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Re: Daanosaurus revisited



> Date: Thu, 29 Sep 2005 08:24:10 -0700 (PDT)
> From: Jay <sappororaptor@yahoo.com>
> 
> In other words, Bellusaurinae if you were a sauropod worker in East Asia.
> 
> Once we get mature specimens, they should be correctly called
> Euhelopodidae....

Not necessarily.  The name Euhelopodidae has been used for the clade
of Chinese sauropods (_Euhelopus_, _Mamenchisaurus_, _Omeisaurus_ and
_Shunosaurus_) recovered by Upchurch's (1995, 1998) analyses.  But
that group has been found paraphyletic by Wilson and Sereno 1998, in
which _Euhelopus_ was recovered as the sister taxon to Titanosauria,
motivating W&S to name the clade Somphospondyli = (Saltasaurus not
Brachiosaurus) which unites _Euhelopus_ and Titanosauria.  Wilson 2002
recovered a similar phylogeny, with _Euhelopus_ closer to titanosaurs
than to brachiosaurs, and the other Chinese taxa much more basal.  If
these topologies are correct, we surely can't use "Euhelopodidae" to
designate the basal Chinese clade.

In any case, the name Mamenchisauridae is older than Euhelopodidae, so
if we're going go defining a Chinese sauropod clade, that seems the
obvious candidate to use.  In Wilson 2002, _Omeisaurus_ and
_Mamenchisaurus_ together form a clade, the outgroup to (_Jobaria_ +
Neosauropoda), so you _could_ define something like Mamenchisauridae =
(_Mamenchisaurus_ + _Omeisaurus_).

However, Upchurch et al. 2004 recovered _Euhelopus_ as sister group to
Neosauropoda, _Mamenchisaurus_ just outside the (_E._+Neo) clade, an
_Omeisaurus_-_Tehuelchisaurus_ clade outside that, and _Shunosaurus_
much more basal.  So beware -- the definition above would amount to
nearly all of Eusauropoda under that topology.  Not only that, but
species-level taxonomy of both _Mamenchisaurus_ and _Omeisaurus_ is so
screwed up that some _M._ species may really be _O._ and vice versa,
so basing a clade on either is asking for trouble.

In conclusion, it's probably better just to say "Chinese sauropods" if
that's what you mean.  The evolutionary relationships of those babies
have been recovered in so many different forms that all bets are off
in terms of rigorous phylogenetic taxonomy.

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor  <mike@miketaylor.org.uk>  http://www.miketaylor.org.uk
)_v__/\  "Hui'chaa!" -- Gladiator in Quake II.