III Congreso Latinoamericano de Paleontología de Vertebrados - Neuquén, Patagonia, Argentina - 2008
FIRST ABELISAURID POSTCRANIAL REMAINS FROM FUTALOGNKO QUARRY (PORTEZUELO FORMATION, UPPER TURONIAN-CONIACIAN) AND ITS IMPLICATIONS Juárez Valieri, Rubén D.; Berrondo, Martín R.; Calvo, Jorge O. & Porfiri, Juan D. Centro Paleontológico Lago Barreales (CePaLB). Universidad Nacional del Comahue. Ruta Provincial N° 51, km 65. Neuquén, Argentina.
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The Neuquén basin (northwestern Patagonia, Argentina) is the most prolific depositional area in South America with respect to remains of Cretaceous dinosaurs. In this basin the remains of abelisaurids and more basal abelisauroid theropods are reported from the late Hauterivian-early Barremian La Amarga Formation, to the late Campanian-early Maastrichtian Allen Formation. In the upper Turonian-Coniacian Portezuelo Formation (Río Neuquén Subgroup, Neuquén Group), theropod dinosaurs are reported from two principal areas, both in the Neuquén Province. The local fauna of the northern coast of Los Barreales lake includes the basal tetanuran Megaraptor, the alvarezsaurian Patagonykus, the dromaeosaurids Unenlagia, Neuquenraptor, and a new form, and a variety of indeterminated forms represented by teeth. In the local fauna of Sierra del Portezuelo, there are present all these taxa plus a possible galliform and a basal abelisauroid. The presence of abelisaurid abelisauroids was incorrectly asserted by Novas et al. (2005), which mentioned Ekrixinatosaurus novasi from this stratigraphic unit. The real stratigraphic procedence of this taxon is the Candeleros Formation, of Albian-early Cenomanian age in the Bajo de Añelo area, as originally indicated by Calvo et al. (2004). Then, currently no definitive abelisaurid abelisauroids has been reported from the Portezuelo Formation. New material (MUCPv 1245) assignable to Abelisauridae was found in the Futalognko quarry, northern coast of Lago Barreales, and consists of a left transverse process of a caudal vertebra. It is well preserved, and presents an expanded distal end, characteristic of abelisaurids. This element present a very moderate posterior expansion, opossite to the condition present in Carnotaurus, which lacks the posterior expansion, and also to that of Ilokelesia and Ekrixinatosaurus, both of which display a strong posterior expansion subequal to the anterior. In this regard, MUCPv 1245 is more similar to Aucasaurus and a new taxon from the Candeleros Formation (Porfiri et al. 2007). The anterior expansion comprises almost half of the total anteroposterior lenght of the distal extreme, showing the characteristic awllike proyection present in Aucasaurus (Coria et al. 2002). The distal border of the transverse process is sinusoidal in shape and the anterior expansion forms an acute angle with the anterior border of the transverse process medial to the distal expansion. This morphology is strongly reminiscent of Aucasaurus, and clearly different from that of the remaining abelisaurids. The only one difference between the new Lago Barreales form and Aucasaurus is the absence of the rugosity in the distal border of the transverse process. The new material consitutes the first definitive evidence of Abelisauridae from the Portezuelo Formation, and increases the diversity of theropods from this stratigraphic unit. Calvo, J.O.; Rubilar-Rogers, D. & Moreno, K. 2004. A new abelisauridae (Dinosauria: Theropoda) from northwest Patagonia. Ameghiniana, 41(4): 555-563 Coria, R.A.; Chiappe, L.M. & Dingus, L. 2002. A new close relative of Carnotaurus sastrei Bonaparte 1985 (Theropoda: Abelisauridae) from the Late Cretaceous of Patagonia. Journal of Vertebrate Paleontology, 22(2): 460-465. Novas, F.E.; Ezcurra, M.D. & Agnolin, F.L. 2006. Humerus of a basal abelisauroid theropod from the Late Cretaceous of Patagonia. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" – Paleontología, 8(1): 63-68. Porfiri, J.D.; Calvo, J.O.; Gandossi, P. & dos Santos, D. 2007. Nuevos registros de Theropoda en una nueva localidad fosilífera del Cretácico de Patagonia, Argentina. 20° Congresso Brasileiro de Paleontologia, Anais: 196.
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