‘Decoupled’ Cratonavis enters the LRT with Zhongjianornis, not Chongmingia

From Phys.org:
“Bizarre Cretaceous bird from China shows evolutionarily decoupled skull and body.”

No. Cratonavis (Figs 1, 2) is simply a relative of Confusciusornis and a closer relative to Zhongjjianornis (Figs 4, 5) in the large reptile tree (LRT, 2196 taxa). Cratonavis slipped neatly between these two taxa. Absolutely nothing is ‘bizarre’ or ‘decoupled’ about this bird.

By contrast, in the large reptile tree (LRT, 2196 taxa) that diversification occurred in the Late Jurassic. The LRT tests 10 Solnhofen birds, including Archaeopteryx. The cladogram from Li et al (Fig 3) employs only one Solnhofen bird, Archaeopteryx.

“This early phylogenetic diversity is overwhelmed by the Ornithothoraces, consisting of the Enantiornithes and Ornithuromorpha, whose members evolved key derived features of crown birds.

Phylogenetic problems are present iin Li et al due to taxon exclusion.

“This disparity consequently circumscribes a large morphological gap between these derived clades and the oldest bird Archaeopteryx”.

In the LRT there are no large morphological gaps.
By employing nearly 2200 taxa the LRT minimizes taxon exclusion.

“The non-ornithothoracine pygostylians, with an intermediate phylogenetic position, are key to deciphering those evolutionary transformations, but progress in their study has been hampered by the limited diversity of known fossils”.

In the LRT theropods with pygostyles evolved several times by convergence. So the erected clade, ‘Pygostylia‘ is polyphyletic.The current diversity of known fossil birds does not hamper progress in the LRT. However, taxon exclusion does hamper progress in the Li et al study.

“Here we report an Early Cetaceous non-ornithothoracine pygostylian, Cratonavis zhui gen. et sp. nov., that exhibits a unique combination of a non-avialan dinosaurian akinetic skull with an avialan post-cranial skeleton, revealing the key role of evolutionary mosaicism in early bird diversification”.

Modular and mosaic evolution is a myth. ‘Pygostylians‘ are polyphyletic. Taxon exclusion and poor reconstructions seem to be at the root of the Li et al problems.

“The unusually elongated scapular and metatarsal one preserved in Cratonavis highlights a breadth of skeletal plasticity, stemming from their distinct developmental modules and selection for possibly raptorial behaviour. Mapped changes in these two elements across theropod phylogeny demonstrate clade-specific evolutionary lability.”

Yes. Every distinct genus and species has elements different from those found in other taxa. This is common sense and the way taxonomy and systematics must operate.

References
Li Z, Wang M, Stidham TA and Zhou Z 2023. Decoupling the skull and skeleton in a Cretaceous bird with unique appendicular morphologies. Nature Ecology & Evolution 96:

wiki/Cratonavis – not yet posted
wiki/Pygostylia

Publicity
Phys.org – Bizarre cretaceous bird from China shows evolutionarily decoupled skull and body