Re: HYPSILOPHODONT MONOPHYLY

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

Pete Buchholz wrote:

> Also, the authors seem to sink three very distinct species into one in 
> regard
> to Yandusaurus hongheensis, lumping "Yandusaurus" multidens and Agilisaurus
> louderbacki all into the same species with Y hongheensis....  In my opinion
> it's like sinking Camptosaurus and Parasaurolophus into Iguanodon...
>
> Discussion?  Anyone have opinions?

Carpenter (1994) presents a good case for regarding _Yandusaurus multidens_ 
as a young individual (and therefore a junior synonym) of _Yandusaurus 
hongheensis_.  Carpenter (1994) sets out the features which distinguish _Y. 
multidens_ from _hongheensis_ and, based upon ontogenetic changes observed 
in a growth series of _Dryosaurus altus_, claims that all the features that 
define _Y. multidens_ as a separate species are in fact hallmarks of an 
immature individual.  Aside from smaller body size, these features include: 
enlarged orbits; shorter muzzle; scapula longer than humerus; absence of a 
ridge on the ventral surface of the coracoid; and humerus narrower at the 
proximal end and exhibiting less curvature of the shaft (Carpenter, 1994).

As for the headless _Othnielia_...  I heard a very sad story about how the 
skull of _Othnielia_ was stolen ("head-hunted") before the specimen could be 
completely excavated.  The specimen was discovered and its location noted, 
but when a team returned to begin excavation, the skull had already been 
excavated (presumably by private collectors) and has never been seen again.  
Is this a true story?  If so, it has my blood boiling...


References

Carpenter, K. (1994).  Baby dinosaurs from the Upper Jurassic Morrison 
Formation of Dinosaur National Monument. p.288-297.  In: Carpenter, K., 
Hirsh, K.E., and Horner, J.R. (Eds.).  Dinosaur Eggs and Babies.  Cambridge 
Univ. Press, U.K.
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