title: Evolution of dinosaur epidermal structures.
abstract: Spectacularly preserved non-avian dinosaurs with integumentary filaments/feathers have revolutionized dinosaur studies and fostered the suggestion that the dinosaur common ancestor possessed complex integumentary structures homologous to feathers. This hypothesis has major implications for interpreting dinosaur biology, but has not been tested rigorously. Using a comprehensive database of dinosaur skin traces, we apply maximum-likelihood methods to reconstruct the phylogenetic distribution of epidermal structures and interpret their evolutionary history. Most of these analyses find no compelling evidence for the appearance of protofeathers in the dinosaur common ancestor and scales are usually recovered as the plesiomorphic state, but results are sensitive to the outgroup condition in pterosaurs. Rare occurrences of ornithischian filamentous integument might represent independent acquisitions of novel epidermal structures that are not homologous with theropod feathers.
authors.affiliation: Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK p.barrett@nhm.ac.uk.
authors.forename: Paul M
authors.identifier: http://orcid.org/0000-0003-0412-3000
authors.initials: PM
authors.lastname: Barrett
authors.affiliation: Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Canada M5S 2C6.
authors.forename: David C
authors.initials: DC
authors.lastname: Evans
authors.affiliation: Palaeobiology Programme, Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden Subdepartment of Evolution and Development, Department of Organismal Biology, Uppsala University, Norbyvägen 18A, Uppsala 752 36, Sweden.
authors.forename: Nicolás E
authors.initials: NE
authors.lastname: Campione
mesh_terms: D000818:Animals; D005075:Biological Evolution; D025061:Dinosaurs / Q000033:anatomy & histology*; D005241:Feathers / Q000033:anatomy & histology*; D005580:Fossils / Q000033:anatomy & histology*; D034582:Integumentary System / Q000033:anatomy & histology*; D016013:Likelihood Functions; D010802:Phylogeny
keywords: Dinosauria; feathers; integument; phylogeny; scales