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re: Sinopterus - judgement call



I've been reexamining a few characters used to assess the phylogenetic
position of Sinopterus. Previously PAUP found it at the base of the
Pteranodon/Nyctosaurus clade but close to the Tapejaridae and then visa
versa. Presently if I code the nasoantorbital fenestra as higher than
the orbit I get an unresolved branch of the tree in this area. If I code
the NAOF as not higher, I get resolution, with Sinopterus basal to both
higher clades. About 145 other characters are adding weight one way or
the other. What to do? Certainly the in situ position of the NAOF
appears to be slightly higher than the orbit -- but put the skull back
together again and it is not higher-- or at least there doesn't appear
to be much height difference if any. In a lot of pterosaurs, P.
antiquus, for example, the height is about even, too.

Then there's the ontogeny problem. Would that slight thickening at the
convex bend of the premaxillary someday become a crest in the adult
version? It's only slight bigger than similar bumps on Pterorhynchus and
Scaphognathus, which apparently do and do not (respectively) sport a
soft crest. Would the NAOF expand? The shape of the sternal complex, the
relative lengths of the wing and hind limb to the pelvis are key
characters that differentiate this taxon from the others, but those
characters change during growth. Lots to wonder about.

BTW, it may not be the first record of a tapejarid outside of
Gondwanaland (see below), if that Maastrichtian rostrum and mandible
pictured in Wellnhofer 1991, p.1 44 turns out to be tupuxuarid, as it
appears.

David Peters



David Peters


Re: Sinopterus

Just came across the JPEG's for this new pterosaur from China.

Looks like it has a skull that is remarkably similar to that of
Tapejara,
and skeletal proportions that also match fairly closely to those of
Tapejara and Tupuxuara (e.g. a relatively long wingfinger, and
relatively
short metatarsus) so I reckon it must be a tapejarid. First record
outside Gondwanaland too...

Tschuessi

Dave