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



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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