A large therian mammal from the Late Cretaceous of South America.

Theria represent an extant clade that comprises placental and marsupial mammals. Here we report on the discovery of a new Late Cretaceous mammal from southern Patagonia, Patagomaia chainko gen. et sp. nov., represented by hindlimb and pelvic elements with unambiguous therian features. We estimate Patagomaia chainko attained a body mass of 14 kg, which is considerably greater than the 5 kg maximum body mass of coeval Laurasian therians. This new discovery demonstrates that Gondwanan therian mammals acquired large body size by the Late Cretaceous, preceding their Laurasian relatives, which remained small-bodied until the beginning of the Cenozoic. Patagomaia supports the view that the Southern Hemisphere was a cradle for the evolution of modern mammalian clades, alongside non-therian extinct groups such as meridiolestidans, gondwanatherians and monotremes.

First monotreme from the Late Cretaceous of South America.

Monotremata is a clade of egg-lying mammals, represented by the living platypus and echidnas, which is endemic to Australia, and adjacent islands. Occurrence of basal monotremes in the Early Cretaceous of Australia has led to the consensus that this clade originated on that continent, arriving later to South America. Here we report on the discovery of a Late Cretaceous monotreme from southern Argentina, demonstrating that monotremes were present in circumpolar regions by the end of the Mesozoic, and that their distinctive anatomical features were probably present in these ancient forms as well.

Nuevos registros de Holochilus chacarius (Rodentia, Cricetidae) en la cuenca del río Carcarañá (Santa Fé, Argentina) y consideraciones biogeográficas / New records of Holochilus chacarius (Rodentia, Cricetidae) in the Carcarañá river basin (Santa Fé province, Argentina) and biogeographical considerations

Resumen La recolección y análisis de egagrópilas resulta un método adecuado en el estudio de presas pequeñas, debido a que permite el estudio de áreas extensas, genera gran cantidad y variedad de individuos por lote. El orden Strigiformes cuenta con el mayor número de estudios de dieta de aves rapaces a nivel mundial, destacándose los referidos a Tyto furcata con gran cantidad de contribuciones sobre el análisis de sus regurgitados. El estudio de las regurgitaciones de esta especie ha ayudado a realizar nuevas interpretaciones sobre la distribución, taxonomía y conservación de muchas especies de roedores. Aquí, se describe la presencia de Holochilus chacarius en el sur de la provincia de Santa Fe a partir de la recolección y análisis de egagrópilas de la lechuza del campanario (Tyto furcata). Estos registros amplían la distribución de H. chacarius en la provincia y contribuyen a actualizar los mapas de distribución existentes.

Abstract The collection and analysis of pellets is an adequate method in the study of small prey, because it allows the study of large areas, generates a large number and variety of individuals per lot. The order Strigiformes has the largest number of studies on the diet of birds of prey worldwide, highlighting those referring to Tyto furcata with a large number of contributions on the analysis of its regurgitates. The study of the regurgitations of this species has helped to make new interpretations about the distribution, taxonomy, and conservation of many species of rodents. Here, the presence of Holochilus chacarius is described in the south of the province of Santa Fe from the collection and analysis of pellets of the Barn Owl (Tyto furcata). These records expand the distribution of H. chacarius in the province and contribute to updating the existing distribution maps.

New record of a Mesozoic gondwanatherian mammaliaform from Southern Patagonia.

Gondwanatheria is an enigmatic mammaliaform clade distributed in the Cretaceous and Paleogene of South America, Africa, Madagascar, India and Antarctica. The Mesozoic record in South America is restricted to the Latest Cretaceous of Río Negro and Chubut provinces, Argentina and Magallanes Region of southern Chile. The aim of the present contribution is to describe a new specimen of gondwanatherian mammaliaforms from beds belonging to the Maastrichtian Chorrillo Formation, cropping out 30 km SW of El Calafate, Santa Cruz Province, Argentina. It is represented by a single molariform referable to the species Magallanodon baikashkenke with which it shares a unique combination of characters. Analysis of the unique combination of characters exhibited by Magallanodon shed doubts on the monophyly of Ferugliotheriidae and suggest that South American taxa may be closely related to each other. The wide geographical distribution and occurrence of gondwanatherians on geological units of diverse origins suggest that they were capable of facing disparate environmental conditions.

Phylogenetic tree of Litopterna and Perissodactyla indicates a complex early history of hoofed mammals.

The Litopterna is an extinct clade of endemic South American ungulates that range from Paleocene up to late Pleistocene times. Because of their unique anatomy, litopterns are of uncertain phylogenetic affinities. However, some nineteenth century authors, considered litopterns as related to perissodactyl ungulates, a hypothesis recently sustained by molecular data. The aim of the present contribution is to include litopterns and other South American related taxa in a comprehensive phylogenetic analysis together with several extant and extinct basal perissodactyl ungulates. The analysis resulted in the nesting of litopterns and kin as successive stem-clades of crown Perissodactyla. Further, litopterns are not phylogenetically grouped with any North American basal ungulate, in agreement with some previous proposals. Presence of pan-perissodactyls in South America and India indicates that southern continents probably played an important role in the early evolution of hoofed mammals.

An enigmatic plant-eating theropod from the Late Jurassic period of Chile.

Theropod dinosaurs were the dominant predators in most Mesozoic era terrestrial ecosystems. Early theropod evolution is currently interpreted as the diversification of various carnivorous and cursorial taxa, whereas the acquisition of herbivorism, together with the secondary loss of cursorial adaptations, occurred much later among advanced coelurosaurian theropods. A new, bizarre herbivorous basal tetanuran from the Upper Jurassic of Chile challenges this conception. The new dinosaur was discovered at Aysén, a fossil locality in the Upper Jurassic Toqui Formation of southern Chile (General Carrera Lake). The site yielded abundant and exquisitely preserved three-dimensional skeletons of small archosaurs. Several articulated individuals of Chilesaurus at different ontogenetic stages have been collected, as well as less abundant basal crocodyliforms, and fragmentary remains of sauropod dinosaurs (diplodocids and titanosaurians).