Re: Sereno's (2005) new definitions

[Tim Williams <twilliams_alpha@hotmail.com>]

Phil Bigelow wrote:

> Could someone give an example of a metataxon?

_Lagosuchus talampayensis_ (type species for _Lagosuchus_) is a metataxon.  
Sereno and Arcucci (1994; JVP 14: 53-73) declared _L. talampayensis_ to be a 
nomen dubium.

The fact that the _L. talampayensis_ material lacks autapomorphies is alone 
insufficient justification to declare the species a nomen dubium, IMHO.  The 
situation is complicated by the suggestion that the holotype for _L. 
talampayensis_ may be a composite of more than one species, with the 
forelimb material possibly hailing from a different taxon to the hindlimbs 
and vertebrae.  (When it comes to archosaurs from the Ischichuca, this 
problem of chimeric taxa pops up again and again.)  However, if the 
_Lagosuchus_ type material is indeed from a single species, then 
_Lagosuchus_ is certainly distinguishable from all other basal 
dinosauromorphs, including _Marasuchus lilloensis_.  In fact, even if the 
forelimbs don't belong to _Lagosuchus_, the hindlimbs appear to be distinct 
from those of most other basal dinosauromorphs, though perhaps not 
_Marasuchus_.

Cheers

Tim