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RE: Who says dromaeosaurs can't fly?



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Fam Jansma
>
> Hi all,
>
> Let we just once settle this debate about cladistics and
> neo-flightlessness,
> there is absolutely no way that cladistics and cladisticists can prove
> wether if it occured.

[snip]

> The only way that neoflightlessness can be proven, is when flight is
> regarded as a primitive characteristic in PAUP so that it can be seen from
> the generated tree which genera are the most advanced, or to say it
> different, which have retained the less of the flight adapted features in
> their skeleton.

Actually, no.  There are other ways it could be demonstrated (the term
"proven" is not acceptable in this context in scientific circles) by
cladistic analysis.

Part of your discussion suggests that the character "volancy" has to be one
of the ones evaluated in the analysis.  However, there is some merit to not
including a particular feature in an analysis in order to avoid circular
arguments (i.e., assuming what you are trying to prove).  You can run the
analysis without that particular attribute, then map the observed
distribution of that feature onto the most parsimonious tree(s).

For example, say that the most parsimonious distribution of characters shows
the following:
Archaeopteryx
        Rahonavis
        clade A
                Cryptovolans
                clade B
                        Deinonychosauria
                        Avialae
                                Confusciusornithidae
                                Ornithothoraces

(which, quite frankly, is a quite reasonable hypothesis and probably only a
couple steps removed from the "standard model").

We then map "volancy" on this distribution:
Archaeopteryx - flying
clade A
        Rahonavis - flying *
        clade B
                Cryptovolans - flying *
                clade C
                        Deinonychosauria - flightless
                        Avialae
                                Confusciusornithidae - flying
                                Ornithothoraces - flying

* For purposes of this example, we assume that flying ability is present in
Rahonavis and Cryptovolans.  As has been pointed out, though, such is not
the case, insofar as demonstration of flight ability requires biomechanical
studies not yet done.

Based on this, you would have strong evidence for secondarily flightless
deinonychosaurs *EVEN THOUGH* the character "flight" wasn't included.

Please let me know if I was less-than-clear here.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
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