Sergio O. Lucero

Registros de cetáceos del Mioceno Tardío de Entre Ríos, Argentina

Records of cetaceans from the Late Miocene from Entre Rios, Argentina. In this paper cetacean remains from the Parana Formation (Late Miocene) of the Entre R...

Stranded humpback whale (Megaptera novaeangliae) (Cetacea: Balaenopteridae) in Paraná River Delta, Buenos Aires Province, Argentina. Comments on the occurrence of marine mammals in the La Plata River Basin

The humpback whale ( Megaptera novaeangliae ) is distributed among most oceans and seas of the globe (except Mediterranean Sea). These whales migrate from feeding regions in the Antarctic waters to breeding areas in tropical and subtropical seas. Here we report the stranding of a female young humpback whale, which was founded dead in the vicinity of the Talavera Island, in the Parana River Delta, Buenos Aires Province, Argentina. From the analysis of mitochondrial cytochrome c oxidase subunit I gene sequences, two novel haplotypes were found, totalizing four haplotypes described for the species. In the La Plata River Basin this species was found only twice at the end of the XIX century. Thus, the new finding constitutes an important addition to the list of cetaceans that occurs in Uruguay, Parana and La Plata Rivers.

Análisis osteológico de ejemplares delfín de Fraser (Lagenodelphis hosei Fraser, 1956) provenientes de la costa de la provincia de Buenos Aires, Argentina

The presence of Lagenodelphis hosei in temperate waters of the Argentinian Sea is a rare event because of its preference for pelagic and tropical waters. Wit...

Historical record of Holochilus vulpinus (Rodentia, Sigmodontinae) from northern Patagonia, Argentina

Abstract Marsh rats of the species Holochilus vulpinus inhabit mesic and humid environments. For this reason, it is frequently used in paleoenviromental studies to infer past humid conditions. Holocene archeological record indicates that H. vulpinus had a wider geographical distribution than today. Its regional extinction in north Patagonia at the XIX century was attributed to the dry and cold Little Ice Age (LIA). Here we present the finding of a specimen of H. vulpinus from northeastern Patagonia (Valcheta stream, Río Negro province, Argentina), just at the end of LIA. Implications of this novel historical record are discussed.

Notes on the taxonomy of mountain viscachas of the genus Lagidium Meyen 1833 (Rodentia: Chinchillidae)

Mountain viscachas of the genus Lagidium Meyen 1833 are medium-to-large hystricomorph rodents (1.5 -- 3 kg) that live in rocky outcrops from Ecuador to southern Argentina and Chile. Lagidium includes more than 20 nominal forms, most of them based on one or two individuals, which were first described during the 18th and 20th. Subsequent revisions reduced the number of species to three to four, depending upon the author. Within the genus, Lagidium viscacia (Molina, 1782) is the most widely distributed species, with populations apparently extended from western Bolivia to southern Argentina and Chile. We reviewed > 100 individuals of Lagidium, including skins and skulls, most of them collected in Argentina. We performed multivariate statistical analysis (i. e., principal component analysis [PCA], discriminant analysis [DA]) on a subset of 55 adult individuals grouped according to their geographical origin, using 16 skull and tooth measurements. In addition, we searched for differences in cranial anatomy across populations. PCA and DA indicate a moderate overlap between individuals from southern Argentina, on one hand, and northwestern Argentina, western Bolivia and northern Chile, on the other. The external coloration, although variable, showed a predominance of gray shades in southern Argentina and yellowish gray in northwestern Argentina. Specimens of southern Argentina were characterized by their bigger overall size, nasals expanded in its front half, and narrow dorsal root of the zygomatic process of the maxillary, while those of northwestern Argentina were smaller, with nasals lacking expansions and the dorsal root of the zygomatic process of the maxillary broad. Our study provides coincident results from quantitative and qualitative morphology that allow us to clearly differentiate southern Argentinean populations of Lagidium viscacia from those of northwestern Argentina and western Bolivia. The oldest available name for the populations from southern Argentina, sometimes referred as L. boxi, is moreni, a taxon with an unclear type locality. The status of the populations from northwestern Argentina and western Bolivia is relatively more complex, since at least eight nominal forms were described from this general area and because our sampling is far from being extensive. In addition, is also unclear if these populations correspond to one or more species, as well as their degree of differentiation from L. viscacia s. s. Without analyzing topotypes of all nominal forms and adequate samples across the entire distribution range, it is premature to put forward a formal taxonomic proposal; as such, at this moment we prefer to maintain those populations from northwestern Argentina, western Bolivia and central Chile under L. viscacia.

Presencia del género Ctenomys (Rodentia, Ctenomyidae) en el noreste de la provincia de Buenos Aires, Argentina

Presence of the genus Ctenomys (Rodentia, Ctenomyidae) in northeastern Buenos Aires province, Argentina. The genus Ctenomys found at the locality of Lima, in the northeastern region of Buenos Aires province, is reported in this paper. The finding of specimens of this genus is located more than 150 kilometers to the North of previous mentions for the province, being possible its adcription to C. talarum or to any other species from the mesopotamian region of Argentina. Previous papers indicate the presence of fossil Ctenomys in several localities in northern Buenos Aires province, and suggest that the genus disappeared from this region before the XIXth century. Thus, the record of living Ctenomys in northeastern Buenos Aires province provide new interesting clues about the biogeography of this genus in the area.