Sparassodonts were the main mammalian predators during most of the Cenozoic in South America. The lower Eocene Itaboraí Basin/ Formation includes the second oldest fossil records of this group in South America: Patene Simpson and cf. Nemolestes Ameghino. Patene is by far the most abundant sparassodont from this formation, with more than 30 specimens referable to a single taxon, Patene simpsoni Paula Couto. Some specimens recovered from the Quebrada de Los Colorados Formation (formerly Lumbrera Formation – middle Eocene) in Northwestern Argentina have been also referred to P. simpsoni. In order to test the affinities of Patene and the taxonomy of the Argentinean specimens, we performed a review of the genus. Specimens of Patene from Northwestern Argentina show significant differences from the specimen from Brazil, including: smaller size; a relatively larger paraconid; and smaller metaconid, entoconid and hypoconid. As a result, the specimens from the Quebrada de Los Colorados Formation are assigned to a new taxon, Patene coloradensis sp. nov. The results of our phylogenetic analysis recover Patene as a basal sparassodont and support previous hypotheses that exclude Patene from the “Hathliacynidae”. The results also supported the hypothesis that Allqokirus australis Marshall & Muizon and Mayulestes ferox Muizon from the Tiupampa Basin (Santa Lucía Formation, lower Paleocene – Tiupampan SALMA), Bolivia, are the oldest known representatives of the Sparassodonta. The results also supported the monophyly of the Pucadelphyda with the inclusion of the Jaskhadelphyidae and closely related taxa in this group in addition to the Pucadelphyidae and Sparassodonta. The late Cretaceous North American Varalphadon Johanson was not recovered as a representative of the Sparassodonta in our phylogenetic analysis. Based on our results and the current fossil record, the Sparassodonta should be considered an endemic South American lineage.

Astrapotherium is the best-known member of the placental order Astrapotheria. This large herbivore inhabited the Patagonian ecosystems during early and middle Miocene times. The genus is widely represented in the early Miocene Santa Cruz Formation, with a dozen nominal species, of which Astrapotherium magnum and Astrapotherium burmeisteri are the only ones herein considered as valid. The middle Miocene record was limited to few fragmentary remains from the Río Frías Formation and presumably from the Collón Cura Formation, described as Astrapotherium hesperinum, a species name here interpreted as nomen vanum. Here we describe an almost complete skull with associated mandible derived from the Collón Cura Formation in the vicinities of Comallo, in Río Negro Province (Argentina). It is by far the most complete astrapothere material from middle Miocene rocks of high latitudes, and it is referred to Astrapotherium guillei sp. nov. It differs from the remaining species essentially in lacking P3, achieved convergently with the latest diverging uruguaytheriines. The astrapotheriines diversified in high latitudes during the early Miocene, but they retained a stereotyped morphotype and became progressively less diverse, unlike their Northern counterparts (the Uruguaytheriinae). Astrapotherium guillei is the latest known Patagonian astrapothere and represents the final expression of the Astrapotheriinae's decline thus far.

Molar morphology is one of the most used proxies for paleoecological inferences in mammals. Since the XIX century, several authors associated dental morphological traits with the diet of an animal by means of qualitative and descriptive analyses. More recently, different studies of tooth function have associated various quantitative traits of tooth shape (i.e., morphometric ratios or angles) with the different items consumed by the animal. However, because different inferences of diet for the same species can be found in the literature, it is crucial to study the power of different proxies. In this work, we compared the utility of classic morphometric indices (relative lower grinding area, lower angle and angle α) and three-dimensional landmarks configuration to infer diet. Based on a previously published dataset from our working group, we calculated the classic morphometric indices and performed three classification methods: linear discriminant analysis, quadratic discriminant analysis, and weighted random forest. Our results demonstrate that when using the geometric morphometrics approach, the diet of species is better reclassified than when using morphometric indices. Furthermore, intraspecific variation appears fundamental when making paleoecological inferences. In inferring ecological characteristics of extinct animals, studying morphological variation in extant organisms is a safeguard to prevent misinterpretations when reconstructing past ecologies.

This paper presents the study of the kerogen recovered from the Casa de Piedra Formation. The analysis includes systematic palynology, palynofacies, organic geochemistry (total organic carbon—TOC—and pyrolysis Rock-Eval) and inorganic geochemistry (X-ray fluoroescence). A new spore species is introduced: Rugulatisporites claudiae sp. nov. Three palynofacies are defined throughout the unit. The uppermost horizons, P1, fluvial in origin, include low TOC contents, a kerogen Type III,mostly terrigenous-derived, and a relatively diverse miospore assemblage largely dominated by disaccate pollen grains of umkomasiaceous/peltasperm affinity; the K/Rb ratio is high, V is scarce, and Mo is absent. The middle, lacustrine section, P2, includes relatively high TOC values, a mostly amorphous rich kerogen Type II, and abundant Botryococcus sp.; the K/Rb ratio is relatively low, V is high, and Mo is present. The kerogen at the basalmost horizon, P3,is similar to the uppermost section, but includes relatively high percentages of amorphous organic matter and Botryococcus sp.; the K/Rb ratio is the lowest of the section, V is relatively low, and Mo is absent. The kerogen from the lacustrine P2 exhibits a moderate hydrocarbon genetic potential (ca. 3 to 31 kg HC/ ton).

During the late Neogene, the Mediterranean Sea was connected with the Atlantic Ocean by two straits: the northern Betic Strait and the southern Rifian Strait. In this paper, we analyze the main palaeoenviromental changes produced in the western sector of the Betic Strait during the late Tortonian–middle Messinian (7.4–6 Ma). The temporal evolution and statistical analysis of benthic foraminiferal assemblages both in cores and surface sections of the western Guadalquivir Basin (SW Spain) allow drawing an initial important deepening from the late Tortonian calcarenite coastal areas to the well oxygenated, upper slope palaeoenvironments of the latest Tortonian to early Messinian, with a latest Tortonian condensed horizon composed by glauconitic silts deposited in the middle-outer shelf. The lower Messinian silts and clays (7.2–6.3 Ma) were deposited in a upper slope scenario, with a small oxygen depletion at 6.48 Ma. The 6.3–6.2 Ma interval was characterized by an important sea level drop and the presence of low oxygenated, outer shelf palaeoenvironments in this area, coinciding with a global glaciation. Prior to the Messinian Salinity Crisis (5.97–5.33 Ma), the upper slope palaeoenvironments were initially re-established (∼6.2–6.1 Ma) and finally a new regressive period (∼6 Ma) preceded Messinian Salinity Crisis.