E and P of Pteros - Notes 1

[david peters <davidrpeters@earthlink.net>]

Finally got to see The Geological Society special publication

Evolution and Paleobiology of Pterosaurs, eds. E. Buffetaut and J-M. Mazin.  
2003

It came out in October, so no breaking news here. I'm late and I'm probably the 
last interested party to get to see it. 

Anyway...

A few notes will probably appear under this banner for the next few days to 
weeks as the chapters are devoured.


Late Triassic Pterosaur from Austria, P. Wellnhofer

This scattered specimen has a wonderfully new sternal complex with twin ventral 
processes which emerge anteriorly like machine guns. Wellnhofer thought they 
would act as the articular facet for the coracoid, but in this specimen the 
ventral base of the coracoid is relatively larger than in any other pterosaur, 
fully one half the length of the tiny sternal complex, and thus probably too 
large to be supported by the slender new processes. A little reconstruction 
reveals that the coracoids fit very well articulating on the sternal rim 
itself. Wellnhofer said he did not see the component parts of the sternal 
complex, as first described by R. Wild, but he drew lines at the margin of 
clavicle/sternum fusion. So the parts are present and I found them clearly 
visible in the photo.

The pelvis shows the decay of the ventral margin, a pattern duplicated in 
Eudimorphodon ranzii and Campylognathoides zitteli (the Paris specimen), so 
placement near these taxa is appropriate. Thereâ??s not much to reconstruct, 
but we're workin' on it anyway.



>>>>>


On the phylogeny and evolutionary history of pterosaurs, D. Unwin


Weâ??re all thankful to finally get the phylogeny of the Pterosauria, complete 
with matrix and character list, into print. A. Kellnerâ??s attempt is also 
included in this volume. Now we can test them!

I think Unwin's choice to lump genera into terminal taxa for his cladogram 
unfortunately will yield chimaera after chimaera and rob him (and us) of a 
chance to see the finer changes happening at the entrances of exits of grades 
and clades. But then again, Iâ??m a splitter. With this system Dave was able to 
generate a matrix grid that was 94% filled in, which is an admirable goal. 
Still, I think itâ??s the subtle character by character blending between taxa 
that makes a cladogram seamless, rather than blocky.

I would have liked to see Daveâ??s appendix 2 list follow standard description 
order (head to tail, forelimb, then hindlimb) rather than jump around the body, 
apparently ordered as phylogenetic changes (starting with Preondactylus).

Some characters like no. 5: â??Humerus, shorter (0), or longer than femur 
(1)â?? would probably have been better stated as â??shorter, or not shorterâ?? 
to take in the possibility of a subequal humerus. 

Character coding had a few problems. 

No. 44. Mandibular rami elevated about symphysis scored for Nyctosaurus and 
Pteranodontidae, but not for Anurognathidae, which is considerably more 
elevated.

No. 60 AOF vs. orbit height scored for Tapejara, Tupuxuara and Azhdarchidae, as 
expected, but missed Anurognathus (not that it would matter much).

I was disappointed to see no palate characters and only one extremity 
comparison. I would think the various proportions of the pedal and manual 
phalanges would be a great place to find hidden phylogenetic patterns. 

Dave was quite right in taking to task my earlier placement of Sordes in the 
Dimorphodontidae. Further work has spun my head around. Yes, Sordes is close to 
Scaphognathus. But it is also equally close to Campylognathoides and 
Dorygnathus and only a step removed from Eudimorphodon and basal 
Dimorphodontidae. It really is kind of a common brown sparrow or shrew-type 
from which so many grander taxa emerged. Funny though, itâ??s closest cousin is 
the new Pterorhynchus found by S. Czerkas, which is not very common looking.

Iâ??ve mentioned the following to Chris Bennett already, but itâ??s worth 
repeating here: 

Iâ??d like to see someone character code a number of the putative juvenile 
specimens and see where they pop up on the cladogram, rather than prejudicially 
ignoring their potential contribution due to their apparent immaturity. 
Remember, there are bee-sized bats and birds in this world. It is an apriori 
assumption not to consider the wee ones. At worst we could find that they lump 
in with some putative adult. At best we might find a clade of micro-pteros. 
Size shrinks and a sprinkling of neotony could easily explain the dimunition of 
â??pterodactyloidâ?? caudals, among other characters.

More later,

David Peters