Re: questions about the Odontochelys study

[Tim Williams <tijawi@yahoo.com>]

David Peters wrote:

> I repeat: > Which species on the non-turtle side of the
> equation?
> 
> +++++++++++++++
> 
> Still wondering: which _species_? (¡primo importante!)

It's all in:

deBraga M., and Rieppel O. (1997). Reptile phylogeny and the interrelationships 
of turtles. Zool. J. Linn. Soc. 120: 281-351.

Some groups (e.g., Eosauropterygia) are coded as a clade, whereas others (e.g., 
_Placodus_) are coded as individual genera.

> If placodonts (cyamodonts) then the teeth are wrong, etc. etc. 

Ummm...why?  The dentition in no way precludes turtle affinities with 
Sauropterygia.  If placodont teeth are different from _Odontochelys_ teeth, it 
only means that one or both of these two groups diverged from the dentition 
found in their most recent common ancestor.  There's nothing 'wrong' about that.

BTW, nobody is arguing that turtles evolved directly from placodonts (or 
nothosaurs, or plesiosaurs...)  Or vice versa.  The phylogeny in question 
recovers turtles (Testudinata) and sauropterygians as sister taxa - not as 
ancestor-descendent pairings  (I'm getting a sense of deja vu here...) 

> If nothosaurs and plesiosaurs, well... um... I'm
> still looking for some synapomorphies.

BTW, deBraga and Rieppel (1997 list ten synapomorphies uniting Testudinata 
(their Testudines) and Sauropterygia.

> Wouldn't something slow and lumbering fit better?

You mean like pareiasaurs?  Nah, not necessarily.  Not if the common ancestor 
was aquatic.  This ancestor might certainly be slow on land, but adept in the 
aquatic medium.
 


Cheers

Tim