Presence of diminutive hadrosaurids (Dinosauria: Ornithopoda) in the Maastrichtian of the south-central Pyrenees (Spain)

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Abstract

In recent years a rich and diverse fauna of hadrosaurid dinosaurs has been described in the Upper Cretaceous of the Pyrenees. Recent fieldwork carried out in the upper Maastrichtian levels of the Tremp Formation, in the south-central Pyrenees (province of Huesca, northeastern Spain), has allowed us to recover diminutive fossil bones referable to hadrosaurid dinosaurs. To date, small-sized specimens had not been reported in the area. The remains consist of small vertebrae and fragmentary long bones found in a relatively small area, so it is assumed that they probably belong to individuals of a single population. A morphological examination and a histological study reveal that they represent specimens of advanced ontogenetic stage and allow the identification of an undescribed taxon of small-bodied hadrosaurids. In other parts of Europe, discoveries of small dinosaurs have been linked to insularity. These findings bring to light the smallest hadrosaurid known in Europe to date. ; This paper forms part of the projects CGL2010-16447, CGL2010-18851/BTE and CGL2013-47521-P, subsidized by the Spanish Ministerio de Economia y Competitividad and the European Regional Development Fund. In addition the Government of Aragon ("Grupos Consolidados'' and "Direccion General de Patrimonio Cultural'') has subsidized the fieldwork. The second author received a postdoctoral grant from the Ministerio de Ciencia, Tecnologia e Innovacion Productiva del Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET). The study of the specimens housed at the NHM (London) has been suported by a study grant funded by the Caja de Ahorros de la Inmaculada (Zaragoza) to the second author in 2006. The manuscript has greatly benefited from reviews by Edina Prondvai (MTA-ELTE Lendulet Dinosaur Research Group, Budapest) and David B. Weishampel (Johns Hopkins University - School of Medicine, Baltimore). Special thanks also are owed to J.I. Ruiz-Omenaca (Museo Jurasico de Asturias-MUJA, Colunga) and Xabier Pereda-Suberbiola (Universidad del ...