Re: Re: Mongolian Strata

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

>2 questions:
>
>1)  What is the currently accepted definition of the Euhelopodidae, and 
>what does it contain?  Where does it lie in the dinosaur family tree.  
>After reading Macintosh's article in _The Dinosauria_, I was pretty well 
>convinced that the Euhelopodidae were an unnatural assemblage of Chinese 
>sauropods, all of which had developed parallel adaptations for feeding at 
>the tops of trees, containing:
>
>_Euhelopus_, a camarasaurid;
>_Omeisaurus_, a shunosaurid related to _Datousaurus_;
>and _Mamenchisaurus_, between the Shunosauridae and the Diplodocidae.
>
>Have any of these been re-united into a larger Euhelopodidae?

Paul Upchurch and others (including George Olzhevsky, actually, from whom I
first encountered the concept) have quite convincingly made a case for the
monophyly of the above taxa, but also include _Shunosaurus_ and possibly
_Nuerosaurus_.  See Upchurch's paper in the Philosophical Transactions of
the Royal Society from September 1995 for the diagnosis.   As it turns out,
_Omeisaurus_, _Euhelops_, and _Mamenchisaurus_ all lack features of the
Neosauropoda (brachiosaurids, camarasaurids, titanosauroids, and
diplodocoids), but share a variety of features independantly evolved in
Diplodocidae.  All the euhelopodids may share a tail club.

Following Upchurch's phylogeny, Euhelopodidae is the sister group to
Cetiosauridae + Neosauropoda, and the phylogeny for the best known
euhelopodids is _Shunosaurus_ + (_Omeisaurus_ + (_Euhelops_ +
_Mamenchisaurus_)).

>2)  What _is_ the big-nosed Mongolian iguanodontid?

Whatever Sergei Kurzanov and/or Dave Norman want to name it...

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661