Are diadectomorphs really reptiles?

[David Peters <davidpeters@att.net>]

D. Marjanovic wrote:

<The Scottish sites from the middle Early Carboniferous have not yielded 
amniotes so far, despite containing the terrestrial-looking *Lethiscus*, 
*Westlothiana* and *Casineria*, so that probably means that there weren't any 
amniotes 335 Ma ago yet. That said, *Casineria* -- originally, like 
*Westlothiana* before it, announced as the world's oldest amniote -- is poorly 
preserved (most notably, the skull is missing), has only received a brief 
description, and has IIRC never been included in a phylogenetic analysis!

The closest relatives of Amniota -- *Solenodonsaurus* and Diadectomorpha -- are 
only known from layers younger than the oldest known amniotes. So, they don't 
help either. The next closest relatives are the lepospondyls, which are common 
335 Ma ago (*Lethiscus* and most likely *Westlothiana* belong there).>



Casineria has a sister taxon from younger strata that does have a skull. Even 
without that Latter Day cousin, you can still put Casineria into a cladistic 
analysis and arrive at another conclusion.

Solenodonsaurus and Diadectomorpha as amniote cousins? That's tradition. And 
even you will have to admit, they stand out like two cats at a dog convention. 
Go back to the chalkboard and you'll find a spectral continuum of morphological 
change in sister taxa. 

Diadectes never had gills!

David Peters
davidpeters@att.net