Museo Nacional de Historia Natural

Montevideo, Uruguay

Museo Nacional de Historia Natural

Montevideo, Uruguay
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Rinderknecht A.,Museo Nacional de Historia Natural | Bostelmann E.,Austral University of Chile
Journal of Systematic Palaeontology | Year: 2017

South American giant fossil rodents represent a notable example of an extreme evolutionary trend towards size differentiation among caviomorph lineages. Although spectacular, fossil remains of these animals are uncommon and usually highly incomplete. We here describe fully grown adult and juvenile fossil specimens from the rodent family Dinomyidae Alston, 1876, collected from the same location, lithostratigraphical formation and fossiliferous horizon: the coast of the Río de la Plata of southern Uruguay in pelitic sediments assigned to the late Miocene Camacho Formation. The adult remains consist of an almost complete skull with partial jaw and represent the first published description of associated craneo-mandibular remains of a giant rodent within the subfamily Eumegamyinae. The juvenile specimen is the first to be recognized as such for the entire subfamily, and consists of a complete mandible and a right calcaneus. Based on the homologies observed in the configuration of the teeth, the new specimens are assigned to Isostylomys laurillardi Kraglievich, 1926, thus demonstrating that the general morphology of the teeth (including the binding pattern) of Eumegamyinae remained unchanged throughout most of their growth. The dental ontogeny of large-sized rodents casts doubt on the validity of the subfamily Gyriabrinae, which may be composed of juveniles of different taxa within other subfamilies of Dinomyidae. © The Trustees of the Natural History Museum, London 2017. All rights reserved.

Rinderknecht A.,Museo Nacional de Historia Natural
Journal of Mammalian Evolution | Year: 2017

The fossil record of carnivorous mammals in Uruguay is scarce and fragmentary, but informative. In the present contribution, two new records of canids allocated in sediments of the Dolores Formation (late Pleistocene-early Holocene) are described. These records, based on their anatomical-comparative study and multivariate analysis, correspond to two foxes: one of medium size, Cerdocyon thous, conforms to the first record of this taxon in the country, meanwhile the other one, of larger size, is referred to Dusicyon avus and is the first fossil record of this animal in the south of the territory and the second record in the whole country. Until now, the only carnivorous mammals registered in this formation were the hunters of large herbivores (Arctotherium sp. and Smilodon populator). In this way, these discoveries complement and expand the set of placental mammals with a carnivorous diet for this unit, particularly with the capacity to predate over small- and medium-size mammals. © 2017 Springer Science+Business Media New York

Blanco R.E.,Institute Fisica | Rinderknecht A.,Museo Nacional de Historia Natural | Lecuona G.,Museo Nacional de Historia Natural
Lethaia | Year: 2012

An exceptionally well-preserved skull of the largest fossil rodent Josephoartigasia monesi allows the first analysis of the bite mechanics of this group of South American giant rodents. In this study, we reconstructed the main anatomical features of the skull of this Pliocene rodent, relating them to the bite force at incisors. Bite force was estimated using three different techniques. Two methods suggest that bite forces at incisors of around 1000 N were possible for these mammals. However, the incisors seem to be stronger than expected for this bite force implying that the bite forces may have been greater than 3000 N. We consider three hypotheses: allometric effects, teeth digging or defence against predators, to explain our results. © 2011 The Authors, Lethaia © 2011 The Lethaia Foundation.

Rinderknecht A.,Museo Nacional de Historia Natural | Bostelmann T. E.,Museo Nacional de Historia Natural
Journal of Mammalogy | Year: 2011

In this contribution we describe the fossil remains of a new genus and species of a giant rodent, Arazamys castiglionii (Mammalia, Rodentia, Dinomyidae), from Arazatí beach in San José Department, southern Uruguay. The specimen was exhumed from pelitic sediments of the Camacho Formation, biostratigraphically assigned to the late Miocene Huayquerian South American Land Mammal Age. The remains include an incomplete skull (braincase, auditory region, and nearly full dentition) and the atlas. Based on comparative studies of the anatomy of the auditory region, we describe 2 morphologies for the subfamily Eumegamyinae, 1 characterized by a short meatus acusticus externus, a great development of the foramen stylomastoideum, and a conspicuous ectotympanic cavity, and a 2nd characterized by a long meatus acusticus externus and lack of the ectotympanic fossa. The potential taxonomic and systematic value of the auditory region in Dinomyidae is discussed. © 2011 American Society of Mammalogists.

Parham J.F.,California State University, Fullerton | Papenfuss T.J.,University of California at Berkeley | Dijk P.P.V.,Wildlife Conservation Society | Wilson B.S.,University of the West Indies | And 3 more authors.
Molecular Phylogenetics and Evolution | Year: 2013

Determining whether a conflict between gene trees and species trees represents incomplete lineage sorting (ILS) or hybridization involving native and/or invasive species has implications for reconstructing evolutionary relationships and guiding conservation decisions. Among vertebrates, turtles represent an exceptional case for exploring these issues because of the propensity for even distantly related lineages to hybridize. In this study we investigate a group of freshwater turtles (Trachemys) from a part of its range (the Greater Antilles) where it is purported to have undergone reticulation events from both natural and anthropogenic processes. We sequenced mtDNA for 83 samples, sequenced three nuDNA markers for 45 samples, and cloned 29 polymorphic sequences, to identify species boundaries, hybridization, and intergrade zones for Antillean Trachemys and nearby mainland populations. Initial coalescent analyses of phased nuclear alleles (using *BEAST) recovered a Bayesian species tree that strongly conflicted with the mtDNA phylogeny and traditional taxonomy, and appeared to be confounded by hybridization. Therefore, we undertook exploratory phylogenetic analyses of mismatched alleles from the " coestimated" gene trees (Heled and Drummond, 2010) in order to identify potential hybrid origins. The geography, morphology, and sampling context of most samples with potential introgressed alleles suggest hybridization over ILS. We identify contact zones between different species on Jamaica (T. decussata×T. terrapen), on Hispaniola (T. decorata×T. stejnegeri), and in Central America (T. emolli×T. venusta). We are unable to determine whether the distribution of T. decussata on Jamaica is natural or the result of prehistoric introduction by Native Americans. This uncertainty means that the conservation status of the Jamaican T. decussata populations and contact zone with T. terrapen are unresolved. Human-mediated dispersal events were more conclusively implicated for the prehistoric translocation of T. stejnegeri between Puerto Rico and Hispaniola, as well as the more recent genetic pollution of native species by an invasive pet turtle native to the USA (T. scripta elegans). Finally, we test the impact of introgressed alleles using the multispecies coalescent in a Bayesian framework and show that studies that do not phase heterozygote sequences of hybrid individuals may recover the correct species tree, but overall support for clades that include hybrid individuals may be reduced. © 2013 Elsevier Inc.

Otero R.A.,Museo Paleontologico de Caldera | Soto-Acuna S.,University of Chile | Rubilar-Rogers D.,Museo Nacional de Historia Natural
Acta Palaeontologica Polonica | Year: 2010

The revision by Hiller et al. (2005) of the species Mauisaurus haasti Hector (Plesiosauroidea, Elasmosauridae) from the Late Cretaceous of New Zealand, has provided reliable postcranial characters that permit recognition of this taxon as distinct among Late Cretaceous elasmosaurid plesiosaurs from both the Northern and Southern hemispheres. Particularly, in adult specimens, the femur displays a large, hemispherical capitulum that seems to be autapomorphic. This unique morphology is present in at least two specimens recovered from Late Cretaceous (Maastrichtian) beds in central Chile, which these fossils may be referred to the same taxon with confidence. The Chilean fossils are considerably larger than those from New Zealand, suggesting either difference in ontogenetic age or interspecific variation. The studied material constitutes the second accurate generic identification of elasmosaurid plesiosaurs from the eastern margin of the Pacific Ocean, thus complementing the known south-gondwanic paleodistribution of Mauisaurus during the Late Cretaceous.

Pujos F.,CONICET | Pujos F.,Institute Francais dEtudes Andines | De Iuliis G.,University of Toronto | De Iuliis G.,Royal Ontario Museum | Quispe B.M.,Museo Nacional de Historia Natural
Journal of Vertebrate Paleontology | Year: 2011

A dentary from the Laventan SALMA (middle Miocene) of Quebrada Honda, Bolivia, recognized as a new, small member of Megatherioidea (Hiskatherium saintandrei, gen. et sp. nov.), is reported. This taxon is clearly distinct from Nothrotheriidae and Megalonychidae and has affinities with Hapalops and Xyophorus. It is characterized by m1-m4 without diastema; strong hypsodonty (HI = 0.93); m1-m3 constituted by two transverse lophids separated by a deep, transverse, and labially open valley; m4 round with distal lophid mesiolingually-distolabially extended and without vertical groove; m2-m3 with lingual and labial vertical grooves; and the posteroventral margin of symphysis located anteriorly to m1. Although Hiskatherium and Diabolotherium have a similar dental formula, the 'megatheriine-shaped' teeth of Diabolotherium do not support a close phylogenetic relationship between Hiskatherium and Diabolotherium. Their dental formulae suggest that both genera were selective feeders, capable of consuming tough items. Hiskatherium, like most other sloths, has lower molariform teeth that have a mesial and a distal lophid; the former has a mesial cuspid 'A,' located at the center of the mesial lophid, and the latter has distolingual ('B,' or lingual) and distolabial ('C') cuspids at each end. This terminology permits a straightforward nomenclature based on cusp/cuspid position and facilitates comparisons among Tardigrada. © 2011 by the Society of Vertebrate Paleontology.

A new genus and 13 new species of Scaphopoda (ten Dentaliida and three Gadilida) are described from the tropical Pacific Ocean in the Coral Sea, Solomon Islands, Vanuatu, Fiji, Wallis Island and Tonga. Th e new genus is named Boissevainia n. gen. and the new species are Paradentalium choneides n. sp., P. danielleae n. sp., Fustiaria electra n. sp., F. diaphana n. sp., Gadilina lauensis n. sp., Episiphon joanae n. sp., E. wallisi n. sp., E. indefensum n. sp., E. kantori n. sp., E. lacteum n. sp. (Dentaliida); Bathoxiphus kathieae n. sp., Annulipusellum aenigmaticum n. sp. and Boissevainia mossiae n. gen., n. sp. (Gadilida). Th e new taxa not only highlight the diversity of the class in the tropical Pacific Ocean, but also indicate the presence of morphologies not yet recorded for the region or described for the class. © Publications Scientifiques du Muséum national d'Histoire naturelle, Paris.

Mayr G.,Senckenberg Institute | Rubilar-Rogers D.,Museo Nacional de Historia Natural
Journal of Vertebrate Paleontology | Year: 2010

Bony-toothed birds (Pelagornithidae) were among the largest volant birds, but their representatives from the upper size range have so far been known only from very fragmentary fossils. Here we report an exceptionally well-preserved giant species from the late Miocene of the Baha Inglesa Formation in northern Chile, in which most major limb bones are complete and uncrushed. The fossil has the longest wing skeleton of any bird, and its wingspan in life was at least 5.2 m. Mass estimates of 1629 kg are, however, surprisingly low and within the range of large extant volant birds, or only moderately above. The fossil constitutes the most substantial record of the Pelagornithidae (bony-toothed birds), and is assigned to a new species, Pelagornis chilensis. It is one of the largest known pelagornithids and the three-dimensionally preserved bones allow recognition of many previously unknown osteological features, especially concerning the vertebrae, pectoral girdle, and limb elements. We revise the taxonomy of Neogene pelagornithids and propose classification of all Miocene and Pliocene species into a single genus, Pelagornis. Osteological features are highlighted in which giant Neogene Pelagornithidae differ from their smaller Palaeogene relatives. © 2010 by the Society of Vertebrate Paleontology.

Esquerre D.,Museo Nacional de Historia Natural | Nunez H.,Museo Nacional de Historia Natural | Scolaro J.A.,CONICET
Zootaxa | Year: 2013

Most of the lizards of the Liolaemus genus present precloacal pores in males, with few exceptions in species of the lineomaculatus and neuquensis groups, and in the elongatus-kriegi complex. The elongatus-kriegi complex, belonging to the Liolaemus (sensu stricto) subgenus, is composed of medium sized, saxicolous, viviparous and insectivorous or omnivorous lizards, distributed between the Andean and Patagonian zones of Chile and Argentina. We reviewed the taxonomic history of this group, and we describe two new species, Liolaemus carlosgarini, found in the vicinity of the Maule Lagoon, in the Maule Region, Chile, and Liolaemus riodamas, described from the population that was originally designated as Liolaemus cf. ceii, from Las Damas River, near the Termas del Flaco locality, in the Libertador Bernardo O'Higgins Region, thereby based on this research L. ceii is eliminated from the species belonging to Chile. Both species have as a diagnostic character the absence of precloacal pores, and we suggest here their presumptive systematic relationships in Liolaemus. We analyzed ten species of Liolaemus, in order to perform a phylogenetic analysis based on external morphology, using mostly squamation and morphometric characters. The analysis was performed using PAUP, with the Maximum Parsimony criterion. In addition, through diaphanisation, we studied and described the osteology of the new species. We conclude that species lacking precloacal pores do not form a monophyletic group, and that constructing a phylogeny using only external morphology, at least for this group of reptiles, is insufficient to establish solid phyletic relationships. Other sort of characters should complement the morphological ones. Copyright © 2013 Magnolia Press.

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