Re: tyrannosaurids

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>> Nanotyrannus lancensis (Gilmore 1946)   late Maastrichtian, western North
>> America
>>         (?= juvenile T. rex?)
>>
>Tom:
>        I was pretty convinced that this individual was an adult. Why then
>the doubts about the validity of this taxon?

I myself haven't seen the actual specimen to vouch for its ontogenetic age.
Bakker et al. stated that most of the cranial sutures are fused,
suggesting a relatively advanced growth stage.  However, Carpenter (1992)
failed to find any unique characters in this specimen that are not found in
Tyrannosaurus, and suggested that it may just be a growth stage.  Either
sounds reasonable to me.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.