title: Melanosomes or microbes: testing an alternative hypothesis for the origin of microbodies in fossil feathers.
abstract: Microbodies associated with fossil feathers, originally attributed to microbial biofilm, have been reinterpreted as melanosomes: pigment-containing, eukaryotic organelles. This interpretation generated hypotheses regarding coloration in non-avian and avian dinosaurs. Because melanosomes and microbes overlap in size, distribution and morphology, we re-evaluate both hypotheses. We compare melanosomes within feathers of extant chickens with patterns induced by microbial overgrowth on the same feathers, using scanning (SEM), field emission (FESEM) and transmission (TEM) electron microscopy. Melanosomes are always internal, embedded in a morphologically distinct keratinous matrix. Conversely, microbes grow across the surface of feathers in continuous layers, more consistent with published images from fossil feathers. We compare our results to both published literature and new data from a fossil feather ascribed to Gansus yumenensis (ANSP 23403). 'Mouldic impressions' were observed in association with both the feather and sediment grains, supporting a microbial origin. We propose criteria for distinguishing between these two microbodies.
authors.affiliation: Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695.
authors.forename: Alison E
authors.initials: AE
authors.lastname: Moyer
authors.affiliation: Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695.
authors.forename: Wenxia
authors.initials: W
authors.lastname: Zheng
authors.affiliation: Physical and Life Sciences Department, Colorado Northwestern Community College, Craig, CO, 81625.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Johnson
authors.affiliation: Section of Vertebrate Paleontology, Carnegie Museum of Natural History, Pittsburgh, PA 15213.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Lamanna
authors.affiliation: Gansu Geological Museum, Lanzhou, Gansu, China, 730030.
authors.forename: Da-qing
authors.initials: DQ
authors.lastname: Li
authors.affiliation: Department of Biodiversity, Earth and Environmental Science, Drexel University, Philadelphia, PA 19104.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Lacovara
authors.affiliation: 1] Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695 [2] North Carolina Museum of Natural Sciences, Raleigh, NC, 27601.
authors.forename: Mary H
authors.initials: MH
authors.lastname: Schweitzer
mesh_terms: D000818:Animals; D002645:Chickens; D005241:Feathers / Q000648:ultrastructure; D005580:Fossils; D020460:Melanosomes; D008830:Microbodies; D008855:Microscopy, Electron, Scanning