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Exceptionally preserved tadpoles from the Miocene of Libros, Spain: ecomorphological reconstruction and the impact of ontogeny upon taphonomy

Authors

  • MARIA E. MCNAMARA,

  • PATRICK J. ORR,

  • STUART L. KEARNS,

  • LUIS ALCALÁ,

  • PERE ANADÓN,

  • ENRIQUE PEÑALVER-MOLLÁ


Maria E. McNamara [maria.mcnamara1@ucd.ie], Patrick J. Orr [patrick.orr@ucd.ie], UCD School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland; Stuart L. Kearns [stuart.kearns@bristol.ac.uk], Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Rd, Bristol BS8 1RJ, UK; Luis Alcalá [alcala@dinopolis.com], Fundación Conjunto Paleontológico de Teruel-Dinópolis, Avda. Sagunto s/n, 44002 Teruel, Aragón, Spain; Pere Anadón [panadon@ija.csic.es], Consejo Superior de Investigaciones Científicas, Institut de Ciències de la Terra ‘Jaume Almera’, Lluís Solé i Sabarís s/n 08028, Barcelona, Spain; Enrique Peñalver-Mollá [e.penalver@igme.es], Museo Geominero, Instituto Geológico y Minero de España, C/ Ríos Rosas 23, E-28003 Madrid, Spain;

Abstract

McNamara, M.E., Orr, P.J., Kearns, S.L., Alcalá, L., Anadón, P. & Peñalver-Mollá, E. 2010: Exceptionally preserved tadpoles from the Miocene of Libros, Spain: ecomorphological reconstruction and the impact of ontogeny upon taphonomy. Lethaia, Vol. 43, pp. 290–306.

The Libros exceptional biota from the Upper Miocene of NE Spain includes abundant frog tadpoles (Rana pueyoi) preserved in finely laminated lacustrine mudstones. The tadpoles exhibit a depressed body, short tail, low tail fins, dorso-laterally directed eyes and jaw sheaths; these features identify the Libros tadpoles as members of the benthic lentic ecomorphological guild. This, the first ecomorphological reconstruction of a fossil tadpole, supports phylogenetic evidence that this ecology is a conserved ranid feature. The soft-tissue features of the Libros tadpoles are characterized by several modes of preservation. The space occupied previously by the brain is defined by calcium carbonate, the nerve cord is defined by calcium phosphate, and jaw sheaths and bone marrow are preserved as organic remains. Gut contents (and coprolites adjacent to specimens) comprise ingested fine-grained sedimentary detritus and epiphyton. The body outline and the eyespots, nares, abdominal cavity, notochord, caudal myotomes and fins are defined by a carbonaceous bacterial biofilm. A similar biofilm in adult specimens of R. pueyoi from Libros defines only the body outline, not any internal anatomical features. In the adult frogs, but not in the tadpoles, calcium phosphate and calcium sulphate precipitated in association with integumentary tissues. These differences in the mode of preservation between the adult frogs and tadpoles reflect ontogenetic factors. □Anuran, ecology, soft-tissue, tadpoles, taphonomy.

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