58390 20200221144319.0 doi 10.1371/journal.pone.0153026 sideral 97275 ART-2016-97275 eng (orcid)0000-0002-7210-1033 Moreno-Azanza, Miguel Combined use of electron and light microscopy techniques reveals false secondary shell units in Megaloolithidae eggshells 2016 Access copy available to the general public Unrestricted Abnormalities in the histo- and ultrastructure of the amniote eggshell are often related to diverse factors, such as ambient stress during egg formation, pathologies altering the physiology of the egg-laying females, or evolutionarily selected modifications of the eggshell structure that vary the physical properties of the egg, for example increasing its strength so as to avoid fracture during incubation. When dealing with fossil materials, all the above hypotheses are plausible, but a detailed taphonomical study has to be performed to rule out the possibility that secondary processes of recrystallization have occurred during fossilization. Traditional analyses, such as optical microscopy inspection and cathodoluminescence, have proven not to be enough to understand the taphonomic story of some egg-shells. Recently, electron backscatter diffraction has been used, in combination with other techniques, to better understand the alteration of fossil eggshells. Here we present a combined study using scanning electron microscopy, optical microscopy, cathodoluminescence and electron backscatter diffraction of eggshell fragments assigned to Megaloolithus cf. siruguei from the Upper Cretaceous outcrops of the Cameros Basin. We focus our study on the presence of secondary shell units that mimic most aspects of the ultrastructure of the eggshell mammillae, but grow far from the inner surface of the eggshell. We call these structures extra-spherulites, describe their crystal structure and demonstrate their secondary origin. Our study has important implications for the interpretation of secondary shell units as biological or pathological structures. Thus, electron backscatter diffraction complements other microscope techniques as a useful tool for understanding taphonomical alterations in fossil eggshells. info:eu-repo/grantAgreement/ES/MINECO/CGL2013-46169-C2-1-P info:eu-repo/grantAgreement/ES/MINECO/CGL2014-53548-P info:eu-repo/semantics/openAccess by http://creativecommons.org/licenses/by/3.0/es/ 2.806 2016 MULTIDISCIPLINARY SCIENCES 15 / 63 = 0.238 2016 Q1 T1 1.236 2016 Agricultural and Biological Sciences (miscellaneous) 2016 Q1 Medicine (miscellaneous) 2016 Q1 Biochemistry, Genetics and Molecular Biology (miscellaneous) 2016 Q1 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion (orcid)0000-0002-4970-6333 Bauluz, Blanca Universidad de Zaragoza (orcid)0000-0003-1732-9155 Canudo Sanagustín, José Ignacio Universidad de Zaragoza (orcid)0000-0002-8427-6199 Gasca, José Manuel Torcida-Baldor, Fidel 2000 655 Universidad de Zaragoza Dpto. Ciencias de la Tierra Área Paleontología 2000 120 Universidad de Zaragoza Dpto. Ciencias de la Tierra Área Cristalografía Mineralog. 11, 5 (2016), e0153026 [17pp] PLoS One PloS one 1932-6203 2336766 http://zaguan.unizar.es/record/58390/files/texto_completo.pdf Versión publicada 105304 http://zaguan.unizar.es/record/58390/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:58390 articulos driver 2020-02-21-13:40:38 ARTICLE