title: Microscopic and immunohistochemical analyses of the claw of the nesting dinosaur, Citipati osmolskae.
abstract: One of the most well-recognized Cretaceous fossils is Citipati osmolskae (MPC-D 100/979), an oviraptorid dinosaur discovered in brooding position on a nest of unhatched eggs. The original description refers to a thin lens of white material extending from a manus ungual, which was proposed to represent original keratinous claw sheath that, in life, would have covered it. Here, we test the hypothesis that this exceptional morphological preservation extends to the molecular level. The fossil sheath was compared with that of extant birds, revealing similar morphology and microstructural organization. In living birds, the claw sheath consists primarily of two structural proteins; alpha-keratin, expressed in all vertebrates, and beta-keratin, found only in reptiles and birds (sauropsids). We employed antibodies raised against avian feathers, which comprise almost entirely of beta-keratin, to demonstrate that fossil tissues respond with the same specificity, though less intensity, as those from living birds. Furthermore, we show that calcium chelation greatly increased antibody reactivity, suggesting a role for calcium in the preservation of this fossil material.
authors.affiliation: Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA aem442@drexel.edu.|Department of Biology, Drexel University, Philadelphia, PA 19104, USA.
authors.forename: Alison E
authors.identifier: 0000-0001-5041-6694
authors.initials: AE
authors.lastname: Moyer
authors.affiliation: Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Wenxia
authors.initials: W
authors.lastname: Zheng
authors.affiliation: Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA.|North Carolina Museum of Natural Sciences, Raleigh, NC 27601, USA.
authors.forename: Mary H
authors.initials: MH
authors.lastname: Schweitzer
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000033:anatomy & histology; D025061:Dinosaurs / Q000033:anatomy & histology*; D005241:Feathers; D005580:Fossils; D006724:Hoof and Claw / Q000033:anatomy & histology*; D007633:Keratins / Q000737:chemistry
chemical_list: D007633:Keratins
keywords: beta-keratin; claw sheath; immunofluorescence; scanning electron microscopy-energy dispersive X-ray spectroscopy; transmission electron microscopy