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Hegetotheriidae is one of the most derived families of South American notoungulates, which are known from the late Oligocene to Pliocene. Several genera of hegetotheriids have been described; most of them have been recently re-examined, but the Miocene taxa Hegetotherium and Pachyrukhos have not been revised for more than a century. Numerous species of both genera were described mainly from the Santa Cruz Formation, Santa Cruz Province, but also from the Colhuehuapian beds in Chubut Province, and the Colloncuran beds in Neuquén and Río Negro provinces, Argentina. Recently, Hegetotherium was recorded in Bolivia and Chile. Sinclair was the first reviewer to postulate some synonymies, in the first decade of the twentieth century. The present contribution provides a re-evaluation of these genera, including the study of previously unpublished materials. We conclude that Hegetotherium mirabile and Pachyrukhos moyani are the only hegetotheres in the Santa Cruz Formation (Santacrucian SALMA) with Hegetotherium novum and Pachyrukhos politus in the Colhuehuapian SALMA. Additionally, H. convexum, H. anceps, H. minum and H. andinum are proposed as synonyms of H. mirabile; H. novum is removed from Prohegetotherium; and Hegetotherium arctum is excluded from Hegetotheriidae. This taxonomic revision led to a new phylogenetic analysis of Hegetotheriidae, based on a previous data matrix, but enlarged and corrected, as some taxonomic issues concerning other genera were revealed. The analysis supports the monophyly of Hegetotheriidae and the subfamily Pachyrukhinae, as well as the monophyly of the genera Hemihegetotherium and Paedotherium, if the proposed removal of Pd. kakai from the latter is admitted. In contrast, Hegetotheriinae and Hegetotherium appear to be paraphyletic. The position of H. novum supports its removal from the genus Prohegetotherium, in which it was recently included. [ABSTRACT FROM AUTHOR]

Several systematic revisions of the Hegetotheriidae have been published in the last twenty years, but some important taxonomic work remains limited to unpublished studies. In one such thesis, the late Oligocene genera Prosotherium and Propachyrucos were revised, so that Prosotherium garzoni and Propachyrucos smithwoodwardi were considered the only valid species for each genus. Later authors loosely accepted these informal revisions, but recent phylogenetic coding has yet to accurately reflect these revisions, with character states often at odds with the known material for these genera. This study re-examines most of the fossil material assigned to Propachyrucos and Prosotherium , including both published and unpublished fossils, and contributes to a better understanding of the systematics, taxonomic diversity and early morphological evolution of the pachyrukhines. We conclude that Prosotherium garzoni and Propachyrucos smithwoodwardi are indeed the only valid species for each genus, confirming the influential but unpublished revisions that have become widely accepted. The known material for these species is clarified to aid future phylogenetic studies. At the same time, Propachyrucos aequilatus and Pr. robustus are herein considered nomina dubia. Additionally, Miocene species originally ascribed to Propachyrucos , along with unpublished material loosely assigned to the same genus, are here synonymized with other genera. Finally, several fossils previously recognized as Prosotherium sp. are here recognized as P. garzoni. [ABSTRACT FROM AUTHOR]

A new hydrochoerine rodent, Cardiatherium calingastaense sp. nov. (Caviidae), is described based on the specimen INGEO-PV 87. It was recovered from the late Miocene Las Flores Formation, cropping out at the Puchuzum locality, San Juan Province, Argentina. The new species is based on a particular combination of characters, among which the following can be highlighted: p4 with internal fissures equally deep as in Cardiatherium paranense, secondary external fissure as in Cardiatherium patagonicum, and lacking the fifth internal fissure and supernumerary internal fissure, as in C. paranense; m3 with a conspicuous labial column in the posterior ramus of the second prism; very deep primary and secondary external fissures in upper cheek teeth, the former producing a labial strong step-shaped profile in M2; sagittal crest on the parietals; bullae small in ventral view; scars of the origin of the masseter medialis muscle with an anterior projection up to the level of the incisive foramen and the maxilla-premaxilla suture. The phylogenetic analysis supports the taxonomic proposal of creating a new species of Cardiatherium and shows C. calingastaense sp. nov. as the sister group of the other species of the genus. The lineage leading to the clade Cardiatherium + largest capybaras would have originated at least during the Chasicoan SALMA (early late Miocene). Cardiatherium calingastaense sp. nov. adds to the previous record of Cardiatherium chasicoense and Cardiatherium paranense in the late Miocene of San Juan and Mendoza provinces, respectively, thus increasing the diversity of capybaras in central-west Argentina. [ABSTRACT FROM AUTHOR]

During the last decade, the Deseadan (late Oligocene) Quebrada Fiera locality, Mendoza Province, Argentina, has provided a large amount of mammal remains. Taxonomic studies have shown the presence of faunal elements common with other Deseadan associations from Patagonia and lower latitudes (Salla, Bolivia), as well as endemic taxa of different groups of mammals (Notohippidae, Leontiniidae, Homalodotheriidae, Hegetotheriidae, and Metatheria) and even a gastropod. In this work, we present a taxonomic and phylogenetic analysis of a set of postcranial fossils of three families of the suborder Toxodontia (Notoungulata). The postcranial elements are assigned to taxa previously recognized at Quebrada Fiera, such as the leontiniid Gualta cuyana and the homalodotheriid Asmodeus petrasnerus, but also to the family Toxodontidae that is represented by Proadinotherium sp. and another larger toxodontid; a few dental remains of Proadinotherium are also included as this is the first time that toxodontids from Quebrada Fiera are described. In the case of A. petrasnerus, an almost complete calcaneum allows us to expand the diagnosis of this taxon. The bones assigned to G. cuyana enlarge the anatomical knowledge of this species. In turn, the presence of the genus Proadinotherium extends its geographic distribution in Argentina and adds to the extra-Patagonian record of P. saltoni from Salla, Bolivia. Phylogenetic results do not differ much from previous analyses using postcranial characters, and the obtained consensus trees show low node supports. The various phylogenetic analyses performed here provide a more robust framework to interpret the relationships of the studied taxa. [ABSTRACT FROM AUTHOR]

In this contribution, a detailed systematic study of all species previously placed into the genus Antepithecus, a Barrancan (middle Eocene) "notopithecine" from Patagonia, is performed. In addition, other species described by Ameghino were studied and are also included in this taxon. The comparative morphological description allows corroborating and introducing new synonyms, and recognizing one valid species, Antepithecus brachystephanus. Its diagnosis is expanded and the number of specimens referred to this species is significantly increased. Morphological ontogenetic variations in dentition are recognized and compared with other "notopithecines". A particular eruption sequence of permanent premolars is ascertained for the Patagonian taxa Notopithecus, Antepithecus, and Transpithecus. These three Casamayoran "notopithecines" have their upper and lower milk molars replaced by permanent premolars in a posterior-anterior direction, P/p4, P/p3, P/p2, contrasting with other notoungulates, including the Mustersan "notopithecine" Guilielmoscottia. This peculiar eruption sequence in Casamayoran "notopithecines" and its heterogeneity within the group could reflect a relevant phylogenetic character to clarify inter-specific relationships. [ABSTRACT FROM AUTHOR]

Abstract: A recently recovered specimen of Mesotheriinae (Mesotheriidae, Notoungulata) from the late Miocene-early Pliocene of La Rioja Province (Argentina), CRILAR Pv 433, corresponds to an individual with three upper premolars, which appears to be an “anomaly” among mesotheriines. The detailed study of this specimen, however, brings up an old controversy on the interpretation of different mesotheriine specimens with three upper or two lower premolars. After being described as different taxa, these were later considered to be juvenile representatives of other known species. The three upper or two lower teeth were interpreted as the milk molars DP2–4 and dp3–4, respectively, which would be replaced in adult life by two upper (P3–4) and one lower (p4) permanent premolars. The new material leads us to set up a different interpretation. In our opinion, all these specimens actually preserve the permanent dentition, corresponding to different ontogenetic stages of more or less young individuals. This consideration implies the necessity of a deep systematic revision of the whole subfamily, keeping in mind this new point of view and the ontogenetic variation within a species. Therefore, the presence of P2/p3 is not enough to define a different taxon at this moment. Pending this taxonomic revision, the dental morphology of CRILAR Pv 433 resembles both Typotheriopsis (e.g., upper premolars with one labial sulcus) and Pseudotypotherium (e.g., P4 with lingual groove, wide median lobe of M3) as these two late Miocene genera are currently characterized. Furthermore, P2/p3 could be expelled soon in the lifetime of individuals, and even the presence of P2/p3 could be a variable character within the same taxon; if so, this might reflect an evolutionary trend to the loss of a dental element within mesotheriines, but the revision of a large sample is necessary to support or reject these hypotheses. [Copyright &y& Elsevier]

The continental deposits of the Cuyana Basin, western Argentina, have yielded the most diverse, but so far almost unstudied, Triassic ichthyofaunas of South America. Here, we review these faunas and show that only eight of the 29 named taxa can be considered valid, including the chondrostean Neochallaia, the acrolepid Challaia, Guaymayenia, a taxon of uncertain affinities, and five species of the perleidiform family Pseudobeaconiidae. The first three taxa most probably come from Middle Triassic sediments, while the pseudobeaconiids are of Late Triassic age. Other material, although not diagnostic, probably represents other species, and thus, the diversity of actinopterygians in the Cuyana basin is certainly higher than currently recognized. For the Late Triassic fish fauna, the absence of crown-group neopterygians and a single record of a sarcopterygian is noteworthy and probably indicates some degree of endemism in this fauna, also supported by the high abundance of pseudobeaconiids, which are unknown from other areas. Furthermore, on the basis of the age indicated by the fishes and the available geological information, we discuss the age of the local fauna of the Cerro Bayo, close to the city of Mendoza, and the Agua de la Zorra Formation, Uspallata. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the new mammal remains from the Río Quinto Formation, found at the Arroyo La Petra locality (San Luis, Argentina). They consist of an incomplete skull and two mandibular fragments of a macraucheniid, both with milk dentition and M1/m1 erupting, corresponding to a very young individual. Morfometrical characteristics of the specimens allow their identification as Oxyodontherium zeballosi and provide the first cranial data for this species. The holotype of this species is considered a juvenile individual. We maintain a conservative position in maintaining O. zeballosi as a valid species though based on juvenile specimens. However, a full systematic revision of the Family Macraucheniidae is needed to verify the validity and phylogenetic relationships of the taxa included in it. The identification of O. zeballosi indicates a late Miocene age for the fossiliferous level, which implies a cronoestratigraphic extension of the Río Quinto Formation, thus far considered as Pliocene in age. In addition, the presence of Oxyodontherium in San Luis Province increases the geographical distribution of this macrauchenid, whose record previously was limited to Miocene outcrops of the Paraná River (Entre Ríos Province). Its presence in the Mio–Pliocene beds of Uruguay is very doubtful because it is based on a metapodial. [Copyright &y& Elsevier]

Abstract: This paper deals with the detailed taxonomic study of the first mammal remains from the Mariño Formation in the Divisadero Largo area, Mendoza, central west Argentina. This area was well-known by the fossils recovered from the Triassic levels and particularly by the faunal assemblage from the Cenozoic levels corresponding to the Divisadero Largo Formation. Until recently, no mammal remains had been accurately reported for the Mariño Formation, Miocene in age. The specimen consists in an almost complete upper jugal series (teeth found separated from the maxillary bone except the M3) of a small Mesotheriidae (Notoungulata), which was preliminary identified as Mesotheriinae indet. The main characteristic of these teeth is their small size, significatively lesser than that of the Miocene genera Eutypotherium, Typotheriopsis and Pseudotypotherium, being closer to Mycrotypotherium from Bolivia and the Chilean species from the Chucal Formation. The direct comparison with these latter forms has allowed a more detailed study and the recognition of the material here described as cf. Altitypotherium chucalensis, with all cautions inherent to the incompleteness of the material. [Copyright &y& Elsevier]

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]