Resumen de Estratigrafía y análisis tafonómico de Bonitasaura salgadoi Apesteguía, en el sitio «La Bonita» (Cretácico superior, Río Negro, Argentina)
Leandro Perez, Alejandro Otero, Sebastián Apesteguía, Pablo A. Gallina
Stratigraphic and taphonomic analysis of Bonitasaura salgadoi Apesteguía (Sauropoda,Titanosauria) at «La Bonita» site (Upper Cretaceous, Río Negro Province, Argentina). «La Bonita» isa fossiliferous locality close to the town of Cerro Policía, Río Negro Province, Argentina. At the quarry areexposed siliceous rocks belonging to the Bajo de la Carpa and Anacleto formations (Santonian-Campanian),separated by an unconformity from the Rentería Formation (Upper Pliocene-Pleistocene). The Bajo de la CarpaFormation is composed of sandstones, fine beds of conglomerates, alternate with pelites and wackes beds. TheAnacleto Formation is composed of sandy to pelitic beds. The Rentería Formation is dominated by conglomerateswith clasts that reach 15 cm in length, included in a sabullitic matrix. The facies analysis suggests a fluvialregime, with a subacuatic control with changes from mid to low energy. The lenticular-shaped sandy channelswith crossed stratification point to an unidirectional flow in the transporting agent and bioclasts. Thetaphonomical analysis suggested that the dinosaur dies close to the river margins, being rapidly incorporated tothe fluvial sediments that sepulted the specimen in successive events. The spatial distribution and bone relationssuggest a very short transport from the source area, with a slight northward movement. The presence of twocaudal vertebrae series with an opisthotonous articulation pattern, suggests that the animal was exposed longenough to permitt the rigor mortis and dissecation. The disarticulation degree also point to some amount ofweathering of the skeleton before being sepulted. However, the exceptional periostium preservation in manycases suggests a very short subaerial exposure.
