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RE: Just what is the correct digital formula for birds and other theropods, anyway?

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]On Behalf Of
> David Marjanovic
> Sent: Thursday, August 24, 2006 4:24 PM
> To: DML
> Subject: Re: Just what is the correct digital formula for birds and
> other theropods, anyway?
>
>
> > but the problem would then be trying to find digit V, as the structure
> > identified as such would be reinterpreted as IV. Something called "Element
> > X" which had an unknown function was observed as well,  perhaps that has
> > something to do with it.
>
> I think that's it. It _was_ interpreted as such in the 1930s to 1970s
> (judging from one big German textbook anyway), and that interpretation still
> makes sense.
>
Actually, the bigger issue with this is that one has to move away from Owenian 
19th Century, or even embryological 20th Century,
style definitions of homology. Our growing knowledge of the genetic, 
phylogenetic, embryological, and related processes by which
organisms are built are now showing that the same physical part of an organism 
(in this case, the autopodium) can  go through
several different "identity" assignments (identity as an autopodium; identity 
as serially arranged digits; identity as particular
morphological structures; etc.).

Sure, it sucks from the point of view of a set of hard and fast rules, but 
That's Life...

See various papers by Larsson, Wagner, Vargas, Fallon, et al., previously 
discussed on this list: recently at
http://dml.cmnh.org/2005May/msg00616.html, for instance.

                Thomas R. Holtz, Jr.
        Senior Lecturer, Vertebrate Paleontology
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
        Mailing Address:
                Building 237, Room 1117
                College Park, MD  20742

http://www.geol.umd.edu/~tholtz/
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796