Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Coccolithophore thanatocoenosis from 33 surface sediment samples in the Argentina Continental Margin were analyzed. Emiliania huxleyi, the most ubiquitous species in today´s ocean, occurs at relative abundances higher than 60% and tends to obscure the variations in abundance of less represented species. This study aims to compare two intensively used counting methods in coccolithophore studies: including and excluding E. huxleyi from the data set and compare which of both methodologies better reflects the known oceanographic conditions in the area. In the two data sets, species abundances were converted to percentages and Clusters Analysis were performed. The result including E. huxleyi reveals two groups (A and B) separated of compositional Euclidean distance of 12.8. Group A is restricted to the southeastern area (near Malvinas Islands) and is dominated by Gephyrocapsa muellerae (> 56%). Group B is dominated by E. huxleyi (> 93%) and is distributed into two areas: in the southwest (near Tierra del Fuego) and in the north (between 40°S – 47°S). The result excluding E. huxleyi also shows two groups (A’ and B’) distant to a compositional Euclidean distance of 15.8. Group A’ has both a southern and northern distribution, whereas Group B’ is present only at the northern area. These two groups cannot be explained by the relation between the coccolithophore taxa dominance and the surface oceanographic conditions. Our results indicate that the inclusion of E. huxleyi is the most appropriate approach since it seems to better correlate with the known oceanographic regime in the Argentina Continental Margin.

During the Pleistocene, South America had several genera and species of large hypercarnivorous canids, which became completely extinct at the end of this epoch. This paper presents a comprehensive systematic review of the group (four genera, seven species) based on new cladistic analyses that include genomic information and a study of intraspecific variation in canids. The results generated are discussed in the context of knowledge on the phylogeny, systematics, biostratigraphy, paleoecology, and biogeography of South American canids. Protocyon orcesi was synonymized with Protocyon troglodytes, and Canis nehringi with Aenocyon dirus. The genus Theriodictis would be paraphyletic, so T. tarijensis was transferred to Protocyon. “Canis” gezi does not belong to the genus Canis. The distribution of A. dirus and P. troglodytes would reach the Pampean Region and the latter as far as Mexico. On the other hand, the distribution of Theriodictis was restricted to the Pampean Region. The fragmentary nature of several taxa from North and South America complicates their phylogenetic location and biogeographical and evolutionary interpretations. However, several immigration events from North and Central America, and some later ones in the opposite direction, can be inferred, and a diversification in South America. New specimens with good preservation are needed to evaluate the presence of Chrysocyon and Theriodictis outside South America and the assignment of several canids from the Orocual sites (Venezuela). The available evidence does not allow us to corroborate the presence of large canids prior to the Ensenadense (>1.8 Ma).

New records of mammals from the Late Pleistocene of the province of Entre Ríos are presented in this contribution. The fossils come from the Salto Ander Egg Formation, a unit which is deposited in the fluvial valleys of the southwest of Entre Ríos and dated between 120 ka and 60 ka by OSL. It is interpreted that the formation sequences were accumulated during MIS 5. The paleontological content of the unit constitutes the record that best characterizes the beginning of the Late Pleistocene for South America and the MIS 5e-MIS 5c transition. In this work 12 taxa are described: cf. Ozotoceros bezoarticus (Cervidae), Morenelaphus cf. brachyceros (Cervidae), Hemiauchenia paradoxa (Camelidae), Lama guanicoe (Camelidae), Mylodon darwini (Mylodontidae), Glossotherium robustum (Mylodontidae), Lestodon armatus (Mylodontidae), Glyptodon reticulatus (Glyptodontidae), Panochthus tuberculatus (Glyptodontidae), Eutatus seguini (Dasypodidae), Notiomastodon platensis (Gomphotheriidae), and Toxodon platensis (Toxodontidae). Most of them are new records and are more complete specimens than those previously known for the unit. Mylodon darwini represents the first record for the Salto Ander Egg Formation, extending its geographic distribution in the province widely. In addition, a new fossiliferous locality corresponding to Arroyo El Bellaco (Diamante Department) is revealed and the number of records from the Arroyo El Pelado site, which until now was known for only three finds, increases notably.

“The present state of knowledge of the Cenozoic birds of Argentina” published in Contributions in Sciences in 1980, written by the argentine paleontologist Eduardo Pedro Tonni, became a must-read for those interested in the record of fossil birds. In that work, all the records known up to that time are compiled and some comments are made. Since then, there have been crucial advances in unraveling the diversity of Cenozoic birds in Argentina. Based on that work, here is a detailed updated and annotated list of all known avian records in Argentina that includes representatives of Palaeognathae (Tinamiformes and Rheiformes), Galloanseres (Anseriformes) and Neoaves (Sphenisciformes, Suliformes, Charadriiformes, Phoenicopteriformes, “Ciconiiformes”, “Gruiformes”, Pelecaniformes, Coraciimorphae, Cathartiformes, Accipitriformes, Falconiformes, Cariamiformes and Passeriformes). Besides, a substantial contribution is that here are photographs of the holotypes of all the new species that were nominated after Tonni's work and a table that compiles the main bibliographic information referring to the systematic history of each taxon.

The contemporary mammalian communities of South America were defined by the rise of the Isthmus of Panama and by the deep climatic oscillations during the Pleistocene. Horses are a conspicuous group of North American immigrant mammals that came to South America during the late Pliocene and did not survive the great megafauna extinction approximately twelve thousand years ago. The present study compiles updated data on the phylogeny, systematics and ecology of this group in South America. The first lineage is represented by the genus Equus, which appears in the Middle Pleistocene and presents anatomical features similar to those of a current horse. The second lineage is the species included in the genus Hippidion, which were horses with highly distinctive anatomical features that were first recorded in the late Pliocene. Both genera of horses include small (H. devillei, H. saldiasi, E. andium and E. insulatus) and large (E. neogeus and H. principale) forms, which dispersed in South America using two different routes. The possible model for this dispersal indicates that the small forms used the corridor of the Andes, while the larger horses dispersed along the eastern route and some coastal areas.

The qualitative and quantitative taxonomic composition of the micromammal assemblages (including didelphimorphs, chiropterans, and rodents) derived from trophic activity of strigiform birds is analyzed. The studied samples have been collected in the coastal locality of Centinela del Mar (38° 26’ 18.56” S; 58° 13’ 17.42” W, General Alvarado, Buenos Aires, Argentina) and they are staggered, chronologically, to represent the last 500 years (i.e., Late Holocene–Antropocene). From those older is registered the local or regional extinction of six species of rodents (i.e., Bibimys torresi, Ctenomys sp., Eligmodontia typus, Necromys lasiurus, Phyllotis sp. and Pseudoryzomys simplex) and the biological extinction of one chiropteran (Desmodus draculae). In the most recent samples is verified a dramatic increase in the rodent Calomys sp. The current micromammal community was shaped by the anthropic impact, especially the agricultural activities of the last century, acting on an impoverished pool of species due to global climate events during the Late Holocene (e.g., Medieval Warm Epoch, Little Ice Age). The previous reference of these types of assemblages as no-analog is discussed, being characterized by the sympatric occurrence of taxa currently allopatric.

A brief revision of selected studies on the Quaternary continental vertebrates of Uruguay is provided. The diversity of the dominant group in the record—mammals—was notably increased as well as in some avian groups. The temporal framework takes into account the chronostratigraphic proposal available for the Pampean region as a biostratigraphic correlation tool and an increasing number of numerical ages (radiocarbon and optically stimulated luminescence). The sedimentary beds outcropping in northern Uruguay (the sopas Formation) yield a rich and diverse fossil content. They are correlated to the Lujanian stage/Age and the numerical ages of many outcrops fall in the range of the Marine Isotopic stage 3 (MIs 3). The vertebrates support diverse environments including freshwater bodies, riparian forests, semi-open forests, open areas, and semiarid to arid local environments. In southern Uruguay, the Dolores Formation is correlated to the Lujanian and the numerical ages are mostly related to the last glacial maximum and Early Holocene. Aridity and semiaridity conditions facilitated by cold temperatures in the Last Glacial Maximum explain the record of some mammals living today in arid contexts or higher latitudes of south America. In coastal ravines of the Río de la Plata (southwestern Uruguay) outcrops the Raigón Formation, usually considered a Pliocene unit. However, according to some mammals recorded and optically stimulated luminescence ages obtained from terminal facies, a Lower to Medium Pleistocene age should not be discharged for part of the unit. The Pleistocene mammals suggest open and semiopen environments based on dental adaptations and isotopic studies. 2.11.0.0 2.11.0.0 2.11.0.0

We report on remains of the buccal apparatus and possible associated structures for the Late Cretaceous ammonite Maorites seymourianus from the López de Bertodano Formation (Antarctic Peninsula). This is the first description of these structures for the family Kossmaticeratidae. Further, we discuss the most likely taphonomic processes taking place that allowed this exceptional preservation. Reflectance Transformation Imaging (RTI) technique was employed in this work to better document the faint structures. We briefly provide a review of this method and its potential importance for paleontological studies because it seems that this powerful technique has been largely overlooked by paleontologists.

This paper presents a historical outlook of the scientific and academic track of, at least, two disciplines that used to work together on the palaeoenvironment and its transformation since humans’ appearance. This inter and multidisciplinary practice became consolidated as the zooarchaeological research line that currently has great development not only in Argentina but also in the world. In this long academic history, Ameghino’s ideas have been proven steadily to the present. Our goal is to display the main concepts from the interdisciplinary production of biologists and archaeologists working in the Pampean and Patagonian regions.

In this research, we reconstruct the paleoenvironmental conditions from a sedimentary record of a wetland (mallín) located in the Patagonian steppe near to the Subantarctic forest on the northeastern shore of the San Martín Lake basin (SW Santa Cruz, Patagonia, Argentina). The Mallín Ñire (49° 00’ 23.5” S; 72° 13’ 34.5” W) presents a basal age of 10,200 cal. years BP and its pollen content, carbon isotopes, and stratigraphy were analyzed. The relationship with modern pollen assemblages from surface sediment samples allows us to interpret changes in the fossil record. Between 10,200 and 9,000 cal. years BP, we can infer a grass-shrub steppe with dwarf-shrubs under arid conditions and between 9,000 and 6,500 cal. years BP, a grass steppe dominated under an increase of moisture availability. Conditions became drier until 4,000 cal. years BP; later, a grass-shrub steppe developed, which suggests an environmental transition like the modern ones. The last 1,400 cal. years BP present high paleoenvironmental variability. The integration with other sequences allowed us to interpret the regional changes during the Holocene related to moisture availability by precipitation changes related to the westerly variations.