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Abstract
Paulina-Carabajal, A. & Coria, R.A. 15.4.2015. An unusual theropod frontal from the Upper Cretaceous of north Patagonia. Alcheringa 39, 514–518. ISSN 0311-5518
We report an isolated left frontal (MCF-PVPH 320) corresponding to a medium-sized theropod dinosaur from the Portezuelo Formation (Coniacian) of northern Patagonia. It shows a unique combination of traits that are not present in any other known Cretaceous theropod from South America. MCF-PVPH 320 is robust and anteroposteriorly short, with a flat and smooth dorsal surface largely excavated by the supratemporal fossa. Endocranially, the olfactory bulb impression is elongate, and the olfactory tract impression is markedly shortened anteroposteriorly. MCF-PVPH 320 differs greatly from the frontals of Late Cretaceous theropods, such as abelisaurids, megaraptorines and carcharodontosaurids. In contrast, character states including the thickness of the bone, V-shaped frontoparietal suture, reduced participation on the orbital margin and markedly short olfactory tract impression suggest the presence of an unknown mid-sized to large allosauroid for the Portezuelo Formation.
Ariana Paulina-Carabajal [[email protected]], CONICET-Museo Carmen Funes, Av. Córdoba 55 (8318), Plaza Huincul, Neuquén, Argentina; Rodolfo A. Coria [[email protected]], CONICET-Instituto de Paleobiología y Geología, Universidad Nacional de Río Negro. Av. Roca 1242 (8332), Gral. Roca, Río Negro, Argentina.
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Acknowledgements
We thank the curators A. Kramarz (Museo Bernardino Rivadavia, Buenos Aires, Argentina), R. Schoch (SMNS), J. Gardner (TMP) and M. Carrano (USNM) for the access to the specimens under their care. The comments and corrections made by the editor, S. McLoughlin, and the reviewers, F. Novas and P. Currie, greatly improved this manuscript. We also thank CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) for financial support.