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Re: Our current understanding of Mesozoic bird phylogeny

David Marjanovic wrote-

the new Yixianornis paper (Clarke et al., 2006)

I have managed to miss that one. Which journal was it in?

Clarke, J. A., Zhou, Z., and Zhang, F., 2006, Insight into the evolution of avian flight from a new clade of Early Cretaceous ornithurines from China and the morphology of Yixianornis grabaui: Journal of Anatomy, v. 208, p. 287-308.

Two characters of my own (median sternal process expanded distally;
mtIV longer than mtIII) that I thought might affect enantiornithine
relationships.

Yes, but the first looks ontogenetic to me. Or, more probably, _partially_ ontogenetic (there's probably a phylogenetic signal in when in ontogeny the sternum ossifies that far). 

I agree.  Indeed, this is probably true of most sternal process characters.

Caudal vertebral count was revised to be a total
count and not just of free vertebrae.

Good, but how did you count the vertebrae in the pygostyle?

Dalingheornis (a juvenile) hadn't fused its pygostyle yet and has twenty caudals, while the Yixian enantiornithine embryo has ~18. This fits with estimations of ~8-15 caudals being incorporated into the pygostyles of other basal avebrevicaudans.

- *Wyleyia* as the basalmost enantiornithean is interesting.

Very poorly supported. It's less derived than Protopteryx due to the absence of a well-developed fossa on midline of the proximal humerus.

- *Vorona* and *Elsornis* on the next node is also interesting.

Vorona has a few likely positions. After I modified some codings for the entries on my website, Vorona came out as a liaoningornithid instead. This was based on several characters shared with Liaoningornis-
fossa for insertion of capital ligament on femoral head (also in Confuciusornis and Apsaravis+Passer; unknown in Liaoningornis<Gobipteryx and Eoalulavis); metatarsals at least partially fused distally (also in Changchengornis, Avisaurus gloriae and Euornithes; unknown in Eoalulavis); trochlea of metatarsal II subequal in width to III (also in non-enantiornithines and Longipterygidae; unknown in Eoalulavis); metatarsal IV not reduced in width compared to II and III (also in non-enantiornithines and those more basal than Longipteryx; unknown in Eoalulavis).
Another possible position is as a basal euornithine.
Elsornis moved up a couple nodes past Protopteryx and Iberomesornis to be the basalmost euenantiornithine. This position is congruent with the one found in its original description and was found to be highly possible in my earlier tests.

| |?-Jibeinia adult

Oho! What's that?

Jibeinia coded with juvenile characters as unknown. I'll post more on Jibeinia soon.

           |                    `--+--+--Yungavolucris
           |                       |  |--Hebeiornis
           |                       |  |--LP-4450-IEI
           |                       |  `--+--GMV 2158
           |                       |     `--GMV-2159

Curiouser and curiouser...

And largely based on Clarke's IMHO poor trochlear extent character. When it's deleted, Hebeiornis becomes a basal gobipterygid (based on posterolateral sternal processes expanded less than twice minimum width shared with Boluochia and distal end of metatarsal II strongly curved medially).

Yungavolucris falls into an uncertain basal position. It's excluded from Longipterygidae due to its broad trochlea on metatarsal II, from Sinornis+Concornis due to its lack of a strong plantar projection on the medial rim of metatarsal III's trochlea, and from Gobipteryx<Sinornis due to the lack of a strongly anteriorly inclined proximal tarsometatarsal surface. Within the latter clade, it also lacks the gobipterygid synapomorphy of a medially curved metatarsal II trochlea, and three liaoningornithid synapomorphies (metatarsals at least partially fused distally; trochlea of metatarsal II subequal in width to III; metatarsal IV not reduced in width compared to II and III).

LP-4450-IEI (the Catalan nestling) and GMV-2159 (a Yixian juvenile) are more derived than Eocathayornis based on their short manus. Further positioning is probably difficult.

           |                       `--+--Gobipterygidae
           |                          |  |--Boluochia
           |                          |  `--Gobipteryx

Are they held together by anything else than their toothless pmx?

Yes. The distal end of metatarsal II is curved medially (as in Hebeiornis, Avisaurus and Soroavisaurus, which are all gobipterygids in the revised results).

           |                          `--Avisauridae
           |                             |*-Avisaurinae
           |                             |  |--Avisaurus
           |                             |  `--Soroavisaurus
           |                             |--Sinornis
           |                             `--+--Liaoningornithinae
           |                                |  |--Eoalulavis
           |                                |  `--Liaoningornis
           |                                `--Concornithinae
           |                                   |--Concornis
           |                                   `--Neuquenornis

I like this very much! :-) Is there any chance that *Cuspirostrisornis* is in or next to this clade?

Well, the topology changed a bit in the revised version. Here's what's going on my website-
Avisauridae
|*-Jibeinia luanhera
|--Cathayornithidae
| |--Eoenantiornis buhleri
| `--+--Sinornis santensis
| `--+--"Cathayornis" caudatus
| |--Concornis lacustris
| `--Neuquenornis volans
`--+*-Sazavis prisca
|--Liaoningornithidae
| |?-Vorona berivotrensis
| |--Eoalulavis hoyasi
| `--Liaoningornis longidigitus
`--Gobipterygidae
|--Dapingfangornis sentisorhinus
|--Hebeiornis fengningensis
`--+--Boluochia zhengi
`--+*-Nanantius eos
|--Gobipteryx minuta
`--+--Soroavisaurus australis
`--+--Avisaurus archibaldi
`--Avisaurus gloriae

As for Cuspirostrisornis-
The pneumotricipital fossa is character only currently known in euenantiornithines among Mesozoic birds, though uncertain in more basal Enantiornithes besides being absent in the very basal Wyleyia. The slender metatarsal IV is similar to Lectavis and more derived enantiornithines. Cuspirostrisornis seems less derived than Protopteryx due to its narrow metatarsal II trochlea. The elongate ulna is similar to both protopterygids and Otogornis+Eocathayornis. If the illustration is accurate a lateral coracoid process may exclude it from the Iberomesornis+Enantiornis clade. However, the posteromedial sternal processes are like the Longipteryx+Enantiornis clade. Yet the tibiotarsal intercondylar groove is said to be broad, which would be unlike that clade. The short rostrum is unlike longipterygids, yet the toothless maxilla and narrow metatarsal II trochlea are similar. On the other hand, the short nasal process of the premaxilla is like Eocathayornis and more derived enantiornithines (and Protopteryx as well). The concave lateral coracoid and absent olecranal fossa are unlike most members of this clade though. The blunt posteromedial sternal processes are unlike cathayornithids, while the short sternum, posterolateral and posteromedial sternal processes, distally unfused tarsometatarsus and slender metatarsal IV are all unlike liaoningornithids (though the narrow metatarsal II trochlea is similar). The distal end of metatarsal II is not medially curved, unlike gobipterygids, while the toothed premaxilla is unlike the Boluochia+Gobipteryx subclade. This results in Cuspirostrisornis more parsimoniously being a protopterygid, though only a couple more steps are needed to make it a longipterygid or as basal as Lectavis.

           `--Euornithes
              |--Aberratiodontus

I guess its many teeth pull it towards *Yanornis*?

Nope. Tooth count wasn't used by any of the analyses I combined. It's the basalmost enantiornithine in my revised topology though, in a trichotomy with Wyleyia. It's only an enantiornithine based on- sternal posteromedian process acutely narrow (also in Changchengornis, Confuciusornis dui, Hongshanornis and Gansus; absent in Eoalulavis and Liaoningornis); ventrodistal margin of humerus projected significantly distal to dorsodistal margin, distal margin angling strongly ventrally (also in Piksi and Apsaravis). I bet was a euornithine in the prior topology based on its dorsoventrally curved scapula, elongate sternum, and/or elongate postacetabular process.

`--Ornithuromorpha

So you're using the older definition that does not mention *Vorona* :-P 

Seems to be most useful considering Vorona may be an enantiornithine.

Highly unlikely
875 steps- Otogornis as a euornithine ambiortiform
This is Kurochkin's (1999) idea, based on his reinterpretation of the
material. Even if I were to grant Kurochkin's alternative morphology
(coracoid tubercle = procoracoid process), the tree would still be 873 steps
or so, showing Kurochkin's identifications for these are probably wrong.

Oh.

Yup. Several paleornithologists have noted that Otogornis is an enantiornithine as well, though nobody's examined it cladistically in a published analysis yet.

871 steps- Protopteryx and Longipteryx successively closer to Ornithothoraces
This kind of paraphyletic Enantiornithes was proposed by me back in 2001 on the DML, based on six characters, all of which were examined here. Notably, far more enantiornithine characters have been described in it now than were proposed by Zhang et al. (2001). I now officially reject this hypothesis.

Ah. Too bad. The 3rd-finger lengths fitted so well :-)

Now we know Hongshanornis had two phalanges on manual digit III, making its reduction probably convergent between derived enantiornithines and derived euornithines.

Very possible
862 steps- confuciusornithids as enantiornithines
Surprisingly, this reduced version of Sauriurae (which shouldn't be termed
Sauriurae, as it lacks Archaeopteryx) is highly parsimonious. The addition
of Chiappe's characters makes it slightly less so than the traditional
(western) ornithothoracine view.

Surprisingly indeed!

Ornithothoraces is only supported by the following, as far as this matrix goes-
less than thirteen dorsal vertebrae (also in Harpymimus+Ornithomimus and Oviraptoriformes; unknown in Confuciusornithidae); scapulacoracoid mobily jointed (also in Rahonavis and Shenzhouraptor); distal end of posterodistal sternal process fused to sternum (absent in Liaoningornithidae, Cuspirostrisornis, Hesperornis and Ichthyornis); projected carina on sternum (absent in Jibeinia, Longchengornis, Eoalulavis and Hesperornis; also in Mononykinae and Jixiangornis); interclavicular angle <68 degrees (absent in Hesperornis); capital groove developed on proximal humerus (absent in Elsornis, Apsaravis and Ambiortus; also in Gallimimus, Neimongosaurus, Therizinosauridae, Mononykus, Deinonychus and Bambiraptor); dorsal condyle of distal ulna developed as semilunate ridge (absent in Eocathayornis; also in Heyuannia); metacarpal I fused to carpometacarpus (absent in Hebeiornis (ontogenetic?); also in Patagonykus+Mononykus, Avimimus and Heyuannia); less than four phalanges on manual digit III (also in Tyrannosauridae, Caudaipteryx, Jinfengopteryx and Omnivoropterygidae); alula present (also somewhat developed in Microraptor gui).

861 steps- Odontornithes 

:-o

Just four more steps in addition to 857! Wow. Where does *Gansus* go in this case? 

In Odontornithes, if I remember correctly.

860 steps- Apsaravis closer to Carinatae than Hesperornithes
This was suggested in the original description of Apsaravis (Norell and
Clarke, 2001), but found to be slightly less parsimonious by Clarke and
Norell (2002).  The change was due to correcting a few codings between
papers.

In sum, we need a lot more basal hesperornithean fossils, or the long branch of Hesperornithes will continue to attach itself to wherever it wants. 

I guess I could code Enaliornis and see what that does.

Does anything surprising occur in trees with 858 steps? :o) 

Well, the basal enantiornithine tree looks like this now-
Enantiornithes
|*-Wyleyia valdensis
|?-Aberratiodontus wui
`--+*-"Holbotia ponomarenkoi"
  |*-Yungavolucris brevipedalis
  |--Lectavis bretincola
  `--+--Protopterygidae
     |  |?-Cuspirostrisornis houi
     |  |--Protopteryx fengningensis
     |  `?-Noguerornis gonzalezi
     `--+*-Catenoleimus anachoretus
        |*-Longchengornis sanyanensis
        |--Iberomesornis romerali
        `--Euenantiornithes
           |*-"Cathayornis" aberransis
           |--Elsornis keni
           `--+*-Abavornis bonaparti
              |*-Alexornis antecedens
              |*-Kizylkumavis cretacea
              |--Explorornis nessovi
              `--+*-Enantiornis? walkeri
                 |*-Gurilynia nessovi
                 |*-Halimornis thompsoni
                 |*-+--Incolornis silvae
                 |  `--Incolornis martini
                 |*-Largirostrornis sexdentornis
                 |--Longipterygidae
                 |  |--Longipteryx chaoyangensis
                 |  `--Longirostravis hani
                 `--+*-Enantiornis leali
                    |*-Liaoxiornis delicatus
                    |--Dalingheornis liweii
                    `--+--+--Eocathayornis walkeri
                       |  `--Otogornis genghisi
                       `--Avisauridae

In Euornithes, chaoyangiids and Patagopteryx can be rearranged extremely easily. Also, Ambiortus has an uncertain position in the basal part of the clade. Haven't really looked into that part of the tree yet. After doing this bird stuff months ago, I've been busy coding cranial characters lately in my coelurosaur analysis. Almost done with them finally.

Mickey Mortimer