Fwd: Re: Eolambia and Pararhabodon (was Re: New issue of JVP 2001(2))

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

Jonathan Wagner requested that this was forwarded to the list...


> >This is a particularly interesting paper.  Jason Head shakes the
> hadrosaurid
> >family tree again, this time arguing that _Eolambia_ is not a
> lambeosaurine,
> >nor even the sister taxon to the Lambeosaurinae.
>     Jason is almost certainly correct in this, although I have not
> received
> my issue yet so I've only read the abstract from SVP awhile back.
>
> >Certain lambeosaurine characters described by
> >Kirkland in the postcranium actually have a wider distribution within the
> >Iguanodontia - like the distally expanded ischium and tall neural spines
> on
> >the caudals.
>     FINALLY! These features have been plesiomorphic for the group since
> the
> beginning... why has it taken over 100 million years for someone to say so?
> Just kidding, seriously, many of the older discussions of postcranial
> characters in hadrosaurs are based on a typological and uninformative
> taxonomic structure. We are in need of a comprehensive reexamination of the
> subject. Stay tuned, hadrosaur enthusiasts...
>
> >Head (2001) places _Eolambia_ closest to _Probactrosaurus_
> >(likewise considered as non-lambeosaurine).
>     In his abstract, Head was very tentative about this conclusion, as it
> was supported by a shortened parietal suture, which he considered possibly
> a
> symplesiomorphy. My own analysis suggests this is indeed ancestral for
> hadrosaurs. Sadly, I have not had the opportunity to examine the Eolambia
> material, and the photos available are not particularly illuminating.
>
> >Head (2001) is also inclined to scratch _Pararhabdodon_ from the
> >Lambeosaurinae (referred to this group by Casanovas et al., 1999).
>     YES, yesyesyesyes! Say it print, say it again... An other character
> suggesting other affinities are the caudally swept coronoid process. There
> are more, but I'll keep them under my hat, for now... ;)

[ I would add that, if Jason is correct, then Lambeosaurinae is limited to
_Parasaurolophus_, _Charonosaurus_, _Amurosaurus_, _Jaxartosaurus_,
_Barsboldia_, _Corythosaurus_, and _Hypacrosaurus_.  As such, all
lambeosaurines are either known to have prominent crests, or (if the crest
is not preserved) closely related to a form known to have a prominent
crest).  I'm not certain of the placement of _Nipponosaurus_. - TW]


> Mickey wrote:
> >However, Head does not explain the posteriorly expanded subnarial
> >premaxillary process
>     The illustrations suggest that this is no more the case in E.
> caroljonesa than in other non-hadrosaurid iguanodonts.
>
> >or robust humerus, also lambeosaurine synapomorphies
> >according to Kirkland.
>     Well, "robust" has yet to be properly quantified, but it appears to be
> plesiomorphic for the group..
>
> >Head does not address other hadrosaur characters listed by Kirkland-
> >elevation of the dorsal maxillary process that brings the antorbital
> >fenestra onto the dorsal maxillary surface;
>     Eolambia IS a hadrosaur (under some definitions). just not a
> HADROSAURID. SO there was no need to mention these.
>
> >No argument against the presence of a medial maxillary shelf was
> presented,
>     ... and no evidence of the structure has been offered... actually,
> this
> character is BADLY in need of review. I'm working on it.
>
> Jonathan R. Wagner
> 9617 Great Hills Trail #1414
> Austin, TX 78759


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