Fossils: Fossils of Cretaceous birds that may lead to rethinking of bird evolution | Nature | Nature’s portfolio

Daniel Field and colleagues report the surprising discovery that birds with fossilized Cretaceous teeth share the same characteristics as modern birds (such as chickens and ducks).natureThe findings challenge long-held assumptions about the origins of birds and may prompt a rethinking of bird evolution and taxonomy.

Modern birds belong to two basic types: Paleognathia and Neognathia. Paleognathians (cassowaries, ostriches, tinamuts, etc.) have cranial skeletons joined together by rigid joints and no soft palate joints. Neognathia (including chickens, ducks, and all other modern birds) have skeletons joined by somewhat loose joints and an articulated palate. Since the ancestors of birds (such as theropod dinosaurs) had assimilated palates, it was previously thought that neognathians evolved from birds with ancient skulls. However, this hypothesis was difficult to test, as the palate is fragile and rarely well preserved in the fossil record. Field et al describe a partial skeleton of a 67-million-year-old species of bird (Janavis finalidens) and show observations that its palate is nearly indistinguishable from that of modern land and waterfowl. This indicates that birds with neognathian skulls evolved first, from which the Paleognathians evolved.

J. finalidens is the closest known bird species to the iconic toothed seabird Ichthyornis, but it weighs more than twice that of the largest Ichthyornis fossil specimen ever found. The study could also show that ichthyophila survived until the end of the Cretaceous period and eventually died out during the mass extinction of bird-like dinosaurs at the end of the Cretaceous period.

doi: 10.1038/s41586-022-05445-y

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