Re: Sereno's (2005) new definitions

["Jaime A. Headden" <qilongia@yahoo.com>]

David Marjanovic (david.marjanovic@gmx.at) wrote:

<We can be reasonably certain that the holotype of *Troodon formosus* belongs
to the clade commonly called Troodontidae. So I can't find anything to say
against anchoring Troodontidae on *Troodon*.

However, if (an entirely speculative example) someone would define, say,
"Troodontinae" as "everything closer to *Troodon* than to *Saurornithoides*",
then we _would_ have a problem because without the referred material it seems
not to be possible (at the moment) to determine exactly enough where within
Troodontidae *Troodon* belongs.>

  We are not looking at this in the right direction, as I tried to point out
before. Based on eponymy and Linnaean and ICZN useage, *Troodon formosus* will
always be in Troodontidae, as it by definition must always contain the type
genus and species. The principle of coordination, similarly, holds that it will
also be a "troodontine" or a "troodontoid" (at least if these names are coined
under the Linnaean system, as one could coin a "troodontoid" name under another
system it wouldn't be automatically a superfamily).

  The problem with *Troodon* is the problem of being able to relate it to other
taxa, and that the diagnostic comparisons to the type species must relate to
the tooth and the tooth alone. As with mammals, it may be possible to relate
this tooth further within a group of similar taxa, but so far, it is rather
unique, and most troodontids are Asian in fact, and may in fact be unique to
one another, pending a migration into North America of a select subgroup. This
is, of course, hypothetical.

  So, rather than run into this issue, Barsbold's method of recognizing the two
families may be ideal in some issues, or referring to *Troodon formosus* as
Troodontidae incertae sedis, which it appears to be. It's value in an analysis
is relatively limited, but as Mickey and others have shown, *Troodon* may be
relative, when assuming tooth placement, and shows up in the same part of the
tree. Large denticulation, however, is characteristic not of Troodontidae but
of a smaller clade within in, given the basal nondenticulate teeth in basal
taxa, or smaller denticles in *Sinornithoides*. I have some other proposals I
will be making that may help the issue for now....

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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