RE: tiny-armed theropods

["Thomas R. Holtz, Jr." <tholtz@umd.edu>]

On Sat, October 15, 2011 11:51 pm, Anthony Docimo wrote:

  It would seem to me that, if the _Troodon_ tooth morphology matches two
> or more troodontid genera (I assume you meant genera), then you'd know
> which troodontid clade _Troodon_ belongs to (which, granted, it was
> probably already grouped in).

If and only if that the two or more taxa who share this morphology share
it as a synapomorphy, not as a convergence.

>
>  Is it possible for multiple genera to have identical teeth?

Abso-friggen-lutely.

> Even if
> they're 99% similar, surely that remaining 01% could be used to determine
> the closest relatives of the _Troodon_ type fossil tooth.

Here is the problem: two individuals of the same ontogenetic status in the
same population might not have teeth that are 99% identical in the same
tooth position. The same individual might have teeth in the same tooth
position but opposite sides that are not 100% mirror images. The same
individual might have teeth in that position that are not 99% identical
from one tooth eruption to the next.

Sorry if this messes up people's typological worldviews, but *variation*
is the great reality.

So the issue is whether the _Troodon formosus_ tooth type can confidently
fit into the variation of one, but only one, species of skeletal taxon.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661

Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA