Museo Argentino de Ciencias Naturales Bernardino Rivadavia

Buenos Aires, Argentina

Museo Argentino de Ciencias Naturales Bernardino Rivadavia

Buenos Aires, Argentina
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Noetinger S.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2015

Devonian deposits in northwestern Argentina were historically studied with stratigraphical purposes, since these layers conform the source rocks of the producing basins of the region. A fairly well preserved palynomorph assemblage, from the Tonono Formation, provides an opportunity to perform the first quantitative analysis to study the evolution of diversity in the succession. Two associations are here defined by both, stratigraphic distribution of species and cluster analysis, ranging from the lower Eifelian to the lower Givetian. Rarefaction analysis reveals the existence of a relatively rich miospore population. Species richness increases while there is a drop in diversity and evenness towards the top of the column. The increment of the marine components towards the latter section indicates shifts in the shoreline. The influx of warmer water into higher latitudes, as highlighted by the arrival of the brachiopod Tropidoleptus, could have favored the inception of new spore species in the settled community. These results add to evidence that some groups build up the number of species in disturbed settings, and evenness is reduced with each new species introduced. © 2014 Elsevier B.V.

Cruz L.E.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Journal of South American Earth Sciences | Year: 2013

In the last twenty years, several geological and stratigraphical studies have been undertaken in Córdoba Province, and they have provided useful bases for biostratigraphic work in the late Cenozoic. However, paleontological contributions have been limited to preliminary analyses of mammal assemblages, or specific discoveries. The aim of this work is to contribute to biostratigraphic knowledge of Argentina through the study of late Cenozoic mammals from Córdoba Province. Five localities have been analyzed: San Francisco, Miramar, Río Cuarto, Isla Verde, and Valle de Traslasierra. Through biostratigraphic analysis the first records of several taxa were established, and mammal assemblages with the description and correlation of the sedimentary strata were confirmed. Finally, three Assemblage Zones (Biozonas de Asociación) were proposed: 1) Neosclerocalyptus paskoensis-Equus (Amerhippus) assemblage zone with type area and profile based on the San Francisco locality, referred to the Lujanian (late Pleistocene-early Holocene), and comparable to the Equus (Amerhippus) neogeus Biozone of Buenos Aires Province; 2) Neosclerocalyptus ornatus-Catonyx tarijensis assemblage zone with type area and profile based on the San Francisco locality, referred to the Ensenadan (early Pleistocene) and comparable to the Mesotherium cristatum Biozone of Buenos Aires Province, and 3) Nonotherium hennigi-Propanochthus bullifer assemblage zone with type area and profile based on the Los Sauces river, Valle de Traslasierra, referred to the Montehermosan-Chapadmalalan interval (Pliocene), and comparable to the Trigodon gaudryi, Neocavia depressidens and/or Paraglyptodon chapadmalensis Biozones of Buenos Aires Province. © 2012 Elsevier Ltd.

Michalik P.,University of Greifswald | Ramirez M.J.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Arthropod Structure and Development | Year: 2014

The male reproductive system and spermatozoa of spiders are known for their high structural diversity. Spider spermatozoa are flagellate and males transfer them to females in a coiled and encapsulated state using their modified pedipalps. Here, we provide a detailed overview of the present state of knowledge of the primary male reproductive system, sperm morphology and the structural diversity of seminal fluids with a focus on functional and evolutionary implications. Secondly, we conceptualized characters for the male genital system, spermiogenesis and spermatozoa for the first time based on published and new data. In total, we scored 40 characters for 129 species from 56 families representing all main spider clades. We obtained synapomorphies for several taxa including Opisthothelae, Araneomorphae, Dysderoidea, Scytodoidea, Telemidae, Linyphioidea, Mimetidae, Synotaxidae and the Divided Cribellum Clade. Furthermore, we recovered synspermia as a synapomorphy for ecribellate Haplogynae and thus propose Synspermiata as new name for this clade. We hope that these data will not only contribute to future phylogenetic studies but will also stimulate much needed evolutionary studies of reproductive systems in spiders. © 2014 Elsevier Ltd.

Grismado C.J.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Ramirez M.J.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Bulletin of the American Museum of Natural History | Year: 2013

A new genus of soft-bodied oonopids, Neotrops, is established for a large assemblage of goblin spiders found in all tropical and subtropical areas of the Neotropical region, from Panama to Uruguay and central Argentina. Members of Neotrops have spinose forelegs, and share a general palpal morphology with those of Heteroonops Dalmas, but have a prolateral conductor connected with an internal bulbal vesicle that presumably discharges its secretion through a prolateral slit. Females lack a posterior receptacle in the internal genitalia, having only a posterodorsal plate serving for muscle attachment. Here we treat all the species except those from Brazil, which will be addressed in a subsequent paper. Twenty-three new species are described: N. darwini (type species), N. lorenae, and N. sciosciae (from Argentina and Uruguay); N. yunga, N. piacentinii, N. poguazu, and N. lopardoae (from Argentina); N. rubioi, N. pombero, and N. avalosi (from Argentina and Paraguay); N. labarquei (from Uruguay), N. yabare, N. izquierdoi, and N. kopuchianae (from Bolivia); N. pithecia, N. silvae, and N. pakitza (from Peru); N. platnicki, and N. waorani (from Ecuador); N. santamarta and N. caparu (from Colombia); and N. maracay and N. amacuro (from Venezuela). Four additional species, previously placed in Oonops Templeton, are transferred here to Neotrops: O. nigromaculatus Mello-Leitão, from Argentina and Uruguay; O. tucumanus Simon, from Argentina; O. donaldi Chickering, from Panama; and O. trapellus Chickering, from Trinidad and Venezuela. The females of the three latter species are here described for the first time. Most of the species are known from the leaf litter or the foliage of tropical and subtropical forests, but also from grasslands in the southern parts of their distributional range, where they appear as the dominant soft-bodied oonopids. The relationships of this new taxon are briefly discussed, and intrageneric groupings are also proposed. © 2013 American Museum of Natural History.

Ezcurra M.D.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Journal of Systematic Palaeontology | Year: 2010

It was traditionally thought that the oldest known dinosaur assemblages were not diverse, and that their early diversification and numerical dominance over other tetrapods occurred during the latest Triassic. However, new evidence gathered from the lower levels of the Ischigualasto Fm. of Argentina challenges this view. New dinosaur remains are described from this stratigraphical unit, including the new species Chromogisaurus novasi. This taxon is distinguished from other basal dinosauriforms by the presence of proximal caudals without median notch separating the postzygapophyses, femoral lateral surface with deep and large fossa immediately below the trochanteric shelf, and metatarsal II with strongly dorsoventrally asymmetric distal condyles. A phylogenetic analysis found Chromogisaurus to lie at the base of Sauropodomorpha, as a member of Guaibasauridae, an early branch of basal sauropodomorphs composed of Guaibasaurus, Agnosphitys, Panphagia, Saturnalia and Chromogisaurus. Such an affinity is for the first time suggested for Guaibasaurus, whereas Panphagia is not recovered as the most basal sauropodomorph. Furthermore, Chromogisaurus is consistently located as more closely related to Saturnalia than to any other dinosaur. Thus, the Saturnalia + Chromogisaurus clade is named here as the new subfamily Saturnaliinae. In addition, Eoraptor is found to be the sister-taxon of Neotheropoda, and herrerasaurids to be non-eusaurischian saurischians. The new evidence presented here demonstrates that dinosaurs first appeared in the fossil record as a diverse group, although they were a numerically minor component of faunas in which they occur. Accordingly, the early increase of dinosaur diversity and their numerical dominance over other terrestrial tetrapods were diachronous processes, with the latter preceded by a period of low abundance but high diversity.© 2010 The Natural History Museum.

Palazzesi L.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Barreda V.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Nature Communications | Year: 2012

The timing of major turnovers in terrestrial ecosystems of the Cenozoic Era has been largely interpreted from the analysis of the assumed feeding preference of extinct mammals. For example, the expansion of open-habitat ecosystems (grasslands or savannas) is inferred to have occurred earlier in Patagonia than elsewhere because of the early advent of high-crowned teeth (hypsodont) mammals ∼26 Ma ago. However, the plant fossil record from Patagonia implies another evolutionary scenario. Here we show that the dominance of key open-habitat species - amaranths, Ephedra, asters and grasses - occurred during the last 10 Ma, about 15 Ma later than previously inferred using feeding/habitat ecology of extinct mammals. This late rise of open-landscapes in southern South America brings into question whether the expansion of open-habitat vegetation could have been the prime factor of high-crowned mammal diversification. © 2012 Macmillan Publishers Limited. All rights reserved.

Prevosti F.J.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Cladistics | Year: 2010

South America currently possesses a high diversity of canids, comprising mainly small to medium-sized omnivorous species, but in the Pleistocene there were large hypercarnivorous taxa that were assigned to Protocyon spp., Theriodictis spp., Canis gezi, Canis nehringi and Canis dirus. These fossils have never been included in phylogenies based on quantitative cladistics, but hand-constructed cladograms published in the 1980s included some of them in the South American canine clade and others in the Canis clade. In this work, the phylogenetic position of the large extinct South American canids was studied using a large sample of living and extinct canids, as well as different sources of characters (e.g. DNA and 133 osteological characters). The phylogenetic analysis corroborates the inclusion of Theriodictis and Protocyon in the " South American clade" , where C. gezi is also included. In addition, the position of C. dirus as a highly derived Canis species is confirmed. The simultaneous analysis supports hypercarnivory having arisen at least three times in Caninae and once in the " South American clade" The combination of the phylogenetic analyses, the fossil record and divergence dates estimated in previous works suggests that at least three or four independent lineages of the " South American clade" invaded South America after the establishment of the Panama bridge around 3 million years ago, plus other events corresponding to the immigration of Urocyon and Canis dirus.© The Willi Hennig Society 2009. © The Willi Hennig Society 2009.

Ezcurra M.D.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Agnolin F.L.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Agnolin F.L.,Maimónides University
Systematic Biology | Year: 2012

Late Mesozoic palaeobiogeography has been characterized by a distinction between the northern territories of Laurasia and the southern landmasses of Gondwana. The repeated discovery of Gondwanan lineages in Laurasia has led to the proposal of alternative scenarios to explain these anomalous occurrences. A new biogeographical model for late Mesozoic terrestrial ecosystems is here proposed in which Europe and Gondwanan territories possessed a common Eurogondwanan fauna during the earliest Cretaceous. Subsequently, following the Hauterivian, the European territories severed from Africa and then connected to Asiamerica resulting in a faunal interchange. This model explains the presence of Gondwanan taxa in Laurasia and the absence of Laurasian forms in the southern territories during the Cretaceous. In order to test this new palaeobiogeographical model, tree reconciliation analyses (TRAs) were performed based on biogeographical signals provided by a supertree of late Mesozoic archosaurs. The TRAs found significant evidence for the presence of an earliest Cretaceous Eurogondwanan fauna followed by a relatively short-term Gondwana-Laurasia dichotomy. The analysis recovered evidence for a biogeographical reconnection of the European territories with Africa and South America-Antarctica during the Campanian to Maastrichtian time-slice. This biogeographical scenario appears to continue through the early Tertiary and sheds light on the trans-Atlantic disjunct distributions of several extant plant and animal groups. © 2012 The Author(s).

Martinez L.C.A.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Review of Palaeobotany and Palynology | Year: 2010

A new genus and species of fossil wood with Leguminosae (Mimosoideae) affinities from the Late Miocene Chiquimil Formation (Santa María Group) in Catamarca Province, Argentina, is described. Prosopisinoxylon anciborae Martínez lacks growth rings, is diffuse porous, has vessels of two distinct diameters, simple perforation plates, alternate and vestured intervessel pits, rays commonly 1 to 9 seriate and confluent axial parenchyma with prismatic crystals in chambered diffuse paratracheal parenchyma cells. This taxon has the greatest similarity to extant genus Prosopis L. Based on the presence of Prosopis fossil leaves and pollen in the Miocene San José and Morterito formations, Argentina, the genus expands its distribution in the past, showing that Prosopis was an important element of Miocene floras of northwestern Argentina and would explain its high extant diversity. © 2009 Elsevier B.V. All rights reserved.

Kuppers G.C.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia
European Journal of Protistology | Year: 2014

The present work describes the morphology and infraciliature of a new hypotrichous ciliate, Clapsiella magnifica gen. n., sp. n., found in rewetted soil from a temporal pond in Argentina. It was studied by means of live observation and protargol impregnation. Its main diagnostic features are: Flexible hypotrich measuring 250-320. μm. ×. 70-140. μm in vivo; two macronuclear nodules and 4-6 micronuclei. Single contractile vacuole. Cytoplasm transparent, cortical granules absent. Somatic ciliature composed of a tricorona of cirri, three buccal(?) cirri, 6-9 ventral rows, 3-5 right marginal(?) rows, one left marginal row, and 12-17 transverse cirri. Dorsal pattern rather complicated, with about 14 kineties and kinety fragments, with scattered kinetids among them; 17-28 caudal cirri arranged in three rows on dorsal kineties 1, 3, and 7. Remarkably, dorsal kinetids have two or four basal bodies, bearing a stiff bristle arising from left anterior basal body. Adoral zone composed of 70-92 membranelles, occupying about 40% of body length in protargol preparations; paroral and endoral curved, resembling a cyrtohymenid pattern. The peculiar dorsal ciliary arrangement and the unique combination of other characters require the establishment of a new genus for this new species, which is considered incertae sedis in the Hypotricha but possibly related to the oxytrichids. © 2014 Elsevier GmbH.

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