What is Oculudentavis if it's not a theropod?

In my last post, I argued the recently described Oculudentavis (Xing et al., 2020) is not a theropod.  So what is it?  To answer that question, I entered it into Simoes et al.'s (2018) sauropsid analysis which emphasizes basal lepidosauromorphs and comes out with basal gekkos and nested iguanians even using just morphological characters.  To test Jingmai's avialan hypothesis, I also added Archaeopteryx to the matrix.  The result is 384 MPTs of 2337 steps each.

Strict consensus of 384 MPTs of Simoes et al.'s (2018) analysis after adding Oculudentavis and Archaeopteryx.  Compare to Extended Data Figure 3 of Simoes et al..
As you can see, Oculudentavis resolves as a stem-squamate in a trichotomy with Huehuecuetzpalli and squamates, while Archaeopteryx is an archosauromorph sister to Erythrosuchus.  And this matrix didn't score for scleral ossicle shape, posttemporal fenestra size or maxillary tooth row length.  After scoring Oculudentavis, its teeth are clearly not acrodont, it seems to have a ventral parietal fossa and  lacks an ossified laterosphenoid.  The authors could have made it easier to evaluate by separating the cranial elements in the 3D pdf file.  As it is, a lot of palatal and braincase info is uncertain.  But Huehuecuetzpalli is Albian compared to Oculudentavis' Cenomanian, and has a skull length of 32 mm (19 mm in the juvenile) versus 14 mm in Oculudentavis.


Huehuecuetzpalli skull (top; after Reynoso, 1998), Oculudentavis skull and separate mandible (middle; after Xing et al., 2020), and Archaeopteryx skull (after Rauhut, 2014).

References- Reynoso, 1998. Huehuecuetzpalli mixtecus gen. et sp. nov: A basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodriguez, central Mexico.  Philosophical Transactions of the Royal Society B: Biological Sciences. 353, 477-500.
Rauhut, 2014. New observations on the skull of Archaeopteryx. Paläontologische Zeitschrift. 88(2), 211-221.

Simōes, Caldwell, Talanda, Bernardi, Palci, Vernygora, Bernardini, Mancini and Nydam, 2018. The origin of squamates revealed by a Middle Triassic lizard from the Italian Alps. Nature. 557(7707), 706-709.



Xing, O'Connor, Schmitz, Chiappe, McKellar, Yi and Li,2020. Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579, 245-249.

What is Oculudentavis if it's not a theropod?