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Bellosi E.S.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Krause J.M.,Museo Paleontologico Egidio Feruglio
Andean Geology | Year: 2014

Climate-driven changes in terrestrial environments and biomes after the Early Eocene Climatic Optimum are poorly documented from southern continents. Particularly, Middle Eocene-Early Oligocene leaf and pollen data from Central Patagonia (46oS, Argentina) are not sufficient to characterize floristic paleocommunities. Paleosols of the Cañadón Vaca (~45-42 Ma) and Gran Barranca (42-38.5 Ma) members (Sarmiento Formation), studied at Cañadón Vaca, solve such deficiency and help to reconstruct Middle Eocene landscapes in the beginning of the Cenozoic cooling-drying trend. Vitric Entisols, mollic Andisols and andic Alfisols, showing granular structure and diverse micropeds, are cyclically arranged mainly in response to variation in fine volcaniclastic eolian supply, which in turn governed ecosystem stability and maturity. Soils formed in loessic plains crossed by minor ephemeral rivers, supported open herbaceous-arboreal communities which grew in seasonal, subhumid and warm-temperate conditions. Phytoliths produced by Arecaceae, megathermic graminoids, sedges and dicots, from the upper part of the studied unit, represent subtropical savannas with grasses and variable number of palms and other trees. Considering the abundant paleobotanical and paleopedological antecedents of Late Paleocene-Early Eocene warm and humid forested environments in the same region, the lower Sarmiento Formation records the initial expansion of open herbaceous communities and the appearance of grassy habitats during the greenhouse to icehouse transition in the Middle Eocene.

Perez M.E.,Museo Paleontologico Egidio Feruglio | Perez M.E.,CONICET
Journal of Vertebrate Paleontology | Year: 2010

Cavioidea sensu stricto groups three traditionally recognized families that are characterized by hypsodont, double-heart-shaped cheek teeth and moderate hystricognathy: Eocardiidae, Caviidae, and Hydrochoeridae. Eocardiidae was erected to include a diverse assemblage of extinct and plesiomorphic taxa, whereas Caviidae and Hydrochoeridae (the crown group of Cavioidea) include the lineages with extant representatives (cuyes, maras, and capybaras). A new genus and species of Cavioidea sensu stricto, Guiomys unica, is described here from the middle Miocene of west central Patagonia (Argentina). The new taxon is known from mandibular and maxillary fragments with molars, and isolated cheek teeth. A phylogenetic analysis of Cavioidea sensu stricto shows G. unica as the sister taxon of the clade formed by the crown group of Cavioidea sensu stricto ('medialis series'). The new species displays characters states intermediate between eocardiids and the 'medialis series.' The most outstanding character of Guiomys unica is the autapomorphic position of the notch for the insertion of the masseter medialis pars infraorbitalis muscle, isolated from both the masseteric and horizontal crests. This notch is located at the anterior end of the masseteric crest in eocardiids and represents the plesiomorphic state for Cavioidea sensu stricto. In caviids and hydrochoerids, the notch is located at the anterior end of the horizontal crest, the derived state for this character. G. unica allows reinterpretation of the homologies of the mandibular crests in basal cavioids and clarifies the evolutionary origins of crown-group cavioids (Caviidae + Hydrochoeridae). © 2010 by the Society of Vertebrate Paleontology.

Ferrari S.M.,Museo Paleontologico Egidio Feruglio | Ferrari S.M.,CONICET
Journal of Systematic Palaeontology | Year: 2014

Gastropods are represented in the Early Jurassic of Argentina by Vetigastropoda, Caenogastropoda and Opisthobranchia. The present paper describes nine new vetigastropod species from the Early Jurassic marine deposits of the Neuquén Basin: Proconulus? argentinus sp. nov., Chartronella atuelensis sp. nov., Striatoconulus? axialis sp. nov., Guidonia disciformis sp. nov., Ambercyclus andinus sp. nov., Ambercyclus chilcaensis sp. nov., Discohelix sanicoensis sp. nov., Cryptaenia sudamericana sp. nov. and Cryptaenia globosa sp. nov. Another three vetigastropods are reported for the first time in this region – Chartronella gradata Ferrari, Ataphrus mulanguiniensis Ferrari and Colpomphalus? aff. musacchioi Ferrari – extending their palaeobiogeographical distributions in the Andean region of Argentina. Lithotrochus humboldtii (von Buch), Lithotrochus rothi Damborenea & Ferrari, and an undetermined ataphrid species were also retrieved from marine beds of the Neuquén Basin. A quantitative palaeobiogeographical analysis was performed integrating available data on the entire marine vetigastropod species thus far recorded from Argentina. The primary results of the analysis show two clearly discernible palaeobiogeographical units in the Andean region of Argentina. The local vetigastropod species from the Neuquén and Chubut basins may be interpreted considering palaeogeographical control as a determinant in the distribution of these taxa, including the separate evolution of the Neuquén basin until the late Pliensbachian. However, a shallow marine connection between the Neuquén and Chubut basins along the Palaeo-Pacific seaway during the late Pliensbachian–early Toarcian may explain faunal exchange between both basins at that time.http://zoobank.org/urn:lsid:zoobank.org:pub:EBB37780-8571-4B02-9424-A32E1C2A9AC9 © The Trustees of the Natural History Museum, London 2014. All Rights Reserved.

Ezcurra M.D.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Lecuona A.,Museo Paleontologico Egidio Feruglio | Martinelli A.,Federal University of Uberlandia
Journal of Vertebrate Paleontology | Year: 2010

The best-known South American Early Triassic archosauriform belongs to a putative proterosuchid briefly reported by Jos Bonaparte in 1981, collected from the Quebrada de los Fsiles Formation (Puesto Viejo Group, Argentina). This specimen consists of well-preserved natural external molds of a partial postcranium that preserve dorsal vertebrae, osteoderms, a dorsal rib, a possible gastralium, a chevron, a humerus, an ilium, two metapodials, and an ungual. We re-describe this specimen and identify autapomorphies that allow us to recognize Koilamasuchus gonzalezdiazi, gen. et sp. nov. The presence of an iliac blade with a slightly convex dorsal margin and with a maximum length more than 3 times its maximum height places Koilamasuchus within Archosauriformes. A cladistic analysis of basal Archosauriformes positions Koilamasuchus more crownwards than Proterosuchus, Sarmatosuchus, Fugusuchus, and Osmolskina, as the sister taxon of the clade that includes Erythrosuchidae and Archosauria. Proterosuchidae is found to be paraphyletic. The presence of an iliac preacetabular process, a pubic peduncle that forms an angle lower than 45° to the longitudinal axis of the ilium, and dorsal body osteoderms positions Koilamasuchus in Archosauriformes more crownwards than proterosuchids. Koilamasuchus is more basal than erythrosuchids within Archosauriformes because of the presence of dorsal ribs with a poorly developed proximal end. Koilamasuchus importantly increases the diversity of Archosauriformes during the biotic recovery following the Permo-Triassic mass extinction. © 2010 by the Society of Vertebrate Paleontology.

New species of Cryptaulax and Procerithium (Procerithiidae, Caenogastropoda) are reported from the Lower Jurassic (Pliensbachian-Toarcian) marine deposits of west-central Chubut province, Argentinean Patagonia. Three new species are described: Cryptaulax redelii, Procerithium (Rhabdocolpus) patagoniensis and Procerithium (Infacerithum) nodosum; and the diagnoses of Cryptaulax damboreneae Ferrari and Procerithium nulloi (Ferrari) are emended. The new fossils derive from the Mulanguiñeu and Osta Arena formations and expand the known diversity of the Procerithiidae, extending its palaeobioeographical distribution into the South American Jurassic. © 2012 Copyright Taylor and Francis Group, LLC.

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