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Re: Alamosaurus as biggest North American sauropod
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. "When you
hear hoofbeats think horses, not zebras." If an when a second sauropod
taxon is positively identified from this stratigraphic and geographic
level, the remains in question can be either left as they are,
re-assigned, or considered dubious.
Assuming from the outset that any fragmentary remains may represent a
new taxon rather than being conservative and using parsimony to assign
them to an already known taxon from which they cannot be
differentiated just leads to over-inflated estimates of diversity, as
in the paper discussed here:
On Wed, Dec 7, 2011 at 5:10 PM, Jocelyn Falconnet <email@example.com> wrote:
> From what I understood in the paper, here is the reasoning of the authors
> for assigning these three bones to *Alamosaurus*:
> - Late Cretaceous sauropods are all titanosaurians
> - cervical vertebra with wide cotyle => as in *Alamosaurus*,
> *Malawisaurus*, and *Puertasaurus*
> - cervical vertebra with lateral pneumatic fossae => as in *Alamosaurus*,
> *Rapetosaurus*, *Malawisaurus*, and *Saltasaurus*
> - no relevant feature on the caudal vertebra and femur
> - no evidence for more than one sauropod taxon from the Maastrichtian of US
> "We therefore refer the new specimens to *A. sanjuanenis*, based on
> stratigraphic and geological parsimony, and the similarity of SMP
> VP−1850 to cervical vertebrae from Texas (Lehman and Coulson 2002), and
> SMP VP−1625 to the caudal series from Utah (Gilmore 1946)."
> Stratigraphic and geological parsimony ?! WTF, if I may say so !
> I recognize that these remains are indeed very interesting for indicating
> the presence of a giant sauropod in the Maastrichtian of the US and their
> possible belonging to *Alamosaurus*, but I think the authors are too much
> optimistic, taxonomically speaking. No need to be a specialist to understand
> that they belongs likely to a titanosaurian but there is no positive
> evidence for its assignment to *Alamosaurus* - and if stratigraphy or
> geology were taxonomically relevant, we would know it ! Hell, there is not
> even a "cf." or an "aff." in the identification of the specimens. Of which
> two are... indeterminate titanosaurians (just read the text).
> So... please, don't do that anymore.
> Time to go to bed,
> Le 07/12/2011 18:14, Ben Creisler a écrit :
>> From: Ben Creisler
>> A new paper in Acta Palaeontologica Polonica:
>> Denver W. Fowler and Robert M. Sullivan (2011)
>> The first giant titanosaurian sauropod from the Upper Cretaceous of North
>> Acta Palaeontologica Polonica 56 (4), 2011: 685-690
>> Argentinosaurus (Cenomanian, Argentina) is generally accepted as being the
>> largest dinosaur so far discovered and is one of several giant titanosaurian
>> sauropods known from the Upper Cretaceous of South America and Asia, but
>> surprisingly not from North America. Here we present the first evidence of
>> giant titanosaurian sauropods from the Upper Cretaceous of North America:
>> two enormous vertebrae and a partial femur, from the Naashoibito Member of
>> the Ojo Alamo Formation, New Mexico, and referred to Alamosaurus
>> sanjuanensis. One of the new vertebrae, a posterior cervical, is comparable
>> in size to a posterior cervical described for Puertasaurus: an
>> Argentinosaurus−sized titanosaurian from the Maastrichtian of Argentina.
>> This makes A. sanjuanensis the largest dinosaur from North America, and
>> among the largest in the world. These findings indicate that A. sanjuanensis
>> is diagnosed based on immature remains, which may have implications for
>> cladistic analyses.