Yuanchuavis skull reconstructed using DGS methods versus free hand

From the Wang et al 2022 abstract:
“Compared to the postcranium, our understanding of the evolutionary assemblage of the characteristic modern bird skull has been hampered by sparse fossil records of early cranial materials, with competing hypotheses regarding the evolutionary development of cranial kinesis among early members of the avialans.”

From Wang et al continued:
“Here, [Figs 3, 4] a detailed three-dimensional reconstruction of the skull of the Early Cretaceous enantiornithine Yuanchuavis kompsosoura allows for its in-depth description, including elements that are poorly known among early-diverging avialans but are central to deciphering the mosaic assembly of features required for modern avian cranial kinesis. Our reconstruction of the skull shows evolutionary and functional conservation of the temporal and palatal regions by retaining the ancestral theropod dinosaurian configuration within the skull of this otherwise derived and volant bird.”

Presenting their reconstruction next to a dromaeosaurid (Wang et al. 2022 their figure 4) is a bit of a phylogenetic reach. More closely related taxa, like any one of the Solnhofen birds, would have been more informative when dealing with this enantiornithine skull.

From Wang et al continued:
“Geometric morphometric analysis of the palatine suggests that loss of the jugal process represents the first step in the structural modifications of this element leading to the kinetic crown bird condition.”

This is the key hypothesis of the paper.Unfortunately, as everyone knows, only the basalmost enantiornithines are close to the ancestry of crown birds. Yuanchuavis is not a basalmost enantiornithine, so convergence may be a larger factor here than the authors appear to surmise.

“The mixture of plesiomorphic temporal and palatal structures together with a derived avialan rostrum and postcranial skeleton encapsulated in Yuanchuavis manifests the key role of evolutionary mosaicism and experimentation in early bird diversification.”