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Re: *Utahraptor* and Polyphyly of Recent Dromaeosaurids



I wrote:

<<1. fused interdental plates;>>

Mickey Mortimer (Mickey_Mortimer@email.msn.com) wrote:
 
<Present in Dromaeosaurus, Achillobator, Deinonychus,
Velociraptor and Bambiraptor, but not in Sinornithosaurus.>

  [Sinornithosaurus:] in the matrix. The paper does not mention
them, and the medial view of the dentary in the type (IVPP
V12811) does not show them, which is peculiar. But I need a good
photo of this. The photo by Luis Mazattenta on pg. 104 of Sloan,
1999 (_Nat. Geo. Mag._ 196, 5: 98-107) [probably the best thing
for this article is the photos] appears to suggest there are
distinct division perpendicular to the dorsal margin of the jaw,
but there are a few caudal fractures that continue in the
specimen beyond the jaw that suggest these need investigating.
They look like they're there, though. Irrelevant, however,
considering parsimony considers the group == { *Dromaeosaurus* +
*Deinonychus* } is still validated by this feature; as Xu et
al., suggest, *Sinornithosaurus* is outside Dromaeosauridae
using Currie's definition.

  The condition is present in a ton of avetheropods as well, but
this can also be considered convergent (see below under lateral
squamosal ridge for more discussion).
 
<<2. lateral frontal process turned at an angle to meet
postorbital;>>

<Present in Dromaeosaurus and to lesser degree in Velociraptor,
but Bambiraptor and Sinornithosaurus are similar to
troodontids.> 

  *Deinonychus* apparently has developed processes, but the
extreme condition in *Dromaeosaurus* appears to be
autapomorphic. I wouldn't call the processes in *Bambiraptor*
and *Sinornithosaurus* to be very laterally oriented, as you
note. Dromaeosauridae is still supported, and the value of this
character is probably inherent in the angle relative to the
narrowness of the frontals and the angle of the orbital rim to
the sagittal line. 

  angle of process to orbital rim (in degrees):
    *Velociraptor*: ........ 56
    *Deinonychus*: .........  9
    *Sinornithosaurus*: ....  9
    *Bambiraptor*: ......... 33
    *Dromaeosaurus*: ....... 3-(-192)
    *Saurornitholestes*: ... 19
  angle of orbital rim to frontal midline (in degrees):
    *Velociraptor*: ........ 17
    *Deinonychus*: ......... 60
    *Sinornithosaurus*: .... 33
    *Bambiraptor*: ......... 15
    *Dromaeosaurus*: ....... 88
    *Saurornitholestes*: ... 35

  For comparison, the values in *Saurornithoides mongoliensis*
are, relatively, 1 and 42.5 degrees (the frontal angles twice
from the sagittal line, so that the longest length of the
orbital rim is 42.5 degs from the sagittal angle (1 deg) and the
orbital rim turns 44.5 degs again for about a tenth the rim.
This is unlike the condition in "deinonychosaurs" (_sensu_
Padian et al., 1999). *Archaeopteryx* is 44 for the first value,
based on Paul's (1988: pg. 354) figure of the Solnhofen
specimen. The distoritive qualities of the skull in this taxon
make me cautious in rendering the cranium itself, but this value
is probably quite close to the true value.

  Note: above, in the values for *Dromaeosaurus,* the orbital
rims of the frontals are more or less parallel to the sagittal,
but one is wider rostrally than the other, acheiving a higher
(1) value than the other (-192); the mean is -196.5.

<<3. vertical posterior process of the articular posterior to
the retroarticular process;>>

<I'd like to see evidence of this in taxa besides Dromaeosaurus
and Bagaraatan.>

  Both *Bambiraptor* and *Velociraptor* bear a dorsally
ascending posterior "stylus" of the articular posterior to the
articular basin (see Burnham et al., 2000: pg. 3; and Barsbold
and Osmólska, 1999: pg. 211). In both, the process is low, but
still vertical to sub-vertical, and in the latter it is inclined
somewhat medially. I am unaware of the condition in the former,
but this should be elaborated upon in the forthcoming monograph,
when it is finished.

<<4. squamosal bears a lateral ridge from the postorbital to the
paroccipital process;>>

<Judging by my not-so-clear photocopies of Clark et al. (1994),
this seems to be present in Erlikosaurus.  It is present in
Dromaeosaurus, Deinonychus, Velociraptor and Bambiraptor, as
well as Archaeopteryx.  Allosaurus and Carnotaurus also show
this character.>

  It can be argued that the condition we note in allosaurus and
carnotaurus are 1) the plesiomorphic condition reversed in
coelurosaurs then reversed again in dromaeosaurs, or 2) are
convergent. Both entail three steps, so are equally
parsimonious. 
 
<<5. quadratojugal "T"-shaped, the posterior process about as
long as the anterior process;>>

<This is present in Dromaeosaurus, Deinonychus, Velociraptor,
Bambiraptor and Sinornithosaurus, but also in Erlikosaurus.>

  And a "conchoraptorine" oviraptorid, whose skull I have
illustrated for my site and is part of the travelling Russian
Dinosaur Exhibition. A very robust quadrate process. The
condition in *Erlikosaurus* may then support inclusion of this
character as part of Maniraptora, and excludes *Archaeopteryx*
and troodontids from consideration (or as reversals of the
maniraptoran condition). So you are right in pointing this out.

<<6. the prefrontal is fused with the lachrymal, forming a
"T"-shaped lachrymal (not analogous to the T-shaped lachrymal of
ornithomimids, whose prefrontal is separate);>>

<This can also be seen in oviraptorosaurs, troodontids and
confuciusornithids.  Dromaeosaurus, Deinonychus and probably
Sinornithosaurus have unfused prefrontals, while Velociraptor
and Bambiraptor show the advanced condition.>>

  The condition is the opposite in oviraptorids (the rostral
process is covered by the subnarial process of the premaxilla),
and the caudal process is an extension of the medial extension
on the cranial roof, so they are not analogous. Troodontids
seems to have semi-separate prefrontals and the posterior
process does not extend caudally as far as it does in
velociraptorines -- the prefrontal is actually quite small and
indistinct; the condition in troodontids is not the same as in
dromaeosaurids, as the orbital shelf extends laterally onto the
lachrymals and is confluent with the dorsal antorbital rim.
*Dromaeosaurus* does not possess complete lachrymals or
profrontals even, so the condition is very problematic. My boo
for using this as a dromaeosaurid character, but it seems
equivocal either way. 

<<7. form of the denticles of the teeth;>>

<Not sure what you mean here.  The velociraptorine tooth form is
known in most taxa, but notably lacking in Dromaeosaurus,
Achillobator and Utahraptor.>

  I clarified this in my response to Josh Smith. Troodontids and
dromaeosaurids.

<<8. dorsal vertebrae with pedunculate parapophyses;>>
 
<Not examined in most taxa, but also present in Patagonykus and
Mononykus.>

  Then synapomorphic for both groups, but unless you're arguing
monophyly of *Velociraptor* + *Mononykus*, this is not
autosynapomorphic of them, and is convergent under most recent
analyses. Besides, it's unknown in *Dromaeosaurus* anyway,
another boo on my part. Still, 5 out of 8 is not bad, with one 
equivocal character (fused interdentals).

<What?! Sinornithosaurus has a narrower jugal, if the element
questionably identified as jugal by Xu et al. is correctly
identified.>

  As I see it, it doesn't resemble any jugal I've seen, and
actually looks a lot like the rostral (palatine) processes of
the pterygoids in *Archaeopteryx*; plus, the element seems to be
a bit distorted in the photo mentioned above.

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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