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The vertebrate fossil record of the Pampean Region of Argentina occupies an important place in South American vertebrate paleontology. An abundance of localities has long been the main basis for constructing the chronostratigraphical/geochronological scale for the late Neogene–Quaternary of South America, as well as for understanding major patterns of vertebrate evolution, including the Great American Biotic Interchange. However, few independently-derived dates are available for constraining this record. In this contribution, we present new 40Ar/39Ar dates on escorias (likely the product of meteoric impacts) from the Argentinean Atlantic coast and statistically-based biochronological analyses that help to calibrate Late Miocene–Pliocene Pampean faunal successions. For the type areas of the Montehermosan and Chapadmalalan Ages/Stages, our results delimit their age ranges to 4.7–3.7 Ma and ca. 3.74–3.04 Ma, respectively. Additionally, from Buenos Aires Province, dates of 5.17 Ma and 4.33 Ma were recovered for "Huayquerian" and Montehermosan faunas. This information helps to better calibrate important first appearances of allochthonous taxa in South America, including one of the oldest records for procyonids (7.24–5.95 Ma), cricetids (6.95–5.46 Ma), and tayassuids (> 3.74 Ma, oldest high-confidence record). These results also constrain to ca. 3 Ma the last appearances of the autochthonous sparassodonts, as well as terror birds of large/middle body size in South America. South American faunal turnover during the late Neogene, including Late Pliocene extinctions, is interpreted as a consequence of knock-on effects from global climatic changes and initiation of the icehouse climate regime. [ABSTRACT FROM AUTHOR]

Late Oligocene caviomorphs represent one of the most important early adaptive radiations of this group of rodents. They show a high taxonomic diversity and a wide geographic distribution, with those found in the upper Oligocene of Salla (Bolivia) and Patagonia (Argentina) being particularly diverse. However, caviomorphs from the Deseadan South American Land Mammal Age in other latitudes are still scarcely known. In this contribution, we describe new caviomorph rodents from the Deseadan levels of Quebrada Fiera locality (Mendoza Province; central-western Argentina) and evaluate their systematic and paleobiogeographic significance. The taxonomic composition of the caviomorphs from Quebrada Fiera reveals a complex biogeographic history, as we recognize one endemic Cavioidea (Asteromys puelche sp. nov.) and two Chinchilloidea: one with Patagonian affinities (Cephalomys sp.) and another with a wide distribution in South America (Incamys bolivianus). Asteromys puelche sp. nov., shows closer phylogenetic affinities with the Bolivian A. bolivianus than with the Patagonian A. punctus. These rodents, in common with the whole mammalian association from Quebrada Fiera, show a mix of endemic taxa and others shared with higher and lower latitudes. [ABSTRACT FROM AUTHOR]

Noninvasive computed tomography (CT) scanning techniques performed on the high-quality preserved holotypes of Mendozahippus fierensis (grouped within the paraphyletic 'Notohippidae') and Gualta cuyana (Leontiniidae) allowed a thorough description of both endocasts, not only associated with the brain but also with closely related endocranial spaces, which proved to be highly diagnostic among Notoungulata and relevant from a paleobiological perspective. The specimens come from Quebrada Fiera (Mendoza, Argentina), an upper Oligocene locality extensively studied, especially during the last decade. Regarding brain endocast proportions and neocortical complexity, M. fierensis shows morphological affinities to coeval 'notohippids,' whereas G. cuyana resembles Leontinia gaudryi. An acute olfaction is inferred from the large olfactory bulbs and piriform lobes. Conversely, evidence concerning the development (and implications) of some necortical areas (i.e., somatosensory cortex and auditory cortex) were inconclusive. The encephalization quotients are around those previously reported for 'notohippids' and Toxodontidae Nesodontinae, and slightly lower than in Typotheria (except for Mesotheriidae). Other endocranial traits previously unexplored (such as the transverse diploic communication between the temporal sinuses in M. fierensis and the large temporal sinuses inferred for G. cuyana) show that there is relevant variability within Toxodontia that deserves further research. Extending similar approaches to early diverging taxa will certainly contribute to a better understanding of the morphological evolution of the brain, special sense organs, and associated blood circulation pattern in toxodontians and notoungulates in general. [ABSTRACT FROM AUTHOR]

Late Cenozoic sediments in the Sierras Pampeanas of La Rioja and Catamarca provinces, Northwestern Argentina, have yielded fossil mammal remains from the Salicas Fm. Herein, we provide a taxonomic review of previously published material and new fossils from El Degolladito area, plus the San Blas area, and north of the Sierra de Mazán region (Villa Mervil, Villa Mazán, Santa Teresita, and Salar de Pipanaco localities). Zircon dating of volcaniclastic levels of the Salicas Fm localities reveals that the fossil vertebrates span from ca. 8.7 to 2.4 Ma (Late Miocene–Early Pleistocene), which in El Degolladito area (ca. 8.7–7.9 Ma) is more abundant and taxonomically rich and includes Metatheria (cf. Thylatheridum sp., Lycopsis sp.), Rodentia (Cardiomys sp., Prodolichotis prisca , Caviidae sp. A., Lagostomus pretrichodactyla , Metacaremys primitiva , Pseudoplataeomys elongatus , Tetrastylus sp.), Meridiungulata (Neobrachytherium sp., Hemihegetotherium torresi , Paedotherium minor , Protypotherium minutum , Typotheriopsis sp.), and Xenarthra (Eosclerocalyptus proximus , Stromaphorus compressidens , Nopachthus coagmentatus , Chasicotatus peiranoi , Paleuphractus argentinus , Proeuphractus limpidus , Prozaedyus sp., Vetelia gandhii , Pampatheriidae indet, Pilosa indet.). Lagostomus cf. L. pretrichodactyla , H. torresi , and Vetelia sp. have also been recovered in the outcrops near San Blas (without dating), whereas to the north of the Sierra de Mazán (ca. 5.7–2.4 Ma) only remains Dasypodidae, Glyptodontoinei, and N. coagmentatus have been found. Based on our analysis, it seems that the sampling conducted in El Degolladito area may have not yet fully uncovered the complete range of mammal diversity. The association from El Degolladito share affinity with those of the Late Neogene of Argentina previously referred to "Chasicoan" and "Huayquerian", like Palo Pintado Fm, "Chasicoan" faunas of Cerro Azul Fm (e.g., Cerro La Bota locality), Loma de Las Tapias assemblages A and B, which is congruent with the absolute dating obtained. • First zircon dating suggests Salicas Formation's deposition during Late Miocene to Early Pleistocene (ca. 8.7–2.4 Ma). • Mammalian assemblage at El Degolladito site (Late Miocene, Tortonian) shows affinity with Chasicoan and Huayquerian faunas. • New data expands Salicas Formation's mammal diversity in 27 taxa. [ABSTRACT FROM AUTHOR]

Hegetotheriidae are one of the most derived families of the Order Notoungulata. It is composed of two subfamilies: Hegetotheriinae, which resolves as paraphyletic in most recent phylogenies, and Pachyrukhinae, which historically is considered monophyletic. The family is recognized from late Oligocene to Pliocene and is well diversified from its earliest records. Most papers on the family are systematic studies and, to a lesser degree, investigate its phylogenetic relationships, but paleobiogeographic approaches are rare. A phylogenetic analysis was carried out using TNT, based on a previous matrix that was augmented with additional taxa and characters. Previous results are supported, viz., the paraphyly ofHegetotheriumAmeghino andPaedotheriumBurmeister, and the monophyly of Pachyrukhinae, but new conclusions arise, such as the paraphyly ofHemihegetotheriumRovereto and the monophyly ofProhegetotheriumAmeghino and Hegetotheriinae. In this work, a paleobiogeographic analysis on hegetotheriids is carried out by means of the Bayesian method using the RASP program, with the aim of estimating the possible ancestral area and vicariance, dispersal, and extinction events. This analysis shows that Hegetotheriidae and both subfamilies originated in central Patagonia (southeast of Chubut and northeast of Santa Cruz provinces). The analysis also reveals that dispersals were the predominant events, and they are related to Cenozoic dispersals to lower latitudes as global cooling advanced and new lands emerged. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free atwww.tandfonline.com/UJVP Citation for this article: Seoane, F. D., S. Roig Juñent, and E. Cerdeño. 2017. Phylogeny and paleobiogeography of Hegetotheriidae (Mammalia, Notoungulata). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1278547. [ABSTRACT FROM AUTHOR]

A new species of toxodontid notoungulate, Xotodon maimarensis n. sp., is described from the Maimará Formation (late Miocene–early Pliocene), Jujuy Province, northwestern Argentina. This is the first record of a toxodontid from the Eastern Cordillera. The specimen is housed at the Museo de Geología, Mineralogía y Paleontología, Instituto de Geología y Minería de la Universidad Nacional de Jujuy. It consists of an incomplete mandible preserving the right mandibular ramus with part of the dental series, partially preserved symphysis with all the incisors, and a small portion of the left ramus without teeth. The following characters distinguish it as a new taxon: symphysis long and narrow with slight divergence of its lateral borders; strong procumbence of lower incisors and deeply implanted i3; chin angle lower than in X. major and X. cristatus and bulging labial keel limiting strong lateral concavities. Comparative analysis in the context of the recently revised Neogene Toxodontidae indicates that the Maimará specimen shares mandibular features and dental characters with Xotodon and Mixotoxodon, differing from the latter by the more upraised symphysis. The phylogenetic position of Xotodon maimarensis n. sp. supports the taxonomic interpretation of the studied specimen as a new species of Xotodon. This new Toxodontidae increases the knowledge of the diversity and radiation of this group of notoungulates in northwest Argentina. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the taphonomic analysis of the late Miocene bone assemblage from the Cerro Azul Formation at Telén (La Pampa Province, Argentina). The faunal assemblage was assigned to the Huayquerian mammal age (late Miocene). The fossiliferous section shows a homogeneous lithology, and is interpreted as a loess deposit with two similar and slightly developed palaeosols, classified as calcic vertisols. The studied sample comprises 5598 remains anatomically and taxonomically determined. They were collected from an area of about 48,000m2, appearing randomly distributed through the section and with low density. Most remains are small- to very small-sized, disarticulated, and very fragmented. Different taphonomical histories are inferred for microvertebrates and macromammals. The microvertebrate assemblage is interpreted as the result of predator activities. After a brief period of pre-burial exposure, remains were dispersed from the original depositional area. On the other hand, a natural and gradual death process is envisaged for macromammals, followed by a long period of exposure to weathering and dispersal by physical agents. Remains of both groups, once buried, suffered the diagenetic processes of the host rock. Consequently, the fossil assemblage from Telén would represent a condensed assemblage corresponding to two distinct time spans, i.e., the accumulation of microvertebrates took place in a short time interval whereas that of macromammals occurred over a longer period, coincident with the development of both soils. [Copyright &y& Elsevier]

The apparently regular and favourable climate that characterizes the Holocene as an interglacial period shows, however, important climatic instability well documented in the Northern Hemisphere. These fluctuations from colder to warmer or wetter to drier affected both biodiversity and human societies in the last 12,000 years, although the impact in Southern America is still poorly known. We are here investigating the biodiversity of small mammal faunas, more sensitive to climatic changes than large mammals, combining taphonomic and palaeoecological data in the Argentine Pampas to better understand the global nature and effect of these Holocene climatic fluctuations. This paper is pioneering applying in this region palaeoecological methodologies practised in European sites, such as the chorotype classification and biomes overlap analyses. The Pampean Region is an ecotone with a confluence of three climatic regions where any change in climatic conditions should be easily detected. Our results, based on the palaeoecological requirements of small mammals, do not indicate severe changes, and most of the sites show climatic stability except for one of them, in which a possible trend towards present conditions (temperate/humid) can be inferred. • New palaeoecological methodologies are applied to the Pampean Region. • Microfauna is the best climatic indicator if multiproxy interpretations are considered. • Cave vs. open-air sites influence the composition of fossil small mammal assemblages. • Human activities in the past can distort palaeoecological interpretations. • Noticeable climatic events in the Northern hemisphere are soften/absent in the South. [ABSTRACT FROM AUTHOR]

The subfamily Scelidotheriinae (Xenarthra, Folivora) is a clade of extinct sloths recorded from the middle Miocene to the Pleistocene/Holocene transition in South America, namely Argentina, Bolivia, Brazil, Colombia, Chile, Peru, Ecuador, Uruguay, and Paraguay. Quaternary taxa are the best known, but the knowledge of the late Neogene representatives has been greatly improved in recent years, particularly in Argentina. New materials of Scelidotheriinae recovered from the Cerro Azul Formation (late Miocene; Huayquerian) in La Pampa and Buenos Aires provinces are here described and identified as Proscelidodon gracillimus Rovereto, and ontogenetic variations are established for the first time in this group of sloths. The comparative study has led to the taxonomical revision of other species such as P. almagroi Rovereto (from Catamarca Province) and Elassotherium altirostre Cabrera (from western Buenos Aires Province), whose type specimens are reinterpreted as subadult and juvenile individuals, respectively, of P. gracillimus ; thus, the former two become synonymous names of the latter. As the type material from Mendoza, the remains of P. gracillimus from Buenos Aires and La Pampa provinces have been recovered from Huayquerian levels, being absent from the older Chasicoan levels, within the late Miocene. In turn, the materials from Catamarca (type of P. almagroi) have less chronological precision, and could range from late Miocene to early Pliocene. • Scelidotheriinae remains from central Argentina are analyzed. • New specimens included in Procelidodon gracillimus are figured and described. • Ontogenetic variability of Proscelidodon gracillimus is described. • The geographic distribution of Proscelidodon gracillimus is expanded. • P. gracillimus is known in Mendoza, La Pampa, Buenos Aires, and Catamarca provinces. [ABSTRACT FROM AUTHOR]

Premise: Two Bignoniaceae stems with the distinctive anatomy of a liana are described from the Miocene of South America. They are the first fossil evidence of climbing habit in Bignoniaceae., Methods: The fossil lianas are siliceous permineralizations. Transverse, tangential, and radial thin sections of the woods were prepared for study using standard petrographic techniques and observed under both light and scanning electron microscopy., Results: The stems consist of wood and presumably bark (peripheral tissues). They exhibit phloem wedges, a cambial variant associated with the climbing habit in Bignoniaceae. The wood is diffuse-porous; solitary and in radial multiples vessels; alternated intervessel pitting; ray-vessel pitting with distinct borders; simple perforation plates; rays 1-3 seriate, composed of procumbent cells or body ray cells procumbent with one or two-row of upright or square marginal cells; fibers septate and non-septate, with simple to minutely bordered pits; axial parenchyma scanty paratracheal, vasicentric, septate; perforated ray cells; prismatic crystals in rays, and rays and fibers irregularly storied. The fossil stems are related to extant Dolichandra unguis-cati (L.) Miers., Conclusions: The fossils represent a new taxon, Dolichandra pacei sp. nov., which confirms the presence of a neotropical Bignoniaceae liana from the Miocene and provides the first and oldest evidence of the climbing habit in the family. Paleobotanical studies in the Mariño Formation, with the record of Bignoniaceae and Verbenaceae, and phylogenetic and biogeographical studies have great importance to understand plant evolution and diversification in South American Andes., (© 2021 Botanical Society of America.)