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Re: Family Nemegtosauridae



In a message dated 4/9/99 7:56:20 PM EST, A.Yates@zoo.latrobe.edu.au writes:

<<  I think
 that the bifid-spined Mamenchisaurus is still better placed with the
 strikingly similar but single-spined Omeisaurus >>

I was under the impression that Omeisaurus had bifid neural spines, but I 
went back to check and sure enough, they're still single. Mamenchisaurus is 
so obviously closely related to Omeisaurus that must indeed have acquired its 
bifid neural spines--not many of which are bifid, and those that are, are 
quite shallowly bifid, more like "deeply grooved"--independently. By the way, 
it's good that I checked, because I had been finding it difficult to place 
the euhelopodid/mamenchisaurid clade in my sauropod phylogeny, but now it 
fits right in below Camarasauridae and above Brachiosauridae + Titanosauria.

If you line up the sauropod families along the bifid-neural-spines 
morphocline, they also line up along the move-back-the-nares morphocline (for 
want of better names) and the elongation-of-cervical-ribs morphocline (which 
reverses in Diplodocidae/Dicraeosauridae).