Re: Doswellia, where does it nest?

[David Marjanovic <david.marjanovic@gmx.at>]

> > If you don't even find the crown-group of Diapsida in your analysis,
> > I can't get rid of the feeling that you don't have enough characters
> > for your huge number of taxa.
>
> Okay. Let's talk about your feelings.

:-)

Well, how many taxa and how many certainly independent characters do you 
have?

> > What about the middle ear?
>
> Okay. What about it?

Crown-group diapsids (Archosauromorpha and Lepidosauromorpha) have one --  
they have a mobile, slender stapes that can be used for hearing, like 
turtles, frogs, and (with extra complications) both clades of crown-group 
mammals. Other diapsids, for example younginiforms, were as deaf as a 
salamander.

http://tolweb.org/Diapsida/ has a longer list of characters:
- "Temporal muscles originating on the dorsolateral surface of the skull 
table. In araeoscelidians and younginiforms, the temporal muscles originate 
from a fascia attached to the lateral edge of the skull table and from the 
ventral surface of the skull table."
- "Prefrontal-nasal suture anterolaterally oriented (Fig. 3D). This suture 
is parasagittal in araeoscelidians, Claudiosaurus, and younginiforms (Fig. 
3A-C)."
- "Squamosal confined to the dorsal half of the skull, except for a narrow 
ventral process supporting the quadrate. The squamosal of younginiforms, 
Apsisaurus, and araeoscelidians is broad ventrally."
- "Strong, broad contact between the paroccipital process and the cheek. 
This contact is weak and often cartilaginous in younginiforms and 
araeoscelidians."
- "Quadrate deeply emarginated posteriorly. The quadrate of saurians 
supports a tympanum in its deep posterior emargination. The quadrate of 
younginiforms has a very shallow emargination that probably did not support 
a tympanum. The quadrate of Apsisaurus and araeoscelidians is not 
emarginated." (Arguably correlated to the stapes characters.)
- "Slender stapes. The stapes of saurians is modified to function as a 
middle ear ossicle to transmit high-frequency air-borne sounds from the 
tympanum to the inner ear. The stapes of younginiforms and araeoscelidians 
is more massive and it is not specialized as a middle ear ossicle." (See 
above.)
- "Dorsal process of stapes with ossified connection to paroccipital process 
of opisthotic. In other taxa, this connection is cartilaginous (or it may 
consist of a tendon), when it is present." (See above.)
- "Large retroarticular process. This is the insertion point for the muscles 
that open the lower jaw. The retroarticular process of araeoscelidians, 
Coelurosauravus, and younginiforms is much smaller."
- "Cleithrum absent. The cleithrum is a dermal bone located on the anterior 
edge of the scapula, dorsal to the clavicle. It is present in 
araeoscelidians, Coelurosauravus, and younginiforms."
- "Lateral manual centrale (a bone in the wrist) small or absent. The 
lateral and medial centralia are approximately of equal size in 
araeoscelidians and in some younginiforms primitively (in 
Acerosodontosaurus)."
- "Fifth distal tarsal absent (this is a small bone in the ankle, proximal 
to the fifth toe). Araeoscelidians, Coelurosauravus, and youngina have five 
distal tarsals."
- "Fifth metatarsal hooked (this bone supports the fifth toe). This bone is 
straight in other diapsids." (Convergence in turtles.)

If we count "middle ear" as one character -- this may or may not be a good 
idea --, we have here ten characters that support the monophyly of the 
diapsid crown-group as traditionally conceived (well, since 1991 anyway). 
Are all ten characters in your matrix?

If yes, I retract my statement for the time being. If not, please put them 
in to see what changes.