springer.com Earth Sciences : Paleontology Agnolin, Federico, Novas, Fernando E. Avian Ancestors A Review of the Phylogenetic Relationships of the Theropods Unenlagiidae, Microraptoria, Anchiornis and Scansoriopterygidae Although consensus exists among researchers that birds evolved from coelurosaurian theropods, paleontologists still debate the identification of the group of coelurosaurians that most closely approaches the common ancestor of birds. The last 20 years witnessed the discovery of a wide array of avian-like theropods that has considerably amplified the anatomical disparity among deinonychosaurians, some of which resemble Archaeopteryx more than Deinonychus. Among these newly discovered theropods that show remarkable bird-like characteristics are the four-winged theropods Microraptor and Anchiornis, and the unenlagiids Unenlagia, Buitreraptor, and Rahonavis. A bizarre group of minute-sized coelurosaurs, the Scansoriopterygidae, also exhibits some avian similarities that lead some authors to interpret them as more closely related to birds than other dinosaurs. With the aim to explore the phylogenetic relationships of these coelurosaurians and birds, we merged recently published Springer integrative databases, resulting in significant changes in the topological distribution of taxa 2013, IX, 96 p. 18 illus., 6 within Paraves. We present evidence that Dromaeosauridae, Microraptoria, Unenlagiidae, and 1st illus. in color. Anchiornis + Xiaotingia form successive sister taxa of Aves, and that the Scansoriopterygidae edition are basal coelurosaurians not closely related to birds. The implications in the evolutionary sequence of anatomical characters leading to birds, including the origin of flight, are also considered in light of this new phylogenetic hypothesis. Printed book Softcover Order online at springer.com/booksellers Printed book Springer Nature Customer Service Center GmbH Softcover Customer Service ISBN 978-94-007-5636-6 Tiergartenstrasse 15-17 69121 Heidelberg £ 49,99 | CHF 65,00 | 54,99 € | Germany 60,49 € (A) | 58,84 € (D) T: +49 (0)6221 345-4301 Available [email protected] Discount group Science (SC) Product category Brief Series SpringerBriefs in Earth System Sciences Other renditions Softcover ISBN 978-94-007-5638-0 Prices and other details are subject to change without notice. All errors and omissions excepted. Americas: Tax will be added where applicable. Canadian residents please add PST, QST or GST. Please add $5.00 for shipping one book and $ 1.00 for each additional book. Outside the US and Canada add $ 10.00 for first book, $5.00 for each additional book. If an order cannot be fulfilled within 90 days, payment will be refunded upon request. Prices are payable in US currency or its equivalent. ISBN 978-94-007-5636-6 / BIC: RBX / SPRINGER NATURE: SCG39000 Part of .