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Re: Pelecanimimus



>From: tholtz@geochange.er.usgs.gov
> > >>  3) place Pelecanimimus all by itself in a more derived
> > >>     group than Ornithomimosauria; which seems like excessive
> > >>     splitting to me.
> > 
> > I agree.  However, you do exactly that with your usage of "Alxasauridae"
> > below.  That name is based off of the single species Alxasaurus
> > elesitaiensis.
>
>You seem to be using a different definition of oversplitting.
>
>I base it on level of divergence represented, not strictly on
>size.  (Although I try to avoid monotypic taxa, that is not always
>possible - especially in a highly diverse group, or a group with
>a small number of outliers).
>

In this sense, I'm using "oversplitting" as what should be called
"redundant taxa".  There has been a move among most taxonomists to
eliminate names for groups which contain only one member.  For example, at
present there is only the one genus Alxasaurus in the Alxasauridae, so the
second word is redundant.  Other monotypic (single member) names floating
around the dinosaur world are Compsognathidae, Dryptosauridae, Coeluridae,
and Psittacosauridae.

The classic example are the terms associated with the primitive bird
Archaeopteryx.  Although only one (debatably two) species is known,
paleontoloists have invented the names Archaeopterygidae,
Archaeopterygiformes, and Saururae for the family, order, and subclass
(respectively) which contain only Archaeopteryx.  Ironically, many people
who still use the more traditional classification system say that the
disadvantage of cladistics is that it adds too many names!

Note, however, that I still think that monospecific genera are a useful
concept.
                                     

                                
Thomas R. Holtz, Jr.
Vertebrate Paleontologist in Exile
U.S. Geological Survey
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092

email:  tholtz@geochange.er.usgs.gov 
Phone:  703-648-5280
FAX:            703-648-5420