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RE: Jeholornis - long-tailed bird in today's Nature



Nicholas Gardner wrote:


> > That's right - a bird with a long dromaeosaurid-like tail, complete
> > with elongated and rod-like prezygapophyses and chevrons. _Jeholornis_
> > also has a T-shaped lacrimal; toothless upper jaw with a few teeth in 
> > the lower jaw (these are small and conical); short sternum; robust 
> > boomerang-like furcula; a forelimb to hindlimb ratio of about 1.2; 
> > three large and recurved unguals on the hand; a reversed hallux; 
> > pedal claws consistent with perching; and a large claw on the second 
> > toe "reminiscent of the situation of dromaeosaurids and troodontids".
>
> Curious and rather unusual.

Perhaps not so unusual.  Each basal bird shows a tendency to retain a unique
combination of "primitive" characters (primitive in the sense that they were
present in basal eumaniraptorans and lost in ornithothoracine birds).  To my
mind, these basal avialans represent individual experiments in "sorting out"
which eumaniraptoran characters should be kept (for feeding, for running
etc) and which should be jettisoned as their flight performance improved.

Zhou and Zhang describe the second toe of _Jeholornis_ this way: "The
hypertrophied second ungual is similar to that of _Archaeopteryx_ and
_Rahonavis_, and is also reminiscent of the situation of dromaeosaurids and
troodontids."  No explicit mention of a ferocious sickle-claw - which is not
present in _Archaeopteryx_ either, irrespective of whether _Archaeopteryx_
had a hyperextensible second pedal digit (as Gauthier and Paul advocate) or
not.  The figures show no sickle-claw for _Jeholornis_; and its presence
might be considered surprising in a seed-eater.

> > Last rites for BAND?
>
> Perhaps. :o)

I look forward to seeing this dromie-tailed flying bird explained away - as
either a chimera (as suggested for _Rahonavis_) or due to convergence (a la
_Caudipteryx_).  Be prepared for some creative writing.



Tim



------------------------------------------------------------------- 



Timothy J. Williams, Ph.D. 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 (office) 
       515 296 2687 (home) 
Fax:   515 294 9359