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DROMAEOSAURS AND ARCHAEOPTERYX



DinosØMP wrote:
<<Does birds come from Archaeopteryx or late evolved small Dromaeosaurids, 
 like Velociraptor?!?>>

I, at one time, thought that Archaeopteryx and Dromaeosaurids formed an
exclusive clade and that _Archaeopteryx_ was ancestoral to dromaeosaurs.  In
light of the newly discovered theropod _Unenlagia_, it seems that that view
is incorrect for three reasons associated with the hips.

1) CRANIAL PROJECTION OF THE PUBIC BOOT: is a primitive character throughout
Tetanurae, but is subsequently lost in _Unenlagia_, _Archaeopetryx_, and all
other birds, as well as _Adasaurus_, the flying raptor, and "Linsterosaurus".
 The cranial projection is still present in dromaeosaurids and (surprisingly)
Alvarezsaurids (well, _Patagonykus_ at least).

2) PROXIMODORSAL PROCESS OF THE ISCHIUM: is a small knob on the caudodorsal
surface of the illium near the suture with the ischium and is a derived
character uniting _Unenlagia_, _Archaeopteryx, and all other birds.  I am
unsure of its presence in the flying raptor or "Linsterosaurus", and it is
probably not in _Adasaurus_.  It is completely absent in dromaeosaurs and
alvarezsaurids.

3) DISTAL PLACEMENT OF THE OBTURATOR PROCESS: is found in _Archaeopteryx_ and
all other birds.  I am unaware of the condition in "Linsterosaurus" and the
flying raptor.  Only the proximal portion of the ischium is preserved in
_Patagonykus_, so it is unknown at this time if the obturator process is
distal or not (I suspect not).  The obturator process is proximal in
_Unenlagia_ and dromaeosaurs.

For these three reasons, I believe that _Archaeopteryx_ is closer to modern
birds than dromaeosaurs.  I am not saying however, that dromaeosaurs didn't
evolve from a tree-living 'flying' ancestor, I am sure they did, juts that
that ancestor is more 'primitive' than _Archaeopteryx_.

These are also some reason why I believe Alvarezsaurids are less birdy than
they are made out to be.

Conclusions: 
1) The sickle clawed foot is almost certainly primitive for the clade uniting
_Dromaeosaurus_ and _Corvus, and perhaps Maniraptoriformes as well since it
appears in Troodontids, Dromaeosaurs, "Linsterosaurus", the flying raptor,
_Adasaurus_ and _Archaeopteryx_.
2) _Archaeopteryx_ is the outgroup to all other birds, with _Unenlagia_ and
Dromaeosauridae as successive outgroups.  
The flying raptor, "Linsterosaurus", and _Adasaurus_ fall somewhere in
between Dromaeosauridae and _Archaeopteryx_.  
3) _Adasaurus_ IS NOT another species of _Dromaeosaurus_.

Thank you for your time, and be thankful I didn't use any big words like
postcrania this time :-)

Peter Buchholz
Tetanurae@aol.com

Ya Ya! You best keep walkin' 'fya know what's good fo' ya!