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Re: Alamosaurus as biggest North American sauropod



Am 09.12.2011 01:25, schrieb Tim Williams:

 Matthew Martyniuk <martyniuk@gmail.com> wrote:

> I don't see the issue with using parsimony. In fact I have kind of
> an issue when people don't use it. If the remains can't be
> differentiated from _A. sanjuanenis_, and there is no evidence to
> suggest multiple taxa were present in this environment, it should
> be considered _A. sanjuanenis_ until evidence to the contrary can
> be produced.

 As a rule of thumb, this "rule" is unevenly applied. For example,
 Carpenter and Tidwell (2004) referred all sauropod material from the
 Arundel Formation to a single taxon. All the Arundel sauropod
 material was consistent with the presence of a single species, which
 took the name _Astrodon johnsoni_. In the process, _Pleurocoelus
 nanus_ and _P. altus_ were considered to be subjective junior
 synonyms of _Astrodon johnsoni_, a taxon that was originally
 established on material that is not diagnostic at the genus level
 (tooth + tooth fragment).

 On the other hand, Wilson and Upchurch (2003) did *not* combine
 _Titanosaurus indicus_ and _Antarctosaurus septentrionalis_ into a
 single taxon in their revision of the titanosaur material from the
 'Sauropod bed' of the Lameta Formation at Bara Simla. This was
 despite the fact that this study found no reason to recognize more
 than one species at Bara Simla. The Conclusion makes this clear:
 [...]

Carpenter & Tidwell seem to have thought "if there's no evidence for multiple taxa, don't split". Wilson & Upchurch seem to have thought "if there's no evidence for lumping, don't sink established names, even when there's no evidence that would support splitting either". Both agree "if there's no evidence, don't act" -- they just disagree on what counts as acting...