Spheroolithid eggshells in the Lower Cretaceous of Europe. Implications for eggshell evolution in ornithischian dinosaurs |
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| Institution: | 1. Institute of Geology AS CR, v.v.i., Rozvojová 269, 165 02 Praha 6, Czech Republic;2. National Museum, Václavské náměstí 68, 115 79 Praha 1, Czech Republic;1. Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran;2. Nano-Electronic Center of Excellence, Thin Film and Nano Electronic Lab, School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran;3. Institut für Chemie, AG Elektrochemie, Technische Universität Chemnitz, D-09107 Chemnitz, Germany;1. Institut Català de Paleontologia Miquel Crusafont (ICP), Carrer de l''Escola Industrial 23, 08201 Sabadell, Barcelona, Spain;2. Grupo Aragosaurus-IUCA, Paleontología, Facultad de Ciencias, Universidad de Zaragoza, C/ Pedro Cerbuna, 12, 50009 Zaragoza, Spain;1. Natuurhistorisch Museum Maastricht, de Bosquetplein 6-7, 6211 KJ Maastricht, The Netherlands;2. P.O. Box 295, Granger, TX, USA;3. Piet Heinstraat 6, 2628 RK Delft, The Netherlands;1. Colecciones de Paleontología de Invertebrados y Paleobotánica, Museo Nacional de Ciencias Naturales, 28006 Madrid, Spain;2. Departamento de Paleontología (Grupo de Investigación Procesos Bióticos Mesozoicos), Universidad Complutense de Madrid, 28040 Madrid, Spain;3. Departamento de Geología y Geografía (Grupo de Investigación IberCreta), Universidad de Alcalá, 28871 Alcalá de Henares, Spain |
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| Abstract: | Early Cretaceous spheroolithid eggshells have always been extremely scarce, unlike their putative egg layers, ornithopod dinosaurs, which are ubiquitous in Early Cretaceous ecosystems. In this paper, we re-evaluate eggshells previously assigned to the oofamily Elongatoolithidae, an oofamily related to derived theropod dinosaurs (including maniraptorans and oviraptorids), and reassign them to the oofamily Spheroolithidae, on the basis of the lack of a squamatic ultrastructure, and the presence of a prolatocanaliculate pore system and undulating extinction, typical of spheroolithid eggshells. We erect a new oogenus, Guegoolithus to include material previously reported as Macroolithus turolensis Amo-Sanjuan, Canudo and Cuenca-Bescós 2000, and new material from several lower Barremian localities of the Maestrazgo Basin in Spain. Guegoolithus eggshells exhibit an acicular radial ultrastructure in the lower part of the shell units, which develops into a tabular radial ultrastructure in the upper part, giving an appearance of a two-layered eggshell in thin sections that is not seen in SEM pictures. These features fill the gap between the two-layered prismatic eggshell of ceratopsians and the prolatospherulitic ornithopod eggshell of derived hadrosaurs. |
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| Keywords: | Ornithopod Elongatoolithidae Parataxonomy Spain Maestrazgo Basin |
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