Paleobiodiversity of the Bajo de la Carpa Formation (Santonian, Upper Cretaceous) in the Cerro Overo-La Invernada area, northern Patagonia, Argentina

CRUZADO-CABALLERO, PENÉLOPE; MÉNDEZ, ARIEL HERNÁN; FILIPPI, LEONARDO SEBASTIÁN; JUÁREZ VALIERI, RUBÉN; GARRIDO, ALBERTO CARLOS

Burgos

Jornada; VII Jornadas Internacionales sobre Paleontología de Dinosaurios y su entorno; 2016

Colectivo Arquelógico y Paleontológico de Salas

The Bajo de la Carpa Formation is a Santonian (middle Late Cretaceous) continental unitbelonging to the Neuquén Group of the Neuquén basin, in northwestern Patagonia, Argentina. It is represented at different areas of the basin of fluvial and aeolian sediments. The first fossil vertebrates from the unit were reported at the end of the XIX and early XX centuries in the actual Neuquén city and the Rancho de Ávila (Dolgopol de Sáez, 1928; Huene, 1929; Woodward, 1896, 1901). Subsequently, paleontological work was carried in these localities and others areas of the Neuquén and Río Negro provinces, as Paso Córdoba, La Bonita, Sierra Barrosa, Tratayén, Loma de la Lata, Cañadón Arroyo Seco, Narambuena, and Cerro Overo‐La Invernada. All these previous fieldwork, together with stratigraphic and paleontological revisions allow the recognition of an abundant vertebrate fossil record, which resulted in the recognition of multiple taxa, including dipnoans as the ceratodontiform Ceratodus kaopen and Atlantoceratodus patagonicus (Filippi et al., 2015); turtles, as the chelid Lomalatachelys neuquina, unnamed podocnemidoids and pelomedusoids (Garrido, 2010), the basal serpent Dinilysia patagonica (Bonaparte, 1991); multiple crocodilians, as the long‐limbed ziphosuchians Microsuchus schilleri and Neuquensuchus universitas, the ?advanced notosuchian? Notosuchus terrestris, the stemsebecosuchians Comahuesuchus brachybuccalis and Pehuenchesuchus enderi, the baurusuchids Cynodontosuchus rothi and Wargosuchus australis, the peirosaurid Gasparinisuchus peirosauroides (Bonaparte, 1991; Leardi et al., 2015; Martinelli et al., 2012) and other unnamed forms; pterosaurs represented by an unnamed azhdarchid (Apesteguía et al., 2007); the theropods by the noasaurid Velocisaurus unicus and indeterminated brachyrostrans, a large megaraptorid under study, the alvarezsaurians Alvarezsaurus calvoi and their possible synonym Achillesaurus manazzonei, the avisaurid Neuquenornis volans and the patagopterygiform Patagopteryx deferaisii (Bonaparte, 1991; Ezcurra & Méndez, 2009; Porfiri et al., 2008); the sauropods includes the lithostrotians Rinconsaurus caudamirus, Bonitasaura salgadoi, Traukutitan eocaudata, and Overosaurus paradasorum (de Jesus Faria et al., 2015; Filippi, 2015; Garrido, 2010). Since 2013, a multi‐agency team led by the Museo Argentino Urquiza of Rincón de los Sauces began to work systematically the area Cerro Overo‐La Invernada. These areas are located about fifty kilometres to the south of Rincón de los Sauces city, northeastern Neuquén province. Inthis area there are extensive outcrops sediments of the Bajo de la Carpa Formation, and theoverlying Anacleto Formation. Palaeontological fieldwork of the past three years have allowed significantly increase the knowledge about faunal diversity of the Bajo de la Carpa Formation. The findings includes the small sized derived abelisaurid theropod Viavenator exxoni (Filippi et al., 2016) and several additional brachyrostran abelisaurids, including two partial skulls and a specimen preserving a pelvis; partial elements belonging to megaraptorans; complete eggs preliminary assigned to theropods; multiple lithostrotian sauropod taxa, including an association of three individuals of different size with resembles to Overosaurus paradasorum, an articulated specimen comprising a complete skull and the complete sequence from atlas to the sacrum and both ilia which resembles to Bonitasaura salgadoi, and a large lognkosaurian represented by cervical vertebrae. The ornithopods, a clade not previously reported in the unit is recorded by three individuals, all representing non‐hadrosaurian euiguanodontians: a pubis resembling that of Gasparinisaura, an indeterminated iguanodontian preserving vertebrae, coracoid and ischium, and a large elasmarian represented by an articulated specimen comprising eleven cervical and dorsalvertebrae, ribs, intercostal plates, scapular waist and complete arm. Besides the dinosaurianremains, this area provided materials of a peirosaurid crocodylomorphs comprising a dentary and isolated teeth, several turtles, at least three different forms, including complete caparaces, and dipnoan fishes including ?mummified? specimens. The notorious fossiliferous abundance of continental vertebrates allow to approach multiple actual and future lines of investigation, including palaeobiological aspects as the anatomy, systematics and phylogenetic relationships of several new taxa, the intraspecific and ontogeneticvariability, sympatry among abelisaurids and lithostrotians, comparison with the faunalassemblages from others areas of the basin during the deposition of the Bajo de la CarpaFormation, taphonomic issues, between others.