CT data for: Insight into the evolutionary assemblage of cranial kinesis from a Cretaceous bird

The independent movements and flexibility of various parts of the skull,
called cranial kinesis, is an evolutionary innovation that is found in
living vertebrates only in some squamates and crown birds and is
considered to be a major factor underpinning much of the enormous
phenotypic and ecological diversity of living birds, the most diverse
group of extant amniotes. 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. Here, 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.
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. 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.