some other ontogenetic series ... none of these are dental so
far.

  I also wrote:

<<*Epidendrosaurus* (not known in *Scansoriopteryx*)>>
 
<My claim was based off *E.*.  I had thought they were synonymized.>

  They have not been. There are still differences between the two
similarly-sized animals to account for, and if any were to be synonymized,
it would be into *Epidendrosaurus* on the basis of dating, which
_Naturwissenschaften_ states occured several weeks before the print
version was made available, on account of the online-publication. This
gives *Epidendrosaurus* priority, no matter what was said by the Dinosaur
Museum.  However, this depends on actual synonymy.

<"Dromaeosauroids"?>

  If Dromaeosauridae is the most recent ancestor of *Dromaeosaurus* and
*Velociraptor*, and Deinonychosauria is all taxa closer to *Dromaeosaurus*
than birds _or_ the most recent common ancestor of *Dromaeosaurus* and
*Saurornithoides,* then the clade equivalent to the definition of all taxa
closer to *Dromaeosaurus* than to *Saurornithoides* or birds needs a name
... which I offer could be used as "dromaeosauroids." This is meant to be
vernacular only.

<Is it indeed present in segnosaurs and troodontids?  I've never really
been sure, it looks like it, but I wasn't sure.>

  Yes, both groups have it, at least for as many teeth as I have
uncovered. An upcoming paper should clarify the similarities between the
various pinched-crown, leaf-like teeth of various dinosaurs.

<Are you sure, as Ji et al. 1998 describe it as having 22 caudal
vertebrae.>

  In both the type and paratype, as well as one referred specimen, there
is an incomplete gap in the series, which is filled by haemal arches.
Reconstructing the series has approximated 24 through 26, though I am
willing to be wrong.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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