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RE: Our current understanding of Mesozoic bird phylogeny



I coded Enaliornis based on Galton and Martin (2002) and it came out as sister to Ornithurae sensu Chiappe. This is due to it lacking dorsal central fossae, having a shallow tibiotarsal intercondylar fossa, and a rounded distal articular surface of metatarsal II. Placing it in Hesperornithes is one step longer, and as several hesperornithine characters it has weren't in the matrix (short broad femur; elongate triangular cnemial crest; proximally deep tarsometatarsus; dorsolateral ridge on metatarsal IV), it is most parsimoniously a hesperornithine. When constrained to be a hesperornithine, synapomorphies of that clade are- dorsal series completely heterocoelous; intercotylar eminence on tarsometatarsus; metatarsal IV projects distally past III. Gansus has the same position (sister taxon of Carinatae) whether Enaliornis is a hesperornithine or not.

I also decided to code Potamornis and Asiahesperornis. Asiahesperornis is sister to Hesperornis based on the wide metatarsal IV; while Potamornis is at least as derived as Apsaravis, but outside Gansus+Carinatae.

evelyn sobielski wrote-

What about _Yungavolucris_? The specimen does not look
like it walked a lot but IIRC it's neither too well
adapted for perching. Is there anything Mesozoic
around which has similar proportions? (Is there
*anything* with similar proportions?)

Hesperornithines, Boluochia and Longipteryx all have metatarsal IV longer than III (as was probably the case for Yungavolucris), though the former was opposite in what metatarsals it reduced in width. Of course, what reason is there to think Yungavolucris was an avisaurid?


Geography suggests against it though, or else
ocean-crossing ability would have been present before
the full mobility of the shoulder girdle evolved (it
was not yet present in _Confuciusornis_, preventing an
effective, modern-bird-type recovery stroke).

We really don't have an idea of the geographical range of confuciusornithids outside of Liaoning and North Korea. What really suggests the enantiornithine identity is the presence of so many other apparently enantiornithine elements in the El Brete assemblage, though I think an ornithurine bone was found there too.


Mickey Mortimer