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Re: A Clutter of Duckbills



In a message dated 95-10-26 12:25:40 EDT, swf@ElSegundoCA.ATTGIS.COM (Stan
Friesen) writes:

>A. all published cladograms of these species place them in a single
>monophyletic group.
>
>B. The vast majority of the differences in these species are in the
>crest, which is a intra-specific recognition structure.
>
>C. Recognition structure tend to vary widely between closely related
>species, and thus are of low taxonomic weight.  If recognition
>structures are the main differences between two forms it is best to
>place them in one genus.
>
>
>Therefore it is best to unite these species in a single genus.
>

Not bad. I'm not completely up on these forms yet (wait until I finish the
article on ornithopods for Gakken), but I recall there are postcranial
differences between _Hypacrosaurus_ and _Lambeosaurus_/_Corythosaurus_; and
the postcranial differences between _Lambeosaurus laticaudus_ and the other
species are striking. Meanwhile, check out Horner & Currie's article on
_Hypacrosaurus stebingeri_ concerning why they place the species into
_Hypacrosaurus_ versus _Lambeosaurus_. The paper is in DINOSAUR EGGS AND
BABIES (Cambridge U Press).

If you're going just by skull display structures, then you should also adopt
Peter Dodson's viewpoint that _[Eu]centrosaurus_ and _Styracosaurus_ are
congeneric. They are sympatric and differ solely in the configuration of the
epoccipital ornamentation.

G.O.