SGER: Morphological Study of a Key Avian Fossil from Antarctica: New Data from X-Ray Computed Tomography and Histology

First definitive fossil evidence for part of the extant avian radiation in the Cretaceous A longstanding controversy surrounds whether living bird lineages emerged after the extinction of non-avian dinosaurs at the Cretaceous/Tertiary (K/T) boundary or whether these lineages coexisted with non-avian dinosaurs and passed through this mass extinction event. While inferences from biogeography and molecular sequence data have projected most major avian lineages into the early Cretaceous, implying “mass survival” of these lineages at the K/T boundary, the fossil record has been argued to refute this hypothesis, placing a “big bang” of avian radiation only after the end of the Cretaceous.

Other fossil data, fragmentary bones referred to extant bird lineages have been considered inconclusive. None were included in phylogenetic analyses. We identified a partial skeleton from the Maastrichtian of Antarctica as the first Cretaceous fossil definitively placed within the radiation of extant birds.