Mickey Mortimer (Mickey_Mortimer111@msn.com) wrote:
<I'm not sure if the small fragment adhering to the pubic peduncle is
actually a part of the pubis. The main pubic piece seems to be in
anterior or posterior view, so does not help the situation. I also made a
skeletal reconstruction, which shows the pubis being barely propubic. It
seems in general we agree that segnosaurs were moving from something close
to a mesopubic condition to an opisthopubic one.>
Pubic peduncle morphology in two fairly avian style pelves but with
variant pubic orientation is identical; take *Archaeopteryx* and
*Velociraptor*, both of which have a slightly caudally-facing ventral
margin of this part of the ilium. The pubis, however, are apparently
oriented differently. The proximal pubes of two taxa with similarly facing
pubic peduncles, *Sinornithosaurus* and *Nomingia*, have mesopubic to
slightly-propubic conditioning, and that of *Archaeopteryx* may have been
mesopubic while that of *Velociraptor* was definately opisthopubic.
Ventral facing pubic peduncle in *Achillobator* (a recent publication with
a misspelling (the new *Citipati* paper) suggests that the intended name
may have been *Achillobataar*, but the english may have been rendered from
a different source than the typical mammal pubs, giving us the variant
"bator" spelling ... however, I digress) is comparative to the slightly
opisthopubic to mesopubic pelvis as I reconstruct it. The issue about
pubic peduncle orientation may be equivocal, especially in regard to
debate over *Archaeopteryx* orientation (not that kind!); similar
orientation of the pubic peduncle with variant pubic orientation suggests
the key feature is the proximal pubis, missing in *Beipiaosaurus* and
making the nature of the orientation a definate mystery.
<Well, there's always my 2000-2001 analyses, which included all the
characters Xu et al. did and much more, along with a lot more taxa.
Looking at the deinonychosaurian characters Xu et al. found in
Sinornithosaurus-
1. T-shaped lacrimal.
Very widespread, also being found in ornithomimosaurs, oviraptorosaurs,
Avimimus, troodontids, confuciusornithids and the Spanish nestling
enantiornithine for example.>
Uhm, *Avimimus*? What lachrymal? The refered cranium PIN 3907/3 is so
well fused and defined it is not possible to determine a condition as to a
posterior lachrymal, if present at all.
The theory that the posterior process is apomorphic of the bone itself
or is 1) neomorphic, or 2) a fusion of the prefrontal to the lachrymal is
not resolved yet, though fossils indicate a T-shaped lachrymal element (or
lachrymal+prefrontal elemental fusion) as a Maniraptora synapomorphy).
Yeah, this character's out, and does not assert a distinct non-relative
avialaean character.
Secondly, troodontids are deinonychosaurs by definition in some
analyses.
< 3. T-shaped quadratojugal
True, though also found in Erlikosaurus.>
This may be immaterial. The extent of a posterior process of the
lachrymal (the quadrate is transfered caudally from the junction of the
rostral and dorsal rami, resulting in an extension caudally of the
quadratojugal--quadrate contact) is present in a derived segnosaur, but
also three different oviraptorids (GI 100/32A [*"Oviraptor"
mongoliensis*], and two undescribed skulls, one of which is probably a new
species of *Citipati*). The structure may 1) be plesiomorphic to a
Eumaniraptora + Oviraptorosaur/Segnosaur clade, or 2) derived within the
group, and convergent. A derived skull of a segnosaur, three derived
skulls of oviraptorids (though Mickey disagrees with me on this point,
pers. comm.), the absence of the condition in a purported basal
oviraptorosaur (*Caudipteryx*) indicates a precedence of convergence. Only
*Sinornithosaurus* plus dromaeosaurids have the posterior and rostral rami
nearly in 180 degrees to one another, unlike other taxa, and this is
absent in other taxa including *Archaeopteryx* or birds. The condition in
*Unenlagia* and *Rahonavis*, both avialaeans, is unknown.
Presently, I'd say this character supports *Sinornithosaurus* as a
stem-dromaeosaurid (needs a name, and under current convention, the name
Dromaeosauroidea would seem applicable [*Dromaeosaurus* + oides {grk.,
form}, lit., the form of *Dromaeosaurus* and a means of providing a
non-Linnaean formate for suprageneric clade names while following a
convention of name-nesting:
-idae > idem (Lat.) the same, hence: those that are the same as [insert
taxon]
-inae > diminutive of idem (Lat.) ... see above.
-ini > diminutive of -inae > idem (Lat.) ... see above.
-oides > (apparently Grk.) form, shape of, hence: those with the form of
[insert taxon]
and so forth. Usage of suffixes as actual roots will better provide a
stable format for non-Linnaean formulations, and in fact reflects the need
to provide an etymology for what is essentially a new name. Provision of
suffices to represent ranks rely on the relative nature of ranks, which
are paradoxical in nature as they rely on the taxon name to define their
position.
<4. quadratojugal fenestra wide open
True for Velociraptor, but not Dromaeosaurus.>
I think we can all agree that *Dromaeosaurus* is a very well derived
taxon, especially in personal examination suggests the skull was more
rigid to provide a more powerful bite and jaw structure. This is reflected
in the shorter, wider snout, thicker teeth, more robust jaw, etc. Besides,
*Deinonychus* has a broad quadrate foramen [the quadratojugal foramen, as
I understand it, is the _rostral_ foramen as seen in some "hypsilophodont"
ornithischians].
<5. dorsal and ventral margins of dentary subparallel
As often as I've seen this character used, the condition in dromaeosaurs
doesn't look any different from other theropods to me.>
More likely to consider this as the lack of a mesial dorsoventral taper
in the dentary. This is dependant on how far the parallel is carried back
in the jaw, so a measure of relative depth to position in jaw
rostrocaudally in sequence would be a nice way to test this.
<6. Elongate distal chevrons and prezygopophyses
Also in Microraptor, which is even more bird-like (but still thought to
be a deinonychosaur by many).>
Yes, and for many other reasons, including the pes construction (an
apparent troodontid + dromaeosaurid synapomorphy, along with pedal digit
II features).
<Characters shared between Sinornithosaurus and birds, but not
dromaeosaurids- premaxillary body low;>
Seen in troodontids, ornithomimosaurs, blah blah. Probably related to
small premaxillae. Dromaosaurids proper are larger and may have
specialized to larger prey, plus they have larger premaxillary teeth and
hence need a deeper premaxillary corpus ... thus, dromaeosaurids proper
can have easily reversed this, and the feature can be considered as
irrelevant by reason of functional morphology and diet-related variation,
as well as a size-related feature (*whew*! breath ...)
<unserrated premaxillary teeth;>
Functional, irrelevant, and convergent with other taxa; perhaps diet
related.
<quadratojugal-squamosal contact absent;>
Also in dromaeosaurids, actually; and variable in some Maniraptora:
there are two oviraptorid skulls I can show that lack this condition.
<smaller angle between scapula and coracoid;>
As Paul shows, this may be related to loss of flight in the larger
deinonychosaurs. *Sinovenator* as a basal troodontid shows an "advanced"
shoulder. So hardly unequivocal.
<more transversely oriented distal coracoid;>
Same as above.
<more than three pairs of sternal ribs;>
Not exactly ... *Sinornithosaurus* doesn't have that much in the way of
sterna.
<boomerang-shaped furcula;>
Not in *Sinornithosaurus*; its is rather shallow in aspect when viewed
from the "top/rostral".
<metacarpus over 40% of femoral length;>
Similar to the coracoid and scapular features, and flight related, as
such ... equivocal.
<no anterior pubic foot;>
Not sure the slight flange in *Deinonychus* counts; *Velociraptor* lacks
this flange, has no projection, and neither does *Sinovenator.*
<proximodorsal ischial process;>
maybe related to locomotor performance, but this seems pertinent.
<mid-dorsal ischial process;>
er ... distodorsal ischial process, in coherence with the previous
terminology, I think, sounds better. However, this is not always present
in advanced forms and is of similar functional relevance, and may be more
equivocal as a result of it's variability.
<fibula <20% of tibia width.>
Size related.
<There are also several characters also found in more derived birds, but
not Archaeopteryx- three distal quadrate condyles;>
Ah, yes, a "lateral" process below the quadratojugal, seen in
oviraptorids as well.
<expanded manual phalanx II-1;>
In what manner is it expanded?
<no distinct posterior pubic foot.>
It's big, "hooked", makes the pubis look like a "J" (cf. posts by Pete
Buchholz a way back in the archives).
<I think it might be an enigmosaur, but Paul presents evidence it's an
archaeopterygid.>
Not sure ... the teeth are equivocal in nature and Rutger's support for
similarity to *Caudipteryx* is not viable as the teeth are distinctly
different, and the skull is so highly eroded and/or deformed as to limit
any examination apart from a generalized shape. But cool anyway ... limbs
are rather plesiomorphic, and it would seem to be either basal
maniraptoran, or quite avialian or avian in nature.
---
other features that support the Deinonychosauria and the close
association of *Sinornithosaurus* to Dromaeosauridae:
1. pedal phalanx II-2 with elongation of the ventral edge of the
proximal articular facet, providing the dorsal extension of the ungual
phalanx.
2. pedal phalanx II-3 ungual forms raptorial claw.
3. elongate posterior flanges of the metatarsals II and IV, converge or
nearly converge at the midlength.
I'm too lazy right now to look up the rest that Xu et al. support
outside of the the obvious plesiomorphies.
=====
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.
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