Re: Defunct genera and _Pekinosaurus galtoni_ (was Re: Suchomimus' forcula)

["Timothy Williams" <twilliams_alpha@hotmail.com>]

Dinogeorge wrote:

> << Zounds, dinosaur genera are being sunk faster than new ones are being
> named. >>
>
> No, it's just the lumpers having their turn.

In these cases I think the lumping is justified.  Well-represented dino 
species (_Allosaurus fragilis_, _Coelophysis bauri_, _Triceratops horridus_, 
to name a few) tend to show a lot of morphological variation within the 
species.  David Smith's morphometric analysis of _Allosaurus_ bones 
(published in a fairly recent JVP paper) showed this to be true for _A. 
fragilis_. Or, to put it another way, one _Allosaurus_ species showing a lot 
of variation was the most parsimonious way to explain the results of the 
analysis (as opposed to several co-existing _Allosaurus_ species showing 
little variation; _Saurophaganax/Allosaurus maximus_, though, does seem to 
be a valid and separate species from _A. fragilis_).  When you think about 
it, a happy and healthy dinosaur population ought to show a lot of 
phenotypic variability.

In the past, when I was looking at the descriptions of _Anasazisaurus_ and 
_Naashoboitosaurus_ (each based on a single skull) I remember struggling to 
discern exactly what was so different between these two genera and 
_Kritosaurus navajovius_.  According to the hadrosaur paper in the NMMNH 
volume, the difference appears to be minimal and explainable by 
morphological variation, or due simply to ontogeny (revealed by comparison 
with different growth stages of _Prosaurolophus_).

_Brachyceratops_ and _Monoclonius_ (for the Centrosaurinae) and 
_Maleevosaurus_ and _Nanotyrannus_ (for the Tyrannosauridae) are four more 
genera who have bit the dust, and to me their passing seems justified: the 
most parsimonious explanation appears to be that their "diagnostic" 
characters are juvenile/subadult traits.  This only becomes apparent after 
comparison with species for which growth series are known.

Still, if someone wants to sink one genus into another, I'm not going to 
accept it blindly.  I personally think _Cathetosaurus_ is quite possibly a 
valid genus (it has a few titanosauriform features not seen in 
_Camarasaurus_), and I have doubts about whether _Jurapteryx_ is a young 
_Archaeopteryx lithographica_.


Tim


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