Re: synapsids (was RE: pdf request)

[tyazbeck@comcast.net]

I might add that DP, though he is a good artist when painting life 
reconstructions, draws skeletal pictures without reconstructing the skull of 
many reptiles (i.e. he depicts them like they are preserved: crushed, as it is 
in situ) Some of his images are pretty accurate, though.

----- Original Message ----- 
From: "David Marjanovic" <david.marjanovic@gmx.at> 
To: "DML" <dinosaur@usc.edu> 
Sent: Wednesday, June 13, 2012 6:05:03 PM 
Subject: Re: synapsids (was RE: pdf request) 

>  That said, it has been occasionally suggested that Diadectes is a 
>  basal synapsid, although the majority of studies place it outside 
>  crown-group amniotes. 

Not just the majority, but all done after 1992 or so (arguably 1998), 
and all with a decent taxon sampling. I like the idea, but the data 
don't. Diadectomorpha and Amniota are sister-groups. 

(Diadectomorpha contains the herbivorous Diadectidae, the carnivorous 
*Tseajaia*, and the carnivorous, probably amphibious and crocodile-like 
*Limnoscelis*.) 

>  I will leave it for others to comment on detail, if they wish 
>  (David? Mickey?). But in brief, Peter's analyses have a lot to be 
>  desired in terms of anatomical interpretation, methodological 
>  approaches, etc. 

A few years ago, David Peters kindly sent me an early version of his 
analysis. It turned out that: 
-- he had misinterpreted at least a few published line drawings of 
skulls, inferring a completely wrong three-dimensional shape from them; 
-- he had no idea how to make a data matrix for specifically 
phylogenetic analysis. That is, he didn't even _try_ to avoid correlated 
characters. There were lots of them! 

I have told him so at every opportunity, in private and in public, ever 
since then. He has never even tried to argue that I was wrong; nor has 
he ever claimed, let alone tried to show, that he had corrected any such 
mistakes. 

You will notice I haven't mentioned his "photointerpretation technique" 
( = pareidolia) above. That is probably an additional problem even 
outside of pterosaurs. Next Tuesday, on the way to Teruel*, I'll stop by 
in Barcelona and have a look at *Cosesaurus* so I can compare it to his 
interpretation of it, which may be entirely correct but is based on a 
seriously crappy photo. 

* 10th annual meeting of the European Association of Vertebrate 
Palaeontologists. 

>  The wealth of data (genetic, genomic, morphological, developmental, 
>  etc.) pretty securely place turtles and traditional diapsids 
>  together in at least some combination, and the skeletal data for 
>  parareptiles being closer to diapsids than to synapsids is very 
>  strong. 

Exactly. 

>  The idea of a synapsid-archosaur or synapsid-diapsid clade clade has 
>  a long history (Diaptosauria; early non-computerized cladistic 
>  analyses, etc.) And you can certainly pick out a few characters to 
>  support it (thecodonty, for one). But it doesn't pop out in the 
>  really comprehensive studies of Permo-Triassic critters. 

Exactly. BTW, mosasaurs, snakes, and diadectids are thecodont, too, but 
the earliest synapsids (like varanopids) are not, and the sister-group 
to all other diadectids (IIRC) has an intermediate condition.