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A toxodontid (Notoungulata) specimen (CHN-UNLC-P-V-4) is the first fossil from the Paso de las Carretas Formation that crops out in the Río Quinto Basin (Neogene), to the east of San Luis city (Argentina). The geological study provides a new stratigraphic section and the position of sediments in the valley depocentre permits inferring an older age than that of the Río Quinto Formation, which implies an early Late Miocene age for the Paso de las Carretas Formation. This age agrees with the identified cf. Ocnerotherium intermedium (taxonomic determination supported by a phylogenetic analysis), as this species was recognised in the Chasicoan Stage/Age of San Luis Province. CHN-UNLC-P-V-4 includes a mandibular fragment with ventral extension, preserving m1–3, a symphysis fragment with incisors, and the partial upper tooth series. A body mass of ~ 1700 kg is estimated. The mandible is similar to that of Dinotoxodon and Gyrinodon, but teeth (mainly upper ones) approach CHN-UNLC-P-V-4 to O. intermedium. As the mandibular extension of this species was not established, but likely present and lower teeth have some differences, we maintain an open nomenclature for CHN-UNLC-P-V-4. The similar incisors to the holotype of ‘Neoadinotherium triangulatum’ supports the latter might belong to O. intermedium, as previously suggested. [ABSTRACT FROM AUTHOR]

Micro- and macromammal remains from Cerro La Bota (late Miocene; La Pampa Province, Argentina) are taphonomically analysed. All remains form a single sample recovered from Chasicoan sediments (facies FA2) of the Cerro Azul Formation, constituted by a lateral and vertical erosive superposition of sandstone and conglomeratic bodies, formed by episodic development of perennial streams without flow division on a loessic substrate. The analysis reveals that micro- and macromammal remains originally accumulated independently and differently. Once each type of accumulation was buried in a loessic context, the development of streams gave place to a reworking process of fossils that were finally incorporated together into the stream channel. Taphonomic characteristics of micromammals are interpreted as the result of the leftover prey accumulated by predators, probably at a den site. Instead, the macromammals respond to an attritional accumulation of individuals inhabiting the area. Even considering the reworking as an important process that affected this assemblage, the taxonomic and taphonomic evidences suggest a relatively short time for its formation. The different taphonomic histories of the remains evidence a complex association that differs from other assemblages from the Cerro Azul Formation previously analysed, and it is here assigned to the channel-lag taphonomic mode. [ABSTRACT FROM AUTHOR]

We describe new remains of notoungulates from the Cerro Azul Formation (late Miocene) in La Pampa Province and reassign others previously studied, helping to precise the taxonomic diversity of 25 fossiliferous localities of this formation. Geomorphological context previously described for the area provides data to place some localities in a temporal sequence. The following Notoungulata are recognised: Protypotherium minutum (Interatheriidae), Paedotherium minor, Tremacyllus impressus, Hemihegetotherium achataleptum, H. torresi, and Hemihegetotherium sp. (Hegetotheriidae), Typotheriopsis silveyrai, T. chasicoensis, and Pseudotypotherium subinsigne (Mesotheriidae), and Pisanodon nazari, Hemixotodon chasicoensis, and cf. Stenotephanos plicidens (Toxodontidae). This study allows adding new localities to the biochronological sequence previously proposed based on the evolutionary pattern of the octodontoid rodents. Chasicoan and early Huayquerian (as herein considered) faunal assemblages present higher diversity of notoungulates than those assigned to late Huayquerian. Some localities lack a representation of taxa significant enough to precise their biochronological position within the late Miocene. The difference in the notoungulates representation along the Chasicoan–Huayquerian ages may be due to climatic changes that affected the centre of Argentina from late Miocene to early Pliocene. [ABSTRACT FROM AUTHOR]

This contribution discusses the interatheriids from Quebrada Fiera, a Late Oligocene locality in the south of Mendoza Province. In addition, the taxonomic status of the Deseadan interatheresPlagiarthrus clivus,Argyrohyrax proavus,Argyrohyrax proavunculus, ?Argyrohyrax acuticostatus,Progaleopithecus fissurelatus,Progaleopithecus tournoueri, andNotohyrax conicusis discussed. We recognise in Quebrada FieraA. proavusandProgaleopithecussp. A possible third taxon is represented by one specimen that shows a combination of features that do not permit accurate assignment. These new remains, in combination with a systematic study of Deseadan interatheres, allow for a better definition of each recognised taxon, extended diagnoses, and clarification of some long-standing taxonomic misconceptions. Indeed, the priority ofA. proavusoverP. clivusis established, and the latter is proposed as anomen dubium. Associated deciduous and permanent dentition and some limb bones provide new data on the ontogenetic variation and postcranial morphology ofArgyrohyrax. Phylogenetic analysis supports the taxonomic determinations and placesA. proavusin a basal position with respect toArchaeophylusorProgaleopithecus. Documented fossil records ofArgyrohyraxandProgaleopithecusin Mendoza extend the known range to middle latitudes in central west Argentina; these taxa expand the list of mammals from Quebrada Fiera with Patagonian affinities. [ABSTRACT FROM PUBLISHER]

The study of juvenile remains ofPaedotheriumBurmeister from Cerro Azul Formation (La Pampa Province, Argentina; late Miocene) is presented. Upper and lower deciduous dentition (or permanent molars supposed to be associated with non-preserved deciduous teeth) are recognised. Several ontogenetic stages are distinguished among juveniles, according to the degree of wear and the replaced deciduous teeth. Besides, some morphological and metrical differences are observed along the crown height. Deciduous cheek teeth are high-crowned and placed covering the apex of the corresponding permanent tooth. The height of the crown and the degree of wear allow establishing the pattern of dental replacement of deciduous and permanent premolars in a posterior–anterior direction (DP/dp4–2 and P/p4–2), as well as the eruption of M/m3 before DP/dp4 is replaced. Some of the studied remains are recognised as young individuals ofTremacyllusAmeghino, but with complete permanent dentition, which leads to propose a different timing in the dental replacement with respect toPaedotherium; they also allow the establishment of an opposite premolar eruption pattern, from P/p2 to P/p4. This knowledge of the deciduous dentition ofPaedotheriumsuggests the need of revising the morphological and metrical characters previously used for defining species within this taxon. [ABSTRACT FROM PUBLISHER]

Salinas Grandes de Hidalgo (La Pampa Province) is a relevant locality of the Cerro Azul Formation in central Argentina because of its abundant and diverse vertebrate remains, including representatives of Reptilia, Aves and mostly Mammalia. Concerning previous records, the present faunal list adds one Argyrolagidae marsupial, one Ctenomyidae and two Caviidae rodents, as well as the first detailed analysis and description of glyptodonts from the Cerro Azul Formation in La Pampa Province. New geological information is added about the two fossiliferous outcrops included in Salinas Grandes de Hidalgo area. The classically studied outcrop located in the saline lake and the nearby one in the so-called ex-Autódromo, both herein correlated based on lithostratigraphy, particularly by the presence of paleosols in the intermediate section of the sedimentary succession. These sandy silts deposits in the base of the outcrops indicate the development of poorly confined flows and intervals of surface stabilisation by paedogenesis. We offer a biochronological interpretation based on a recently published U-Pb detrital zircons dating (5.9 ± 0.4 Ma) and the presence of significant taxa such as octodontoid rodents recovered from the dated levels and below it. From a paleoenvironmental viewpoint, we infer variations from woodlands to open environments. [ABSTRACT FROM AUTHOR]