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Remember the Alamosaurus (was RE: taxonomy is not stratigraphy)

Denver Fowler wrote:

Material assigned to the dustbin taxon 'Alamosaurus' may or may not represent a single genus or species.

Exactly so. _Alamosaurus_ has become the _Titanosaurus_ of North America. Every titanosaur bone from the Late Cretaceous of the SW United States has been referred to this genus, even though it appears that the sum total of _Alamosaurus_ material is incompatible with one species. This has been brought up in some recent papers. Let's hope the type material for _Alamosaurus sanjuanensis_ is diagnostic...

In fact, 'Alamosaurus' is probably a very bad choice for a biomarker since the holotype material bears no synapomorphies.

Oh dear. Looks like I spoke too soon. Nevetheless, the _Alamosaurus_ holotype material may show a unique combination of characters, even if autapomorphies are not present. But you're right: it's a terrible choice for biomarker. The jury's still out whether it's a valid taxon.