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At 10:11 PM 10/13/98 -0400, Larry Febo wrote:
>Monday the 12th, Dr. Holtz wrote (in response to Louis Rey):
>>To be fair to Ruben, he *explicitly* stated that he did not consider
>>_Megalancosaurus_ a bird ancestor of any sort. However, he did say >that
>>shouldn't dismiss information from it (specifically, his interpretation of
>>it as a glider) as a model for some hypothetical stage in avian origins
>>(following the Bock scenario-driven hypothesis of bird flight origins).
>Who is "Bock", and what was his scenario? (Like I said before, I`m a bit
>behind the times.). Thanx!
If you are "behind the times", then you should remember Bock, since he is
hardly a new name to evolutionary theory or debates on the origin of birds.
Ornithologist Walter Bock (Columbia Univ.) has been one of the main active
proponents of "scenario-driven" reconstructions of life's history, including
the origin of birds. To put it simply, you a) develop a scenario of a
sequence of changes in a lineage (from an ancestral condition to the
ancient), including a series of steps along the way, all of which have to be
"fit"; b) where possible, find modern analogs for each of the steps along
the way for comparative purposes; c) find a series of fossil forms *in the
proper stratigraphic order* that serve for each of the potential steps.
Bock's 1965 paper (The role of adaptive mechanisms in the origin of higher
levels of organization. Systematic Zoology 14: 272-287) discussed this in
relation to bird origins.
The Feduccia-crowd are openly Bock-ian (check out either Feduccia's 1980
_The Age of Birds_ and 1996 _The Origin and Evolution of Birds_ for
discussion), and I think that you can see several elements in the "debate"
related to the above: the obsession with finding all the players in the
proper stratigraphic order, the a priori assumption that birds were
*necessarily* arboreal gliders before they were birds, and (in the case I
mentioned previously) the plea to consider _Megalancosaurus_ as an important
analog to a particular stage in bird origins, even if it is recognized as
not a close relative to birds (nor particularly similar in postcranial
Other Bock papers of interest include:
Bock, W.J. 1985. The arboreal theory for the origin of birds. pp. 199-207.
IN Hecht, M.K., J.H. Ostrom, G. Viohl & P. Wellnhofer (eds.) The Beginnings
of Birds: Proceedings of the International _Archaeopteryx_ Conference 1984.
Bock, W.J. 1986. The arboreal origin of avian flight. pp. 57-72. IN Padian,
K. (ed.) The Origin of Birds and the Evolution of Flight. California
Academy of Sciences, Memoir 8.
Hope this helps.
Thomas R. Holtz, Jr.
Vertebrate Paleontologist Webpage: http://www.geol.umd.edu
Dept. of Geology Email:email@example.com
University of Maryland Phone:301-405-4084
College Park, MD 20742 Fax: 301-314-9661