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Archaeopteryx and Parental Care




Just finished reading Carey and Adams' paper in the German journal
Archaeopteryx.  Many thanks to Jeff Hecht for providing me with a copy.

The fundamental premise is that the need to protect and sequester young led
to the development of long feathers on the forelimbs and the evolution of
arboreality.  There are a few problems with the paper - notably the authors'
lack of familiarity with theropod antomy, and their reliance on Feduccia in
their reconstructions of _Archaeopteryx_: apparently _Archaeopteryx_ has a
beak(!), and was an arboreal avian because of claw geometry alone.  The
emphasis on the avian beak as the "jack of all trades" of avian anatomy is
central to the paper, particularly its use in parental care.  A few
listmembers expressed concern that Carey and Adams may not recognize the
primitive purpose of the theropod forelimb (i.e. procuring prey), and (alas)
this is apparent in the paper.  

Carey and Adams are also on shaky ground when they outline the time-honored
"arboreal" vs "cursorial" dichotomy, since it is clear they are not at all
familiar with the latter in any of its versions.  I can't think of a single
cursorial model which posits a quadrupedal ancestor (maybe Nopcsa?), nor can
I envision why a terrestrial proto-avian would want "bat-like membranes"
(though the authors may be referring to incipient patagia to increase
surface area). 

The paper is mostly "just-so"-ing, but there are a lot of good ideas.
There's some interesting stuff on feather morphology in modern flightless
birds, particularly the differences between different secondarily flightless
species ("shaggy" vs pinnate, associated with solar shielding...?).  Carey
and Adams also provide an explanation for the mosaic anatomy of
_Archaeopteryx_ (enlarged feathers were developed for parental care and
solar shielding), which remind me of Tom Hopp's brooding hypothesis - though
I think Archie's mosaic anatomy can be explained much more plausibly (and
parsimoniously) by other hypotheses. 

Food for thought; although a few of Carey and Adams' ideas gave me
indigestion.



Tim


Reference

Carey, J.R. and Adams, J. (2001).  The predaptive role of parental care in
the evolution of avian flight.  Archaeopteryx 19: 97-108.



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

Timothy J. Williams 

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

Phone: 515 294 9233 
Fax:   515 294 3163