title: Reconstructing Carotenoid-Based and Structural Coloration in Fossil Skin.
abstract: Evidence of original coloration in fossils provides insights into the visual communication strategies used by ancient animals and the functional evolution of coloration over time [1-7]. Hitherto, all reconstructions of the colors of reptile integument and the plumage of fossil birds and feathered dinosaurs have been of melanin-based coloration [1-6]. Extant animals also use other mechanisms for producing color [8], but these have not been identified in fossils. Here we report the first examples of carotenoid-based coloration in the fossil record, and of structural coloration in fossil integument. The fossil skin, from a 10 million-year-old colubrid snake from the Late Miocene Libros Lagerstätte (Teruel, Spain) [9, 10], preserves dermal pigment cells (chromatophores)-xanthophores, iridophores, and melanophores-in calcium phosphate. Comparison with chromatophore abundance and position in extant reptiles [11-15] indicates that the fossil snake was pale-colored in ventral regions; dorsal and lateral regions were green with brown-black and yellow-green transverse blotches. Such coloration most likely functioned in substrate matching and intraspecific signaling. Skin replicated in authigenic minerals is not uncommon in exceptionally preserved fossils [16, 17], and dermal pigment cells generate coloration in numerous reptile, amphibian, and fish taxa today [18]. Our discovery thus represents a new means by which to reconstruct the original coloration of exceptionally preserved fossil vertebrates.
authors.affiliation: School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland. Electronic address: maria.mcnamara@ucc.ie.
authors.forename: Maria E
authors.initials: ME
authors.lastname: McNamara
authors.affiliation: UCD School of Earth Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Orr
authors.affiliation: School of Earth Sciences, University of Bristol, Queen's Road, Bristol BS8 1RJ, UK.
authors.forename: Stuart L
authors.initials: SL
authors.lastname: Kearns
authors.affiliation: Fundación Conjunto Paleontológico de Teruel-Dinópolis, Avenida Sagunto s/n, 44002 Teruel, Aragón, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Alcalá
authors.affiliation: Consejo Superior de Investigaciones Científicas, Institut de Ciències de la Terra "Jaume Almera," Lluís Solé i Sabarís s/n, 08028 Barcelona, Spain.
authors.forename: Pere
authors.initials: P
authors.lastname: Anadón
authors.affiliation: Museo Geominero, Instituto Geológico y Minero de España, c/ Ríos Rosas 23, 28003 Madrid, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Peñalver
mesh_terms: D000818:Animals; D002338:Carotenoids / Q000378:metabolism*; D002856:Chromatophores / Q000502:physiology; D017812:Colubridae / Q000502:physiology*; D005580:Fossils; D008543:Melanins / Q000378:metabolism; D012880:Skin Pigmentation / Q000502:physiology*
chemical_list: D008543:Melanins; D002338:Carotenoids