Did Oculudentavis have an antorbital fenestra?

Some say: Yes.
Others say: No.

You decide. 
Here are two CT scans (Figs. 1, 2), one from the left and the other from the right with overlays interpretating skull sutures, enlarged from the previous presentation.

Figure 1. CT scan from Xing et al. 2020, colors added to show antorbital fenestra. Note the wrinkling of the maxilla reacting to the twisting of the tiny, fragile skull during taphonomy.

Figure 1. CT scan from Xing et al. 2020, colors added to show antorbital fenestra. Note the wrinkling of the maxilla (green) reacting to the twisting of the tiny, fragile skull during taphonomy.

Now, perhaps, you can see the difficulty
in determining whether or not an antorbital fenestra was present in Oculudentavis. DGS makes things easier by segregating bones with color. All interpretations are up for discussion. I hope you’ll agree, DGS overlays facilitate such discussions better than line tracings do.

Figure 1. CT scan of Oculudentavis from Xing et al. 2020, colors added. Antorbital fenestra here is mailer than in Cosesaurus, but still visible.

Figure 2. CT scan of Oculudentavis from Xing et al. 2020, colors added. Antorbital fenestra here is mailer than in Cosesaurus, but still visible.

The antorbital fenestra
in Cosesaurus (Fig. 3) and Oculudentavis (Figs. 1, 2) is only one trait among many linking these basal members of the Fenestrasauria with derived members in the Pterosauria. No single trait is ‘key’. Between the Middle Triassic (Cosesaurus) and the Early Cretaceous (Oculudentavis) the antorbital fenestra could have grown larger, as it did in pterosaurs, or disappear entirely. It’s only one trait. No one trait is that important in a phylogenetic analysis that includes 238 traits.

Figure 2. Cosesaurus nasal crest (in yellow).

Figure 3. Cosesaurus nasal crest (in yellow).

Some workers doubt
that Cosesaurus (Fig. 3) had an antorbital fenestra. Again, you decide. The large reptile tree  (LRT, 1656+ taxa) nests Cosesaurus basal to pterosaurs and other fenestrasaurs.

Final thought:
With cosesaurs in the Early Cretaceous, it might seem possible to spawn a second origin for pterosaur-like flyers… but that never happened. Only in the Middle Triassic were genes and environs in lock-step with one another to produce basal pterosaurs.


References
Ellenberger P and de Villalta JF 1974. Sur la presence d’un ancêtre probable des oiseaux dans le Muschelkalk supérieure de Catalogne (Espagne). Note preliminaire. Acta Geologica Hispanica 9, 162-168.
Ellenberger P 1978. L’Origine des Oiseaux. Historique et méthodes nouvelles. Les problémes des Archaeornithes. La venue au jour de Cosesaurus aviceps (Muschelkalk supérieur) in Aspects Modernes des Recherches sur l’Evolution. In Bons, J. (ed.) Compt Ren. Coll. Montpellier 12-16 Sept. 1977. Vol. 1. Montpellier, Mém. Trav. Ecole Prat. Hautes Etudes, De l’Institut de Montpellier 4: 89-117.
Ellenberger P 1993. Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
Sanz JL and López-Martinez N 1984. The prolacertid lepidosaurian Cosesaurus aviceps Ellenberger & Villalta, a claimed ‘protoavian’ from the Middle Triassic of Spain. Géobios 17: 747-753.
Xing L, O’Connor JK,; Schmitz L, Chiappe LM, McKellar RC, Yi Q and Li G 2020. Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579 (7798): 245–249.

wiki/Oculudentavis
wiki/Cosesaurus

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