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Palazzesi L.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Palazzesi L.,Jodrell Laboratory | Barreda V.D.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Cuitino J.I.,University of Buenos Aires | And 3 more authors.
Nature Communications

The Patagonian steppe - a massive rain-shadow on the lee side of the southern Andes - is assumed to have evolved ∼15-12ǎ €‰Myr as a consequence of the southern Andean uplift. However, fossil evidence supporting this assumption is limited. Here we quantitatively estimate climatic conditions and plant richness for the interval ∼10-6ǎ €‰Myr based on the study and bioclimatic analysis of terrestrially derived spore-pollen assemblages preserved in well-constrained Patagonian marine deposits. Our analyses indicate a mesothermal climate, with mean temperatures of the coldest quarter between 11.4ǎ €‰°C and 16.9ǎ €‰°C (presently ∼3.5ǎ €‰°C) and annual precipitation rarely below 661ǎ €‰mm (presently ∼200ǎ €‰mm). Rarefied richness reveals a significantly more diverse flora during the late Miocene than today at the same latitude but comparable with that approximately 2,000ǎ €‰km further northeast at mid-latitudes on the Brazilian coast. We infer that the Patagonian desertification was not solely a consequence of the Andean uplift as previously insinuated.© 2014 Macmillan Publishers Limited. All rights reserved. Source

Abello M.A.,Laboratorio Of Sistematica Y Biologia Evolutiva Lasbe | Candela A.M.,Museo de La Plata
Journal of Vertebrate Paleontology

This contribution presents a morphofunctional analysis of the previously unknown appendicular skeleton of the paucituberculatans Palaeothentes minutus and Palaeothentes lemoinei from the Santa Cruz Formation (late early Miocene, Santa Cruz province, Argentina), performed in order to infer their locomotor behavior. In addition, a cladistic analysis was conducted to explore the phylogenetic information of postcranial features of Palaeothentes in the context of Marsupialia. The results indicate that Palaeothentes would have been an agile cursorial dweller, with leaping ability, similar to the extant paucituberculatan Caenolestes fuliginosus and the didelphid Metachirus nudicaudatus. This mode of locomotion is evidenced mainly by the following features: proximal location of the deltopectoral crest and bicipital tuberosity, reflecting rapid flexion at the gleno-humeral and elbow joints, respectively; shape of the humero-ulnar and humero-radial joints (deep and high humeral trochlea, deep olecranon fossa, deep trochlear notch, mediolaterally broad proximal trochlear crest), denoting a marked stability for flexion and extension; restrictive acetabulum, showing emphasized congruence at the hip joint; lengthened ischium and prominent femoral tubercle and ischial tuberosity, indicating an increased mechanical advantage of the rectus femoris and hamstring muscles; proximally projected greater trochanter, demonstrating a relatively great mechanical advantage of the gluteal muscles; and configuration of the upper ankle, lower ankle, and transverse tarsal joints, indicative of restrictive rotational movements (right angle between the medial and lateral astragalotibial facets, distal and proximal calcaneo-cuboid facet halves forming a right angle). A cladistic analysis positions Palaeothentes as the sister taxon to the extant Caenolestes, demonstrating that postcranial features support the monophyly of Paucituberculata. © 2010 by the Society of Vertebrate Paleontology. Source

Pocco M.E.,CONICET | Posadas P.,Laboratorio Of Sistematica Y Biologia Evolutiva Lasbe | Lange C.E.,CONICET | Cigliano M.M.,CONICET
Systematic Entomology

The Andes, the world's longest mountain chain, harbours great taxonomic and ecological diversity. Despite their young age, the tropical Andes are highly diverse due to recent geological uplift. Speciation either followed the orogeny closely or occurred after the Andean uplift, as a result of subsequent climatic changes. Different scenarios have been proposed to explain the diversification of high Andean taxa. The Melanoplinae grasshopper Ponderacris Ronderos & Cigliano is endemic to the eastern slopes of the Andes of Peru and Bolivia, mostly distributed between 1000 and 4000 m above sea level. Diversification in several montane habitats of Bolivia and Peru allows tests via cladistic analysis of distinct possible geographic modes of speciation. Eight species are recognized, with three described here as new with revised diagnostic morphological characters provided: Ponderacris carlcarbonellisp.n.,P. chulumaniensissp.n. and P. amboroensissp.n. Cladistic analyses of 15 species (8 ingroup and 7 outgroup) and 38 morphological characters, under equal and implied weighting, confirm the monophyly of Ponderacris. Characters from the external morphology and colour pattern provided less phylogenetic information than did the male abdominal terminalia and phallic complex. Species distributed in the Peruvian Andes constituted a monophyletic group, whereas those from the Bolivian Andes formed a basal paraphyletic grade. Dispersal-vicariance analysis resulted in one ancestral distribution reconstruction indicating that the most recent common ancestor was distributed in the Lower Montane Yungas of Bolivia. Eleven dispersal and one vicariant events are postulated, with a South-to-North speciation pattern coincident with progressive Andean uplift. Vicariance could relate to fragmentation of montane forest during the dry intervals of the late Cenozoic. From the Bolivian area, ancestral Peruvian Ponderacris may have dispersed northward, coinciding with the rise of the Andes. Ten of 11 dispersal events occurred at terminal taxa and are likely to be recent. However, diversification of Ponderacris cannot be explained solely by the South-to-North speciation hypothesis, but may also include both vicariance and dispersal across barriers influenced by Pleistocene climatic cycles. © 2013 The Royal Entomological Society. Source

Abello M.A.,Laboratorio Of Sistematica Y Biologia Evolutiva Lasbe
Biological Journal of the Linnean Society

The Paucituberculata is an endemic group of South American marsupials, recorded from the early Cenozoic up to the present. In this report, the most comprehensive phylogenetic analysis of Paucituberculata to date is presented. Fifty-seven terminal species were scored for 74 new and re-examined characters. Homologies of dental characters used in previous systematic studies were critically reviewed to evaluate their inclusion in the analysis. Phylogenetic results corroborated two major paucituberculatan clades, Palaeothentoidea and Caenolestoidea, and the main palaeothentoid groupings: Pichipilidae, Palaeothentidae, and Abderitidae. Taxon sampling and reinterpretations of molar cusp and crest homologies played an important role in the generation of new phylogenetic hypotheses. The main differences with respect to previous phylogenies were focused on palaeothentoid relationships: Palaeothentes boliviensis and Pilchenia lucina are not members of Palaeothentidae but instead clustered with Pilchenia intermedia and P. antiqua, forming the sister-group of a Palaeothentidae+Abderitidae clade, and Titanothentes simpsoni, previously considered a palaeothentine, is nested within the Acdestinae clade. Based on the time-calibrated phylogeny, the following stages in the paucituberculatan evolutionary history are suggested: origin of the group, in the Paleocene to early Eocene at the latest, split of Caenolestoidea and Palaeothentoidea clades during the late early to middle Eocene, evolutionary radiation of palaeothentid and abderitid lineages near the Oligocene-Eocene boundary, and decreased diversity and extinction of palaeothentoids during the middle Miocene. © 2013 The Linnean Society of London. Source

We review the taxonomy of two South American orders of Metatheria (Mammalia) of Colhuehuapian age (early Miocene): Microbiotheria and Polydolopimorphia. First, we comment and discuss on the cusp homologies of the upper and lower molars of the Argyrolagoidea (Polydolopimorphia). Second, we offer results of a phylogenetic analysis of the Microbiotheriidae (Microbiotheria). Third, we analyze all Colhuehuapian Microbiotheria and Polydolopimorphia known up to date: Order Microbiotheria, Family Microbiotheriidae: Pachybiotherium acclinum Ameghino, Pachybiotherium sp., Clenia minuscula Ameghino, Oligobiotherium divisum Ameghino, Eomicrobiotherium mykerum sp. nov., Microbiotherium sp., and Microbiotheriidae indet.; Order Polydolopimorphia, Suborder Bonapartheriiformes, Superfamily Argyrolagoidea, Family Argyrolagidae: Proargyrolagus argentinus sp. nov. and Anargyrolagus primus Carlini, Pascual and Goin; Family Patagoniidae: Patagonia peregrina Pascual and Carlini; Argyrolagoidea indet. Finally, we add knowledge on the Colhuehuapian Didelphoidea, describing an indeterminate species referable to this superfamily, and comment on the identity of "Microbiotherium" gutierrezi Simpson, recognizing the new combination Coona gutierrezi. Source

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