Well, as Longipteryx seems to be the topic of the week, I'll post my thoughts on its phylogenetic position. Note my pygostylian phylogeny is-
(Confuciusornithidae (Protopteryx (Jibeinia (Enantiornithes (Patagopteryx, Ornithurae)))))
First, some have suggested this is not a pygostylian. Although the short ulnar feathers look odd for a pygostylian, there are several characters that place it higher than confuciusornithids-
- strut-like coracoid
- elongate hypocleidium
- V-shaped furcula
- metacarpal III longer than metacarpal II
- less than four phalanges on manual digit III
More derived than Protopteryx
- manual phalanx II-2 shorter than II-1.
Less derived than Jibeinia
- manual digit I extends past metacarpal II
Less derived than Ornithothoracines
- manual digit III has ungual
In addition, although I have yet to add sternal characters, note that the sternum is very similar to Protopteryx, almost an intermediate between it and Jibeinia. So, I provisionally assign Longipteryx to the Pygostylia, phylogenetically intermediate between Protopteryx and Jibeinia. I think the skull looks more like Rhamphorhynchus than an ibis, but what do I know? Unfortunately, it seems there are still no ossified uncinates in enantiornithines, as this taxon looks more basal. :-( Perhaps I'll write Details on Longipteryx sometime.....