RE: Hadrosaur nomenclature

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

> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Paleo_Mont
> Sent: Tuesday, October 16, 2001 1:48 PM
> To: Dinogeorge@aol.com; dinosaur@usc.edu
> Subject: Re: Hadrosaur nomenclature
>
>
> Ok...guess I need to do something here, again.
>
> >Maiasaura = Brachylophosaurus<
> >I admit I don't know much about hadrosaurs, so maybe this is old, but I
> haven't heard it before. What's the reasoning behind this
>
> >  Because the look similar. I'm not being smart. The Mor adult Maiasaura
> skull is crushed dorsal-ventrally. ROM has a new uncrushed skull
> that really
> really looks like Brachylophosaurus without that crest in the back.
>
> Arg... Hello not that similiar. That specimen is not that new. 93/94/95 or
> so when it was acutally found. Is also, the same speciman that
> has the skin
> impressions that show a "waddle" (loose skin under the neck).

"wattle".

However, differences do not equal non-relation.  I believe that Jon "Acolyte
of the Preisthood of Brett-Surman" Wagner is using a broad genus concept in
this context: that is, the species previously assigned to the separate
genera _Maiasaura_ and _Brachylophosaurus_ are all included in a single
genus (which, by priority, would be _Brachylophosaurus_).  Jon did similar
synonymizations in his poster presentation (i.e., _Anatotitan_ within
_Edmontosaurus_; _Prosaurolophus_ within _Saurolophus_; _Gryposaurus_ within
_Kritosaurus_; etc.).

There does not exist such a thing as a "genericometer" which can give
independant confirmation that two species or specimens differ at the "genus
level".  Thus inclusion or exclusion of a particular species from a genus
are matters of personal decision, although one hopes informed by information
on population and ontogenetic variation, distribution, phylogenetic
position, preservation, sexual dimorphism, and the like.

                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