A study reconstructs the palate of an Early Cretaceous bird. Cranial kinesis--relative movement between the braincase and the upper jaw--occurs in most living birds. The origin of this ability is poorly understood due to a lack of palatal elements preserved in the fossil record. Han Hu and colleagues describe a fossil specimen of Sapeornis chaoyangensis, an Early Cretaceous stem group bird, which includes an intact vomer--the bone that divides the left and right airways in the inner part of the nose. The authors used high-resolution CT scans to reconstruct a 3D model of the vomer for Sapeornis and for the bird-like dinosaur Sinovenator changii, and reconstructed the palate of Sapeornis. Analysis of the palates of extant birds revealed that the 2 major divisions, Palaeognathae and Neognathae, exhibit distinct vomer morphologies, with cranial kinesis being more developed in the latter. Further, Sinovenator and Sapeornis vomer morphologies resembled that of Palaeognathae, suggesting that these 2 extinct species exhibited limited, if any, cranial kinesis. Additionally, Sapeornis featured an ectopterygoid bone, which is present in nonavian dinosaurs but not in extant birds, further supporting the existence of limited cranial kinesis in Sapeornis. The results suggest that the cranial kinesis observed in modern birds originated within the Neognathae and may have facilitated the diversification and evolutionary success of this lineage, according to the authors.
Article #19-07754: "Evolution of the vomer and its implications for cranial kinesis in Paraves," by Han Hu et al.
MEDIA CONTACT: Han Hu, University of New England, Armidale, AUSTRALIA; tel: +86-18001120556; e-mail: huhan@ivpp.ac.cn
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Proceedings of the National Academy of Sciences