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Re: titanosaurs



In a message dated 12/3/02 12:51:04 AM Pacific Standard Time, 
qilongia@yahoo.com writes:

<< What whole series of bifid neural spines? Note that bifurcation of the
 neural spine occurs in more than one independant group of sauropods,
 including diplodocoids and camarasaurs >>

Who says camarasaurid and diplodocid bifid neural spines arose independently? 
I can think of a number of sauropod phylogenies in which diplodocid neural 
spines and camarasaurid neural spines might derive from a common ancestral 
form.

The point to remember is that if Opisthocoelicaudia is a titanosaur, it is 
the only one with a series of bifid neural spines. How odd to find this 
anomaly in the >same< genus that also features a caudal series that has 
exactly the opposite anatomy of titanosaur caudals. How odd to find bifid 
neural spines in a dinosaur from the same general region as a putatively 
independent group of sauropods (e.g., Euhelopus, Mamenchisaurus, Omeisaurus) 
known to have a series of bifid neural spines. So, if Opisthocoelicaudia 
acquired its bifid neural spines independently of all other titanosaurs and 
of all mamenchisaurs, just what was it about China/Mongolia that induced this 
particular anatomical curiosity in the sauropods that lived there? It seems 
quite reasonable to me that Opisthocoelicaudia derived from some kind of 
euhelopodid and acquired its suite of titanosaur characters convergently 
because it happened to have a lifestyle that matched that of some 
titanosaurs. Can't wait for a neck to be discovered for it: it could well 
have 16-17 vertebrae, like a euhelopodid descendant might be expected to have.