Search

The Bajo de la Carpa Formation (Santonian) of the Neuquén basin (southwestern Argentina) has one of the most complete crocodyliform records of South America, together with the Adamantina and Marília formations of Brazil. In this contribution we report two fragmentary individuals from two different localities of the Bajo de la Carpa Formation: a middle-sized individual (MLP 26-IV-30-2), represented by postcranial remains from the Boca del Sapo locality and a large-bodied individual (MACN Pv-RN 1150), consisting only of snout elements from Paso Córdoba locality. Despite the remains of both specimens are fragmentary, they display anatomical characters of a specialized notosuchian carnivore clade: Baurusuchidae. Our phylogenetic analysis recovers these new individuals as non-baurusuchine baurusuchids, although they take multiple phylogenetic positions on the different most parsimonious trees. These new remains highlight the relevance of the Bajo de la Carpa Formation for understanding the rise of notosuchians during the Late Cretaceous. La formation de Bajo de la Carpa (Santonien) sur le bassin de Neuquén (Sud-Ouest de l’Argentine) possède l’un des enregistrements crocodyliformes les plus complets du continent, ainsi que la formation de Marília au Brésil. Dans cette contribution, nous rapportons deux individus fragmentaires de deux localités différentes de la formation de Bajo de la Carpa: un individu de taille moyenne (MLP 26-IV-30-2), représenté par des restes postcrâniens de la localité de Boca del Sapo et un individu de grande taille (MACN Pv-RN 1150), constitué uniquement d’éléments de museau de la localité de Paso Córdoba. Bien que les restes des deux spécimens soient rares, ils présentent tous deux des caractères anatomiques d’un clade carnivore notosuchien spécialisé : Baurusuchidae. Notre analyse phylogénétique conduit à considérer ces nouveaux individus comme des baurusuchiens non baurusuchinés, bien qu’ils prennent de multiples positions phylogénétiques sur les différents arbres les plus parcimonieux. Ces nouveaux vestiges soulignent la pertinence de la formation Bajo de la Carpa pour comprendre la montée de notosuchiens au cours du Crétacé et leur diversification postérieure. Fil: Leardi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Pol, Diego. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gasparini, Zulma. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Los avances recientes en el registro fósil, la anatomía y la historia evolutiva de las tortugas sudamericanas permiten un análisis exhaustivo de sus cambios en la diversidad y la identificación de eventos importantes de extinción. Con la ruptura de Pangea en el Jurásico Medio, las tortugas comienzan a diversificarse, dando lugar a los principales clados de tortugas sudamericanas, algunos de los cuales sobreviven hasta el presente. El primer pico de diversidad se observa en el Cretácico Temprano. Se reconoce un primer evento de extinción al final del Cretácico Temprano, que afecta principalmente a los Pelomedusoides en las latitudes bajas y que coincide con la separación final de América del Sur de África. La extinción del límite K–Pg afectó profundamente las tortugas en el continente al reducir su diversidad a la mitad. La reducción de la diversidad continuó después de la extinción K–Pg, aproximadamente hasta el Eoceno medio y el aislamiento final del continente de la Antártida. En este “nuevo” continente, las tortugas sobrevivientes continuaron disminuyendo en su diversidad, hasta que una inyección de biodiversidad desde África ayudó a recuperar los niveles de diversidad. El levantamiento de los Andes en el Oligoceno tardío–Mioceno temprano y los cambios climáticos y de hábitat asociados plantearon nuevos problemas para las tortugas. Nuevas inyecciones de biodiversidad ocurrieron al final del Neógeno con el Gran Intercambio Biótico Americano, cuando nuevos clados llegaron desde el Norte. La biodiversidad moderna de las tortugas sudamericanas tomó su forma final solo durante el último millón de años. Recent advances in the fossil record, anatomy, and evolutionary history of South American turtles allow a thorough analysis of their changes in diversity, and to identify several major extinction events. With the onset of the breakup of Pangea in the Middle Jurassic, turtles begin to diversify, giving rise to the main South American turtle clades some of which survive until present. The first peak of diversity was achieved in the Early Cretaceous. A first extinction event is recognized in the end of the Early Cretaceous, affecting mainly the pelomedusoids in northern latitudes and coinciding with the final separation of South America from Africa. The K–Pg boundary mass extinction affected deeply the thriving turtles in South America by reducing their diversity in half. Reduction of diversity continued on the aftermath of the K–Pg extinction, roughly until the middle Eocene and the final isolation of South America from Antarctica. In this “new” continent, the diversity of the surviving turtles continued to decrease, until an injection of biodiversity from Africa, with the arrival of tortoises, which helped to recover the diversity levels. The Andean uplift in Late Oligocene–Early Miocene and the associated climate and habitat changes posed new problems for the turtles of the continent. New injections of biodiversity took place at the end of the Neogene with the Great American Biotic Interchange, as novel clades reached South America from the North. The modern biodiversity of South American turtles took its final shape only during the last million years. Fil: Vlachos, Evangelos. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Randolfe, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Sterli, Juliana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Leardi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Thalattosuchians are a group of Mesozoic crocodylomorphs known from aquatic deposits of the Early Jurassic-Early Cretaceous that comprises two main lineages of almost exclusively marine forms, Teleosauridae and Metriorhynchoidea. Teleosaurids were found in shallow marine, brackish and freshwater deposits, and have been characterized as semiaquatic near-shore forms, whereas metriorhynchids are a lineage of fully pelagic forms, supported by a large set of morphological characters of the skull and postcranial anatomy. Recent contributions on Thalattosuchia have been focused on the study of the endocranial anatomy. This newly available information provides novel evidence to suggest adaptations on the neuroanatomy, senses organs, vasculature, and behavioral evolution of these crocodylomorphs. However, is still not clear if the major morphological differences between teleosaurids and metriorhynchids were also mirrored by changes in the braincase and endocranial anatomy. Based on X-ray CT scanning and digital endocast reconstructions we describe the braincase and endocranial anatomy of two well-preserved specimens of Thalattosuchia, the semiaquatic teleosaurid Steneosaurus bollensis and the pelagic metriorhynchid Cricosaurus araucanensis. We propose that some morphological traits, such as: an enlarged foramen for the internal carotid artery, a carotid foramen ventral to the occipital condyle, a single CN XII foramen, absence of brain flexures, well-developed cephalic vascular system, lack ofsubtympanic foramina and the reduction of the paratympanic sinus system, are distinctive features of Thalattosuchia. It has been previously suggested that the enlarged foramen for the internal carotid artery, the absence of brain flexures, and the hypertrophied cephalic vascular system were synapomorphies of Metriorhynchidae; however, new information revealed that all of these features were already established at the base of Thalattosuchia and might have been exapted later on their evolutionary history. Also, we recognized some differences within Thalattosuchia that previously have not been received attention or even were overlooked (e.g., circular/bilobate trigeminal foramen, single/double CN XII foramen, separation of the cranioquadrate canal from the external otic aperture, Facultad de Ciencias Naturales y Museo

The Cretaceous witnessed the greatest diversity of Gondwanan notosuchian crocodyliforms, which displayed high levels of diversity and a notable array of specialized forms that developed in different ecological niches. Among this diversity, the advanced notosuchians are a clade of mid body sized forms which displays a remarkable abundance but is restricted to two lithological units from the Late Cretaceous of South America, the Adamantina Formation in southestern Brazil and the Bajo de la Carpa Formation in Patagonia (Argentina). The only exceptions known so far were the Late Cretaceous Labidiosuchus from the Marilia Formation in Brazil and Yacarerani from the Cajones Formation in Bolivia. Herein we report a new Cretaceous crocodyliform, Llanosuchus tamaensis gen. nov. et sp. nov., found in the Los Llanos Formation (Campanian?) in northwestern Argentina (La Rioja Province). The small specimen includes well preserved fragments of the cranium and mandible with an estimated skull size of about 9 cm lengths. This crocodyliform shares several derived characters with Notosuchus terrestris from the Bajo de la Carpa Formation (Patagonia) and it was found in a weakly developed sandy paleosol profile formed in wet local conditions but in a region characterized by semi-arid climate and active eolian sedimentation. The presence of a new advanced notosuchian in the Cretaceous of western Gondwana, and its intermediate geographical region between the known South American species (Brazil, Argentina and Bolivia), has interesting implications, and adds another record of an advanced notosuchian in deposits with inferred warm climates and semi-arid paleoenvironments. Finally, Llanosuchus tamaensis supports a Late Cretaceous age for Los Llanos Formation with important geological implications for La Rioja Province. Fil: Fiorelli, Lucas Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentina Fil: Leardi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Hechenleitner, Esteban Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentina Fil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Basilici, Giorgio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentina. Universidade Estadual de Campinas; Brasil Fil: Grellet-tinner, Gerald. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentina. Orcas Island Historical Museum; Estados Unidos

A new crocodyliform specimen is presented here found in the Cerro Castaño Member of the Cerro Barcino Formation (Chubut Group). The material consists of cranial and postcranial remains that represent a new taxon that has strong affinities with Peirosauridae, but also shares derived features present in Araripesuchus. The phylogenetic relationships of this new taxon were tested through a cladistic analysis depicting it as a member of the Peirosauridae. The inclusion of Barcinosuchus within this clade of basal mesoeucrocodylians is supported by the presence of hypapophyses up to the third or fourth dorsal vertebrae, anterolateral facing edge on postorbital, quadrate dorsal surface divided in two planes by a ridge; mandibular symphysis tapering anterirorly in ventral view, lateral surface of dentary convex anterior to mandibular fenestra, distal body of quadrate well developed, anteroposteriorly thin and lateromedially broad. The new specimen broadens the temporal and geographical distribution of Peirosauridae during the Cretaceous of Gondwana, representing the southern-most and the most ancient record of the group in Patagonia. The new material also provides insights on the postcranial anatomy of peirosaurids, a group that has been so far studied almost exclusively from cranial material. © 2009 Elsevier Ltd. All rights reserved. Fil: Leardi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Geología. Cátedra de Paleontología de Vertebrados; Argentina Fil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina

In this contribution, we describe new specimens of Yacarerani boliviensis from the Cajones Formation (Upper Cretaceous) of Bolivia. We focus on the postcranial anatomy of Y. boliviensis, because this anatomical region is completely unknown in other sphagesaurid notosuchians up to the present. At least eight individuals representing almost the entire postcranial skeleton are described. Although the postcranial anatomy of Yacarerani resembles that of other notosuchians in many features, five autapomorphic characters were identified: pedicles of the atlas bearing a lateral bulge; absence of rounded depressions on the dorsal surface of the anterior to middle dorsal vertebrae; coracoid bearing an oblique crest on its lateral surface; lateromedially compressed anterior ungual phalanges; and femur with a shallow depression for the M. puboischiofemoralis internus 1 and M. caudifemoralis longus. Observed variation in the postcranial anatomy of basal mesoeucrocodylians was incorporated as new characters in a phylogenetic analysis, expanding the postcranial information used in current phylogenetic data sets. The phylogenetic analysis depicts Yacarerani forming a clade with Adamantinasuchus, which is positioned at the base of Sphagesauridae. This family is well nested among a clade of ’advanced notosuchians,’ and Mariliasuchus is recovered as its sister group. The cladistic analysis recovered new postcranial synapomorphies for Notosuchia and less inclusive clades, although the fact that many taxa lack postcranial remains limits the number of unambiguous postcranial synapomorphies within Notosuchia. Fil: Leardi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Pol, Diego. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Novas, Fernando Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Suárez Riglos, Mario. Museo de Historia Natural Noel Kempff Mercado; Bolivia