Re: New sauropod refs: Rinconsaurus & Amygdalodon

["Tim Williams" <twilliams_alpha@hotmail.com>]

Jaime Headden wrote:

> The question is, where
> are the teeth applied to *Amygdalodon*? I, sadly, do not have Glut's 1997
> encyclopedia, just excerpts from it, so cannot check how he records the 
> data.

Apparently of the seven teeth originally assigned to _Amygdalodon_, only one 
tooth could be found by Rauhut (2003) in the collection of the La Plata 
Museum.  Rauhut removed this tooth from the type material for _Amygdalodon_, 
and restricted the hypodigm to three dorsal vertebra (one of which is 
designated the lectotype).  The reason behind this is that the previous 
hypodigm for _Amygdalodon_ (teeth, three dorsal vertebrae, one cervical 
vertebra, two caudal vertebrae, sacral centrum, and other assorted 
fragments) pertained to two different-sized sauropods.  This sauropod 
material may actually represent the same species; certainly, all the 
individual elements appear to represent a basal eusauropod (except for a 
"partial scapula" which does not appear to come from a sauropod at all).  
However, more material is needed to confirm whether all the sauropod 
material from the type locality actually belongs to a single taxon 
(_Amygdalodon_).

Thus, rather than attach the name _Amygdalodon patagonicus_ to the tooth 
(which is probably indeterminate), Rauhut chose to nominate a dorsal 
vertebra as lectotype, thereby assuring the name _Amygdalodon_ is valid.  If 
the tooth had been nominated as lectotype then _Amygdalodon_ would be a 
nomen dubium, and a new name would have to be given to the dorsals.  (And if 
further material proves that all the sauropod material from the type 
locality does belong to a single taxon after all, then this new species 
would be sunk into _Amygdalodon_ anyway).



Tim

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