Re: Tarsitano's challenges

["Matthew Troutman" <m_troutman@hotmail.com>]

<<"The following morphological problems involving the theropod
ancestry of birds must be addressed by those who favor a
coelurosaurian ancestry or sister-group position for birds:
      (1) the absence of a siphonium and pneumatic quadrate in all
coelurosaurs;>>

Found in carcharodontosaurs, tyrannosaurs (coelurosaurs, not carnosaurs 
according to Tarsitano), and oviraptors.  (If memory serves, some recent 
troodontids and velociraptorines have been found with a quadrate-articular 
siphonium.)

      <<(2) the lack of clear evidence of a fenestra rotundum in 
coelurosaurs;>>

Tarsitano has his own definition of the fenestra pseudorotunda (which he 
calls the fenestra rotunda for a stupid reason), which not surprisingly 
excludes theropods.  The fenestra pseudorotunda appears to be at least a 
basal maniraptoran feature, if not a basal theropod feature.

      <<(3) nonavian tooth morphology in coelurosaurs;>>

By this he means teeth that are not triangular, peg-like, and have 
replacement pits, like that of _Archaeopteryx_ and crocodylomorphs.  
Juvenile theropods have birdlike teeth, sans the replacement pits.

      <<(4) reduced coracoids in all coelurosaurs;>>

A lie.  Coelurosaurs, even tyrannosaurs, have deep, birdlike coracoids with 
prominent biceps tubercles (acrocoracoids of birds) swept back caudally.

      <<(5) the presence of a massive and specialized pelvis and
hindlimbs that, biomechanically, seem to argue against the devlopment of 
flight;>>

Need we mention velociraptorines?

      <<(6) the presence of the middle temporal arch in coelurosaurs, but 
its absence in birds;>>

This is my favorite.  Using this criteria, all archosaurs, archosauromorphs, 
most neodiapsids (including lepidosaurmorphs) would be excluded from a 
relationship with birds.  Besides, _Archaeopteryx_, Confuciusornis_, and the 
enantiornithines have a middle temporal arch.

      <<(7) the presence of lateral basicranial sinus openings in
coelurosaurs, but their absence in birds.>>

Dubious.  This is based on the lateral concavity on the braincase of 
_Troodon_, which is only seen in some oviraptors, and therizinosaurs (I 
think).

The list above is basically a continuation of the birds-can't-be-dinosaurs 
camp's tactic of assuming difference in anatomy indicates non-relationship.  
Some examples, such as the propubic pelvis and the middle temporal arch, are 
just silly as they are being very myopic by not acknowledging that at some 
point in bird evolution, birds would have sister-groups with a propubic 
pelvis or a middle temporal arch (basically a postorbital-squamosal 
articulation).  Basically, because birds differ from theropods some details 
(these themselves are debateable), they cannot be related to them.  
Tarsitano and Hecht (1980), Hecht and Tarsitano (1982), Hecht (1985), 
Tarsitano (1985a,b), Tarsitano (1991), and Hecht and Hecht (1994) all show 
this argument.

Difference does not indicate non-relationship.

Matt Troutman
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