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Re: Screaming dromaeosaur biplane killers of the air



Jaime Headden wrote-

>   The statement should be that Sereno has presented a lot of data that
> supports *Iberomesornis* as a basal enantiornithine, but both Chiappe and
> Sanz have detailed some parts of the discussion of avian evolution in
> regards to *Iberomesornis* as having features of enantiornithines, and
> higher birds, leading them to suspect two alternate phylogenies, which I
> consider to be demonstrative of a little more doubt than "is actually one
> of the best known enantiornithines"; these phylogenies have
> *Iberomesornis* as either basal to the enant/ornithurine and as the basal
> ornithothoracine (thout by definition, it would be the sister group to the
> Ornithothoraces).

Actually, though before 2000 Iberomesornis was considered basal to the
enantiornithine-ornithuromorph split by Chiappe, he now (2001, 2002)
believes it is an enantiornithine.  Similarly, Sanz et al. (2002) now place
Iberomesornis in the Enantiornithines.  Regardless of the likely paraphyly
of enantiornithines as currently conceived, the characters used by Sanz
(1988, 1995) and Chiappe (1995) to place Iberomesornis below their level
have been nicely eliminated by Sereno (2000).
- The posterior cervicals of enantiornithines (eg. Eoalulavis, Catalan
nestling) are also amphicoelous.
- Prominent hypapophyses are present on the last cervical and the first
three dorsals.
- There are eight, not five sacrals.
- The scapulacoracoid articulation is not preserved.
- The transverse groove across the humeral head is not definitely present,
but is variable in enantiornithines anyway.
- The radial condyle is not preserved, and the ulnar condyle seems to round
on to the anterior side of the humerus.
- Pelvic fusion is variable in enantiornithines, and partially developed in
Iberomesornis.
- The proximal tarsals are completely fused to the tibia.
- There are no free distal tarsals.
Thus, the "alternate hypothesis" of placing Iberomesornis basal to classic
enants like Sinornis, Eoalulavis and Concornis is effectively dead.

Mickey Mortimer