Re: Unorthodoxies in Reptilian Phylogeny [Romer 1971]

[Jocelyn Falconnet <j.falconnet@gmail.com>]

David Peters a écrit :

> Romer states that 
>
> Limnoscelis is a "true primitive reptile."  
> True or false?
>   
*Limnoscelis* is considered as the closest relative of Diadectidae according to 
Laurin and Reisz (1995), Ruta et al. (2003) and a number of other works. Both 
forms the clade Diadectomorpha which is one of the possible sister group of 
Amniota (the relationships of Lepospondyli, Diadectomorpha, and *Westlothiana* 
with Amniota are still disputed).
It's hard to say if Romer was right or not about the taxonomic position of 
*Limnoscelis*. It's not a fact, but the result of a comparative work based on 
observations and interpretations, in a given taxonomic frame. Give me first a 
definition of Reptilia and I could answer your question. According to the most 
consensual one (and not the appropriate one), Reptilia (= Sauropsida) is the 
sister group of Synapsida and do not include *Limnoscelis*.

> "Macrocnemus now appears to be definitely a lepidosaur" 
> True or false?
>   
Same remark. It was a Prolacertiformes til the clade exploded with the revision 
of *Prolacerta* and *Protorosaurus* and the description of new Drepanosauridae 
during the last decade. According to Gottman-Quesada and Sander (2009), 
*Tanystropheus* and *Macrocnemus* form a clade (which should reasonably be 
called Tanystropheidae) close to Archosauriformes than to Lepidosauria. But 
their taxonomic sampling was too small in my opinion, as they included 
*Youngina* as the only non-saurian diapsid. (I don't have the paper within my 
reach but I think they used a simplified version of the analysis of Dilkes 
(1998)). Modesto and Sues (2004) found *Macrocnemus* within a rather classical 
Protorosauria but without *Prolacerta* which appeared as the sister group of 
Archosauriformes (btw, their matrix is also a modified version of that of 
Dilkes (1998)).

--
Jocelyn Falconnet