STIDHAM, Thomas A., Museum of Paleontology, Dept. of Integrative Biology, and Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720-4780
Although the phylogenetic relationships of birds outside the crown clade are fairly well resolved, the phylogeny of extant birds is highly controversial. Analyses of molecular, morphological, and paleontological data each support radically different sets of neornithine relationships. However, integrative phylogenetic analyses of molecular and morphological data (including fossils) yield concordant phylogenies of extant bird groups when multiple taxa from all hypothesized clades are included in the analyses. The data support the basal position of tinamous within the Paleognathae and the Galliformes and Anseriformes as the most basal neognaths. All of the available evidence supports the identification of many Late Cretaceous fossils as anseriforms. A relatively complete record of anseriform fossils from the Late Cretaceous, early and late Paleocene, and early Eocene points to a Cretaceous diversification of all four "family" level clades of anseriforms: the Anhimidae (screamers), Anseranatidae (magpie goose), Presbyornithidae (extinct clade of long-legged ducks), and Anatidae (true ducks and geese). Not only were these clades present in the Cretaceous and Paleogene, but they also were abundant and diverse with wide geographic distributions throughout their early history. Presbyornithidae appear to have been the dominant group of anseriforms through the Late Cretaceous and Paleogene, ranging in body size from the size of a small plover up to the size of a small goose. The known stratigraphic distributions of the anseriform fossils appear to show that the terminal Cretaceous extinction had little to no effect on ducks.