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Re: Qld Museum to unveil Australia's biggest dinosaur bones



Mike Taylor  wrote:

... but the news reports of this beast say that the femur is 1.8m and
the humerus "only" 1.5m, which is rather different from the
proportions expected in a brachiosaurid, so I am pretty confident that
the new Australian specimens are titanosaurians, i.e. members of the
clade (_Saltasaurus_ not _Brachiosaurus_).

Like a lot of situations, this depends upon the exact definition of Titanosauria. (All this is nothing new to Mike, of course. ;-) )


The earliest definition of Titanosauria is that of Salgado et al. (1997), who give it a node-based definition based on _Andesaurus_. This was essentially followed by Wilson and Upchurch (2003), who use both _Andesaurus_ and _Saltasaurus_ to anchor this clade. The definition given by Mike (_Saltasaurus_ not _Brachiosaurus_) is stem-based, and is the one used by Upchurch et al. (2004). Other stem-based definitions also throw in _Euhelopus_ as a second external specifier. Given just how unstable _Euhelopus_ is in sauropod phylogeny, and how poorly known _Andesaurus_ is at the moment, the stem-based "(_Saltasaurus_ not _Brachiosaurus_)" is probably the most workable definition.

So these new sauropods might be a titanosaur under one definition, but not under another. Ditto for _Austrosaurus_.

Cheers

Tim

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