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A diverse assemblage of Late Cretaceous dinosaur and bird feathers from Canadian amber.

Science (New York, N.Y.)

Animals, Biological Evolution, Birds, anatomy & histology, Canada, Dinosaurs, Pigmentation, Feathers, Fossils, Amber

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      Abstract

      The fossil record of early feathers has relied on carbonized compressions that lack fine structural detail. Specimens in amber are preserved in greater detail, but they are rare. Late Cretaceous coal-rich strata from western Canada provide the richest and most diverse Mesozoic feather assemblage yet reported from amber. The fossils include primitive structures closely matching the protofeathers of nonavian dinosaurs, offering new insights into their structure and function. Additional derived morphologies confirm that plumage specialized for flight and underwater diving had evolved in Late Cretaceous birds. Because amber preserves feather structure and pigmentation in unmatched detail, these fossils provide novel insights regarding feather evolution.

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      Most cited references 26

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      Plumage color patterns of an extinct dinosaur.

      For as long as dinosaurs have been known to exist, there has been speculation about their appearance. Fossil feathers can preserve the morphology of color-imparting melanosomes, which allow color patterns in feathered dinosaurs to be reconstructed. Here, we have mapped feather color patterns in a Late Jurassic basal paravian theropod dinosaur. Quantitative comparisons with melanosome shape and density in extant feathers indicate that the body was gray and dark and the face had rufous speckles. The crown was rufous, and the long limb feathers were white with distal black spangles. The evolution of melanin-based within-feather pigmentation patterns may coincide with that of elongate pennaceous feathers in the common ancestor of Maniraptora, before active powered flight. Feathers may thus have played a role in sexual selection or other communication.
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        Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds.

        Spectacular fossils from the Early Cretaceous Jehol Group of northeastern China have greatly expanded our knowledge of the diversity and palaeobiology of dinosaurs and early birds, and contributed to our understanding of the origin of birds, of flight, and of feathers. Pennaceous (vaned) feathers and integumentary filaments are preserved in birds and non-avian theropod dinosaurs, but little is known of their microstructure. Here we report that melanosomes (colour-bearing organelles) are not only preserved in the pennaceous feathers of early birds, but also in an identical manner in integumentary filaments of non-avian dinosaurs, thus refuting recent claims that the filaments are partially decayed dermal collagen fibres. Examples of both eumelanosomes and phaeomelanosomes have been identified, and they are often preserved in life position within the structure of partially degraded feathers and filaments. Furthermore, the data here provide empirical evidence for reconstructing the colours and colour patterning of these extinct birds and theropod dinosaurs: for example, the dark-coloured stripes on the tail of the theropod dinosaur Sinosauropteryx can reasonably be inferred to have exhibited chestnut to reddish-brown tones.
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          Development and evolutionary origin of feathers.

           Richard Prum (1999)
          Avian feathers are a complex evolutionary novelty characterized by structural diversity and hierarchical development. Here, I propose a functionally neutral model of the origin and evolutionary diversification of bird feathers based on the hierarchical details of feather development. I propose that feathers originated with the evolution of the first feather follicle-a cylindrical epidermal invagination around the base of a dermal papilla. A transition series of follicle and feather morphologies is hypothesized to have evolved through a series of stages of increasing complexity in follicle structure and follicular developmental mechanisms. Follicular evolution proceeded with the origin of the undifferentiated collar (stage I), barb ridges (stage II), helical displacement of barb ridges, barbule plates, and the new barb locus (stage III), differentiation of pennulae of distal and proximal barbules (stage IV), and diversification of barbule structure and the new barb locus position (stage V). The model predicts that the first feather was an undifferentiated cylinder (stage I), which was followed by a tuft of unbranched barbs (stage II). Subsequently, with the origin of the rachis and barbules, the bipinnate feather evolved (stage III), followed then by the pennaceous feather with a closed vane (stage IV) and other structural diversity (stages Va-f). The model is used to evaluate the developmental plausibility of proposed functional theories of the origin of feathers. Early feathers (stages I, II) could have functioned in communication, defense, thermal insulation, or water repellency. Feathers could not have had an aerodynamic function until after bipinnate, closed pennaceous feathers (stage IV) had evolved. The morphology of the integumental structures of the coelurisaurian theropod dinosaurs Sinosauropteryx and Beipiaosaurus are congruent with the model's predictions of the form of early feathers (stage I or II). Additional research is required to examine whether these fossil integumental structures developed from follicles and are homologous with avian feathers. J. Exp. Zool. (Mol. Dev. Evol.) 285:291-306, 1999. Copyright 1999 Wiley-Liss, Inc.
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            Author and article information

            Journal
            21921196
            10.1126/science.1203344

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