The Cranial Osteology and Feeding Ecology of the Metriorhynchid Crocodylomorph Genera Dakosaurus and Plesiosuchus from the Late Jurassic of Europe

• Autores: Young, Mark T.; Brusatte, Stephen L.; Brandalise de Andrade, Marco; Desojo, Julia Brenda; Beatty, Braian L.; Steel, Lorna; Fernández, Marta Susana; Sakamoto, Manabu; Ruiz Omeñaca, José Ignacio; Schoch, Rainer
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: metriorhynchid crocodylomorph; Dakosaurus-Plesiosuchus; Late Jurassic; Europe
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Background: Dakosaurus and Plesiosuchus are characteristic genera of aquatic, large-bodied, macrophagous metriorhynchid crocodylomorphs. Recent studies show that these genera were apex predators in marine ecosystems during the latter part of the Late Jurassic, with robust skulls and strong bite forces optimized for feeding on large prey. Methodology/Principal Findings: Here we present comprehensive osteological descriptions and systematic revisions of the type species of both genera, and in doing so we resurrect the genus Plesiosuchus for the species Dakosaurus manselii. Both species are diagnosed with numerous autapomorphies. Dakosaurus maximus has premaxillary 'lateral plates'; strongly ornamented maxillae; macroziphodont dentition; tightly fitting tooth-to-tooth occlusion; and extensive macrowear on the mesial and distal margins. Plesiosuchus manselii is distinct in having: non-amblygnathous rostrum; long mandibular symphysis; microziphodont teeth; tooth-crown apices that lack spalled surfaces or breaks; and no evidence for occlusal wear facets. Our phylogenetic analysis finds Dakosaurus maximus to be the sister taxon of the South American Dakosaurus andiniensis, and Plesiosuchus manselii in a polytomy at the base of Geosaurini (the subclade of macrophagous metriorhynchids that includes Dakosaurus, Geosaurus and Torvoneustes). Conclusions/Significance: The sympatry of Dakosaurus and Plesiosuchus is curiously similar to North Atlantic killer whales, which have one larger 'type' that lacks tooth-crown breakage being sympatric with a smaller 'type' that has extensive crown breakage. Assuming this morphofunctional complex is indicative of diet, then Plesiosuchus would be a specialist feeding on other marine reptiles while Dakosaurus would be a generalist and possible suction-feeder. This hypothesis is supported by Plesiosuchus manselii having a very large optimum gape (gape at which multiple teeth come into contact with a prey-item), while Dakosaurus maximus possesses craniomandibular characteristics observed in extant suction-feeding odontocetes: shortened tooth-row, amblygnathous rostrum and a very short mandibular symphysis. We hypothesise that trophic specialisation enabled these two large-bodied species to coexist in the same ecosystem.
Fil: Young, Mark T.. University of Edinburgh; Reino Unido
Fil: Brusatte, Stephen L.. American Museum of Natural History; Estados Unidos. Columbia University; Estados Unidos
Fil: Brandalise de Andrade, Marco. Universidade Federal do Rio Grande do Sul; Brasil
Fil: Desojo, Julia Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina
Fil: Beatty, Braian L.. New York College of Osteopathic Medicine; Estados Unidos
Fil: Steel, Lorna. Natural History Museum; Reino Unido
Fil: Fernández, Marta Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina
Fil: Sakamoto, Manabu. University of Bristol; Reino Unido
Fil: Ruiz Omeñaca, José Ignacio. Universidad de Oviedo; España
Fil: Schoch, Rainer. Staatliches Museum für Naturkunde, Stuttgart; Alemania