Museo de La Plata

La Plata, Argentina

Museo de La Plata

La Plata, Argentina

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Figueirido B.,University of Malaga | Soibelzon L.H.,Museo de La Plata
Lethaia | Year: 2010

In this study we explore the ecomorphological patterns of extinct tremarctine bears in South America during the Great American Biotic Interchange (GABI). These patterns are used to derive palaeoautoecological inferences in extinct tremarctines and their palaeosinecological relationships within Plio-Pleistocene ecosystems. We used geometric morphometrics of landmark data to recover the shape of the craniomandibular skeleton of bears. The results reveal different ecomorphological specializations in extinct tremarctines during the Plio-Pleistocene of South America. Indeed, these bears could have increased the percentage of plant matter in their diets according with the increased diversity of large carnivores in South America after the GABI. Omnivorous bears retain the ability to behave as carnivores or herbivores depending on resource availability. This fact strongly supports that bears are one of the most ecologically and morphologically adaptable members of the large carnivore guild. Moreover, their skull morphology could reflect ecological adaptations under different selection pressures with the required evolutionary time. □. Evolution, GABI, geometric morphometrics, palaeoecology, Tremarctinae. © 2009 The Authors, Journal compilation © 2009 The Lethaia Foundation.


Zamorano M.,Museo de La Plata | Brandoni D.,CONICET
Alcheringa | Year: 2013

To test the monophyly of Panochthini, a phylogenetic analysis including all the species traditionally referred to the tribe was conducted. The matrix included 16 species of Glyptodontidae and 35 characters, from which 14 correspond to the skull, four to the dentition, two to the cephalic armour, nine to the dorsal carapace and six to the caudal sheath. Propalaehoplophorus australis (Propalaehoplophorinae) was used to root the trees. Four most parsimonious trees were obtained (Tree Length = 75, CI = 0.65, RI = 0.70). The strict consensus tree (Tree Length = 77, CI = 0.64, RI = 0.68) has the following topology: Propalaehoplophorus australis (Glyptodon reticulatus (Hoplophorus euphractus (Panochthus jaguaribensis, P. intermedius (P. frenzelianus, P. tuberculatus (P. subintemedius, P. greslebini)))) ((Pseudoplohophorus absolutus, Plohophorus figuratus) (Nopachtus cabrerai, N. coagmentatus, Propanochthus bullifer, Stromaphorus compressidens, Phlyctaenopyga ameghini))). The results indicate that: 1, Panochthini is not a natural group but polyphyletic; 2, Panochthus is monophyletic and, concordant with recent proposals, Hoplophorus euphractus is its sister group; and 3, Nopachtus and Propanochthus are more closely related to species traditionally referred to 'Plohophorini' than to Panochthus. Nopachtus and Propanochthus, as the 'Plohophorini', are recorded from the latest part of the Neogene, whereas Panochthus and Hoplophorus euphractus are restricted to the Quaternary. © 2013 Association of Australasian Palaeontologists.


Perez M.E.,Museo Paleontologico Egidio Feruglio | Vucetich M.G.,Museo de La Plata
Journal of Mammalian Evolution | Year: 2011

The family Caviidae is represented in modern faunas by cavies and maras, whereas the family Hydrochoeridae is represented by capybaras. The evolutionary origin of these families has been related to a diversity of plesiomorphic fossil forms (recorded from the late Oligocene up to the middle Miocene) traditionally grouped in the family "Eocardiidae". These fossil forms were included, together with Caviidae and Hydrochoeridae, within the Cavioidea s. s. (sensu stricto), because they share high crowned cheek teeth, double-hearted occlusal surface, short lower incisors, and moderate hystricognathy. Within Cavioidea s. s., caviids and hydrochoerids were interpreted as forming its crown group, because they have unique craniomandibular and dental features. In this contribution, a new taxon of Cavioidea s. s. from the middle Miocene of central Patagonia, Argentina, is described, and its phylogenetic position is determined on the basis of a morphological cladistic analysis in which "eocardiids" were included. The study permits the understanding of the sequence of appearance of characters that originated the highly divergent morphology of crown-group cavioids. The analysis of the sequence of appearance of the characters that traditionally diagnosed the crown group indicates that these changes did not occur at the same time. On the contrary, many of these features seem to have appeared at different nodes of the evolutionary history of Cavioidea s. s. The remarkably derived morphology of modern cavioids is the result of a stepwise appearance of a mosaic of evolutionary innovations that originated gradually along the history of Cavioidea during the late-middle Miocene. © 2011 Springer Science+Business Media, LLC.


Fernandez M.S.,Museo de la Plata | Talevi M.,National University of Rio Negro
Geological Magazine | Year: 2014

The oldest ophthalmosaurian records worldwide have been recovered from the Aalenian-Bajocian boundary of the Neuquén Basin in Central-West Argentina (Mendoza and Neuquén provinces). Although scarce, they document a poorly known period in the evolutionary history of parvipelvian ichthyosaurs. In this contribution we present updated information on these fossils, including a phylogenetic analysis, and a redescription of 'Stenopterygius grandis' Cabrera, 1939. Patagonian ichthyosaur occurrences indicate that during the Bajocian the Neuquén Basin palaeogulf, on the southern margins of the Palaeopacific Ocean, was inhabited by at least three morphologically discrete taxa: the slender Stenopterygius cayi, robust ophthalmosaurian Mollesaurus periallus and another indeterminate ichthyosaurian. Rib bone tissue structure indicates that rib cages of Bajocian ichthyosaurs included forms with dense rib microstructure (Mollesaurus) and forms with an 'osteoporotic-like' pattern (Stenopterygius cayi). Copyright © Cambridge University Press 2013.


During the Mesozoic, one of the most significant evolutionary processes was the secondary adaptation of tetrapods to life in water. Several non-related lineages invaded from the terrestrial realms and from the oceans of the entire world. Among these lineages, ichthyosaurs were particularly successful. Advance parvipelvian ichthyosaurs were the first tetrapods to evolve a fish-shaped body profile. The deep skeletal modifications of their bodies, as well as their biology, depict advance ichthyosaurs as the paradigm of secondary adaptation of reptiles tomarine life. Functional inferences point to themas off-shore cruising forms, similar to a living tuna, and some of them were capable of deep diving. Bone histology of some genera such as Temnodontosaurus, Stenopterygius, Ichthyosaurus, and Caypullisaurus, characterized by overall cancellous bone, is consistent with the idea of a fish-shaped ichthyosaurs as fast and far cruisers. Here, we provide histological examination of the ribs of the Middle Jurassic parvipelvian Mollesaurus. Contrasting with the bone histology of other parvipelvian, Mollesaurus ribs are characterized by a compact and thick cortex. Our data indicate that the rib cage was heavy and suggest that not all advanced ichthyosaurs were fast cruisers. The compact and dense ribs in these parvipelvian show that advance ichthyosaurs were ecologically more diverse than previously thought and that the lightening of the skeleton reversed, as also occurred in the evolution of cetacean, at least once along the evolutionary history of ichthyosaurs. © Springer-Verlag 2012.


Lichenodraculus matti gen. et sp. nov. is described, along with its conspicuous diurnal calling song and some aspects of its interesting ecology and life history. The song allowed a complete acoustic assessment of the altitudinal distribution of this otherwise very cryptic canopy-dwelling insect. The nymph perfectly mimics epiphytic lichens growing in the same elevation range, and apparently the downside of this camouflage is a strictly lichenous diet. Copyright © 2011 · Magnolia Press.


Three new thyasirid species from the Sub-Antarctic and Antarctic waters are described: Thyasira patagonica, Mendicula sudamericana, and Axinulus antarcticus. T. patagonica is characterized by its strong commarginal sculpture, shell as height as length or higher than long, posterior auricle delimited by a deep submarginal sulcus, and a long and sloping straight anterior half of dorsal margin. M. sudamericana distinguished by its longer than high shell outline, elongated tooth-like enlargement anterior to beak, gills with only one demibranch at each side, and foot with a marked heel. A. antarcticus has a minute, subquadrate shell, hinge with a small swelling anterior to beak, gills with a single demibranch, and the lateral body pouch elongated and almost smooth. The present study provides the first reliable record of thyasirids, with a single demibranch from the Southern Ocean. Moreover, characters for a better definition of Mendicula are provided. © 2009 Springer-Verlag.


Picasso M.B.J.,Museo de La Plata
Journal of Zoology | Year: 2012

The greater rhea (Rhea americana) is the largest flightless bird of South America and has a cursorial locomotion style. The objective of this study was to explore how the leg configuration of this species changes from juveniles to adult, and the possible implications of these changes for the locomotor style of this bird. In this regard, it is interesting to study the presence of allometries during growth (ontogenetic allometry), because it may provide information about morpho-functional aspects. Growth of femur, tibiotarsus and tarsometatarsus were studied in individuals of different ages, ranging from 1 month to adulthood. Allometric analysis was performed on a total of 21 measurements of limb bones to evaluate ontogenetic changes. Ten measurements were allometric, correlating positively and negatively with body mass. Some of them, like the positive allometry of the tarsometatarsus length, the negative allometry of the distal region of the tibiotarsus and the proximal segment of the tarsometatarsus, seem to be associated with cursoriality. On the other hand, the positive allometric growth of the distal segment of the femur may be related to the large body size of these birds. © 2011 The Author. Journal of Zoology © 2011 The Zoological Society of London.


Candela A.M.,Museo de La Plata | Rasia L.L.,Museo de La Plata
Zoological Journal of the Linnean Society | Year: 2012

Echimyidae constitute the most important radiation of caviomorph rodents in the Neotropical region, represented by 20 extant genera and several extinct species. Both in extant and fossil forms, this diversity is reflected by a significant morphological variation found in crown structures of the cheek teeth. Different hypotheses of primary homology have been proposed for these structures, which, in turn, support diverse dental evolutionary hypotheses. In this contribution we inspect the main structures (cusps and lophids) of the lower deciduous teeth and molars in extinct and extant Echimyidae, and establish their topological correspondences. Comparisons with cusps and lophids of Erethizontidae are emphasized. We explore the testing of alternative primary hypotheses of lophid correspondences in a cladistic context. Following a 'dynamic' approach, we select the hypothesis of primary homology, which produced the more parsimonious results, and evaluate the evolutionary transformations of the dental characters analysed. In this context, the phylogenetic relationships of living Myocastor coypus (Molina, 1782) with the extinct Tramyocastor and Paramyocastor are tested. Our results indicate that pentalophodonty is the derived condition for the lower molars in Echimyidae, that trilophodonty evolved independently at least three times during the evolutionary history of these rodents, and that tetralophodonty represents the plesiomorphic condition. This study shows that dental evolution in echimyids can be better understood when occlusal structures are expressed as reliably comparable characters, and when fossils are taken into account. © 2012 The Linnean Society of London.


The main purpose of this paper is the description of two very tiny, long-legged, and short-winged katydids from the eastern slope of the eastern Andean cordillera of south-east Ecuador, Nanoleptopoda nigrifrons gen. et sp. nov. and N. albifrons sp. nov., the first species along with its ultrasound calling song. The monospecific and closely-related genus Parangara is included in Odonturini. Dichopetala inca and Anisophya equatorialis are transferred under the so far monospecific genus Cohnia, so that now the tribe includes three genera with six species from the tropical Andes. The ecological background of wing reduction in relation to elevation is briefly discussed.

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