Reconstructing Carotenoid-Based and Structural Coloration in Fossil Skin

• Published in: Current biology Vol. 26; no. 8; pp. 1075 - 1082
• Main Authors: McNamara, Maria E., Orr, Patrick J., Kearns, Stuart L., Alcalá, Luis, Anadón, Pere, Peñalver, Enrique
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 25.04.2016
• Subjects: Animals; Carotenoids - metabolism; Chromatophores - physiology; Colubridae - physiology; Fossils; Melanins - metabolism; Skin Pigmentation - physiology
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2016.02.038

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. [Display omitted] •Dermal pigment cells are preserved in the skin of a fossil snake•This is the first evidence of carotenoid-based and structural color in fossil skin•The distribution and abundance of pigment cells reveals original color patterns•This opens a new avenue for reconstructing original coloration in fossil animals McNamara et al. report the first example of carotenoid-based coloration in the fossil record and of structural coloration in fossil skin, in a 10 million-year-old snake from the Libros biota of northeastern Spain, and provide a new approach to reconstructing original coloration in fossil vertebrates.