The fossil record of the puma lineage in America is sparse, and doubts have been raised about the origin, radiation, and migration events of this lineage. In this study, we present results of comparative and quantitative analyses on a complete left calcaneum, collected by Enrique de Carles at the beginning of the twentieth century. The calcaneum is relatively small-sized, slender-shaped, with a long and lateromedially compressed tubercle, calcaneal canal covered by a bridge that connects the ectal and sustentacular facets, sustentacular facet proximo-medially projected, quadratus plantae process reduced, groove for the flexor digitorum lateralis markedly delimited, and transversely oriented cuboidal facet. Comparative analysis, coupled with principle component analysis using linear measurements, allows us to confidently assign the fossil to the puma lineage. Given the preservation of a single autopodial element and its unique combination of features, we propose assigning the remain to gen. et sp. indet. The morphology of the element suggests cursorial adaptations, intermediate between living South American species and cheetahs. Despite uncertainty regarding exact stratigraphic provenance, the fossil studied represents the first carnivoran known for the Uquía Formation, and one of the earliest records of the puma lineage in America, and of Felidae in South America. These results highlight the already established high value of the Quebrada de Humahuaca for understanding the Great American Biotic Interchange and the need for future prospective campaigns in the region.

We restudy the holotype specimen and all the alleged fossil material assigned to Cayaoa bruneti Tonni from the Early Miocene marine deposits of the Gaiman Formation, Patagonia, Argentina. Cayaoa bruneti is phylogenetically placed close to the Erismaturinae (=”Oxyurinae”) that contains the diving birds. It was considered a flightless foot-propelled diving duck and represents the earliest example of flight loss in Anatidae. We carried out a comparative and morphometric descriptive study of different species of anseriforms with special attention to divers, to evaluate which is the expected intraspecific size variation within anatids to make an assignment of materials with a greater degree of certainty. Our results allow us to state that one coracoid, five humeri, two carpometacarpi, 12 femora, eight tibiotarsi, and eight tarsometatarsi can be assigned to the species. Consequently, it was possible to make a more detailed description and amend the original diagnosis.

The species Dalmanella testudinaria (Dalman) was reported thirty years ago from the Hirnantian Don Braulio Formation of the Argentinean Precordillera, but its assignment was cast in doubt by a recent revision of the species. Through a detailed morphological analysis of a large collection of specimens, attribution of the Don Braulio Formation material to D. testudinaria is now confirmed. The overlying Rhuddanian sandstones of the La Chilca Formation yielded a dalmanellid which was previously referred to as Dalmanella aff. testudinaria. The minor differences existing between these specimens and the topotype material from Sweden is interpreted as intraspecific variation and consequently they are assigned to D. testudinaria. This implies that in the Precordillera basin this species survived the second pulse of the end-Ordovician mass extinction. In the Don Braulio Formation largest shells occur in shallow-water subtidal carbonate lenses and siltstones, near the base of the posglacial transgression, reflecting deposition in well-oxygenated, nutrient-rich waters. Shell size decreases upsection reaching a minimum in the organic-rich mudstones bearing the graptolite Metabolograptus persculptus (Elles et Wood). Overall evidence suggests that low-richness and low-density of this community could be attributed to unfavorable physical environmental conditions associated with decreased food availability, and such limiting paleoecological factors are considered to be the primary cause of dwarfing. Small specimens of D. testudinaria reappear a few meters above the “extinction level” in the lower part of the La Chilca Formation of Rhuddanian age. Before becoming extinct, D. testudinaria coexisted in the Cuyania terrane with the first representatives of the Afro-South American Realm such as Anabaia Clarke and Heterorthella Harper, Boucot, And Walmsley.

Neohelice granulata is an endemic, burrowing intertidal species of crab distributed in mudflats and saltmarshes of bays and lagoons along the coast, from southern Brazil to northern Patagonia (Argentina). It is widely known in modern population studies dealing with ecology, genetics, physiology, and burrowing. However, it is known in the fossil record only from the mid-Holocene of Buenos Aires, from deposits corresponding to the last marine transgression. The material comprises eleven almost complete specimens, six isolated carapaces and six isolated chelipeds, all preserved in micritic and sandy concretions of different shapes and sizes formed within their burrows. Diagenetic processes produced dorsoventral crushing of all of the specimens to different degrees but they are generally well preserved. No burrows were unambiguously identified, but the articulated nature of the exoskeleton suggests preservation within burrows. A winter kill might have been the cause of this assemblage, which also includes molluscs, cirripeds, and vertebrates. Herein, we describe in detail and for the first time this material from Parque Pereyra Iraola, Buenos Aires, Canal de las Escobas Formation, Destacamento Río Salado Member, which includes a discussion on the taphonomy and paleoenvironmental implications of the assemblage.