title: Frontoparietal Bone in Extinct Palaeobatrachidae (Anura): Its Variation and Taxonomic Value.
abstract: Palaeobatrachidae are extinct frogs from Europe closely related to the Gondwanan Pipidae, which includes Xenopus. Their frontoparietal is a distinctive skeletal element which has served as a basis for establishing the genus Albionbatrachus. Because little was known about developmental and individual variation of the frontoparietal, and its usefulness in delimiting genera and species has sometimes been doubted, we investigate its structure in Palaeobatrachus and Albionbatrachus by means of X-ray high resolution computer tomography (micro-CT). To infer the scope of variation present in the fossil specimens, we also examined developmental and interspecific variation in extant Xenopus. In adults of extinct taxa, the internal structure of the frontoparietal bone consists of a superficial and a basal layer of compact bone, with a middle layer of cancellous bone between them, much as in early amphibians. In Albionbatrachus, the layer of cancellous bone, consisting of small and large cavities, was connected with the dorsal, sculptured surface of the bone by a system of narrow canals; in Palaeobatrachus, the layer of cancellous bone and the canals connecting this layer with the dorsal surface of the frontoparietal were reduced. The situation in Palaeobatrachus robustus from the lower Miocene of France is intermediate-while external features support assignment to Palaeobatrachus, the inner structure is similar to that in Albionbatrachus. It may be hypothesized that sculptured frontoparietals with a well-developed layer of cancellous (i.e., vascularized) bone may indicate adaptation to a more terrestrial way of life, whereas a reduced cancellous layer might indicate a permanent water dweller.
authors.affiliation: Department of Palaeobiology, Geological Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Zbyněk
authors.initials: Z
authors.lastname: Roček
authors.affiliation: Institut International de Paléoprimatologie et de Paléontologie Humaine, UMR 7262 CNRS, Université de Poitiers, Poitiers, France.
authors.forename: Renaud
authors.initials: R
authors.lastname: Boistel
authors.affiliation: Multiscale Group, Laboratoire Navier, UMR8205-CNRS/ENPC/IFSTTAR/Université Paris-Est, Champs-sur-Marne, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Lenoir
authors.affiliation: Institut de Chimie des Milieux et Matériaux de Poitiers, UMR 7285 Université de Poitiers, UFR SFA, Poitiers, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Mazurier
authors.affiliation: Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts.
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Pierce
authors.affiliation: Sorbonne Universités-CR2P-MNHN, CNRS, UPMC-Paris 6, Muséum National d'Histoire Naturelle, Paris, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Rage
authors.affiliation: Laboratory of Evolutionary Morphology, a.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Smirnov
authors.affiliation: Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Universität Bonn, Bonn, Germany.
authors.forename: Achim H
authors.initials: AH
authors.lastname: Schwermann
authors.affiliation: Institut International de Paléoprimatologie et de Paléontologie Humaine, UMR 7262 CNRS, Université de Poitiers, Poitiers, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Valentin
authors.affiliation: Țării Crişurilor Museum, Oradea, Romania.
authors.forename: Márton
authors.initials: M
authors.lastname: Venczel
authors.affiliation: Department of Archaeology, General Department of Cultural Heritage Rhineland Palatinate, Section Geological History of the Earth, Mainz, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Wuttke
authors.affiliation: X-Ray Micro CT and Nano CT Research Group, CEITEC-Central European Institute of Technology, Brno University of Technology, Brno, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Zikmund
mesh_terms: D000818:Animals; D001001:Anura / Q000033:anatomy & histology* / Q000145:classification*; D005075:Biological Evolution; D005260:Female; D005624:Frontal Bone / Q000033:anatomy & histology*; D010294:Parietal Bone / Q000033:anatomy & histology*; D055114:X-Ray Microtomography
keywords: Albionbatrachus; Anura; Palaeobatrachidae; Palaeobatrachus; Xenopus; development; frontoparietale; variation