A primitive hadrosaurid from southeastern North America and the origin and early evolution of ‘duck-billed’ dinosaurs

<i>Eotrachodon orientalis</i> gen. et sp. nov. (latest Santonian of Alabama, southeastern U.S.A.) is one of the oldest and most basal hadrosaurid dinosaurs and the only hadrosaurid from Appalachia (present day eastern North America) with a preserved skull. This taxon possesses a relatively derived narial structure that was until now regarded as synapomorphic for saurolophine (solid-crested or crestless) hadrosaurids. Maximum parsimony analysis places <i>E. orientalis</i> as the sister taxon to Saurolophidae (Saurolophinae + Lambeosaurinae). Character optimization on the phylogeny indicates that the saurolophine-like circumnarial structure evolved by the Santonian following the split between saurolophines and lambeosaurines but prior to the major hadrosaurid radiation. Statistical dispersal-vicariance analysis posits an Appalachian ancestral area for Hadrosauridae and subsequent dispersal of their ancestors into Laramidia (present-day western North America) during the Cenomanian. http://zoobank.org/urn:lsid:zoobank.org:pub:3AD914D2-A3A5-45FD-8C94-5EE80461FEBC SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Prieto-Márquez, A., G. M. Erickson, and J. A. Ebersole. 2016. A primitive hadrosaurid from southeastern North America and the origin and early evolution of ‘duck-billed’ dinosaurs. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1054495