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Re: Defining clades like a REAL man (Was: New PaleoBios pa

Mike Taylor wrote:

Right, so where does that leave us with respect to the Chinese
sauropods?  The answer is, _nowhere_, because there is not one single
relationship between the Big Four (_Mamenchisaurus_, _Omeisaurus_,
_Euhelopus_ and _Shunosaurus_) that is consistently recovered by
multiple analyses.  [snip] In conclusion, you can't pick a well-resolved
representative of the group you want because (A) there isn't one, and
(B) "the group" might not exist anyway.

I agree, 100%. That a clade is well-supported should be a prerequisite for erecting a definition for that clade. However, a clade that is well-supported in 1990 may be dust by 2006. Things change - which is exactly what you were saying. I just don't think that well supported clades are necessarily immune to drastic shifts in topology, and definitions should perhaps take this into account. The Diplodocoidea looks pretty darn good in this respect; but who knows what tomorrow might bring? (Having said that, I don't think Diplodocoidea or Diplodocidae will cause any heartburn.)

I think the honest
thing to do is just hang back and not propose clades for the Chinese

For sure!

 Now Salgado et al. _might_ have been
right about the paraphyly/polyphyly of Brachiosauridae, and indeed of
the genus _Brachiosaurus_.

I won't dispute that _Brachiosaurus_ (_altithorax_ + _brancai_) and _Sauroposeidon_ form a clade to the exclusion of other sauropods. However, time will tell if these form a unique clade with other basal titanosauriforms, like _Pelorosaurus_ or _Atlasaurus_.