Ontogeny and associated changes of the extinct sloth Simomylodon uccasamamensis (Xenarthra, Mylodontidae) from the Pliocene of the eastern Puna, Argentina.

Within Xenarthra (Eocene-Recent), Folivora developed (late Eocene-Recent) a remarkable diversity with respect to ecology and taxonomy over its evolutionary history. Knowledge of the diversity achieved by members of this clade in high-altitude areas of South America (i.e., Altiplano and Puna regions of Peru, Bolivia, and northwestern Argentina) has been improved in recent decades. A particular example involves the late Neogene Mylodontidae Simomylodon uccasamamensis, known mostly from multiple specimens recovered from the Bolivian Altiplano. Although several anatomical descriptions of this ground sloth have been published, almost nothing is known about its ontogenetic development and the associated morphological changes. Here we describe and compare new specimens of S. uccasamamensis from the upper level of the Tafna Formation (Pliocene) in the eastern Puna (ca. 3800 masl), Argentina, representing the southernmost record of this species. The new material is represented by specimens showing different ontogenetic stages, from infant to adult. One subadult specimen reached an estimated body mass of ca. 232 kg. The comparative study of external and internal morphology (the latter obtained from CT scans and radiography) shows remarkable changes in the mandible and molariforms associated with ontogeny; in addition, evidence suggests that the mfs2-3 are the first functional teeth, followed by mf1 and cf1. Based on our body mass estimates (ca. 232 kg.), we inferred an average lifespan of 14 years, 9-month gestation time, and sexual maturation at 4.1 years, quite similar to the values we obtained based on estimated body masses of adult specimens from Bolivia published by previous authors. Along its latitudinal distribution (ca. 14° S-21° S) S. uccasamamensis co-occurred with other ground sloths (e.g., Megatheriinae, Thalassocninae, and Scelidotheriinae), suggesting niche partitioning. The presence of this medium-sized ground sloth is consistent with the similarity between the faunas of eastern Puna and the Bolivian Altiplano during the Pliocene, which is also concordant with what was observed in other clades, such as Rodentia and Notoungulata.

A review of the Quaternary Scelidotheriinae (Mammalia, Xenarthra, Tardigrada) from the Tarija-Padcaya basin, Bolivia.

The Mylodontidae Scelidotheriinae (Mammalia, Xenarthra, Tardigrada) are a diversified clade of South American fossil ground sloths, with a wide geographic distribution, especially in high and middle latitudes. According to the last revision, the Quaternary diversity includes the genera Scelidotherium, Catonyx, and Valgipes. The clade Scelidotheriinae is well represented in the Pleistocene of the Tarija-Padcaya basin, and the first mention of these ground sloths correspond to the middle of the XIX Century. Since then, several species (i.e., Scelidotherium tarijensis, Scelidodon tarijensis, Scelidotherium capellini) have been reported as inhabiting the Tarija-Padcaya basin during the Pleistocene. Despite the abundance of fossil records of Scelidotheriinae in this area, no modern taxonomic revisions are available. In consequence, in this contribution a revision of the remains assigned to Scelidotheriinae from the Tarija-Padcaya basin is accomplished, and some biostratigraphic and geographic implications are discussed. Our results show that one single species (Catonyx tarijensis) can be recognized in the studied area, whereas a supposed smaller one (Scelidotherium patrium) actually corresponds to juvenile specimens of C. tarijensis.

Regarding the real diversity of Glyptodontidae (Mammalia, Xenarthra) in the late Pliocene (Chapadmalalan Age/Stage) of Argentina.

A large diversity of Glyptodontidae has been proposed as characterizing the Chapadmalalan Age (Pliocene). Most of these taxa were recognized on the basis of partial dorsal carapaces and/or caudal tubes, whereas the main diagnostic characteristic is a particular morphology of the exposed surface of the osteoderms. From a biostratigraphic point of view some species are biostratigraphically important. The Upper Chapadmalalan is based on the Paraglyptodon chapadmalensis biozone. Both the re-evaluation of the type and referred materials and new significant findings from the Chapadmalal and El Polvorín Formations indicate that the diversity of Pliocene Glyptodontidae is more limited than previously supposed. The particular morphology of the exposed surface of the osteoderms that characterizes some of the species actually corresponds to a taphonomic alteration, which results in a non-real ornamentation pattern. Thus, the Glyptodontinae P. chapadmalensis must be replaced as a fossil guide because neither this species nor the species included in the genera Urotherium, Trachycalyptus and Lomaphorus are well characterized. Taking into account the diversity of Glyptodontidae for this lapse, the Glyptodontinae are very scarce (a situation that contrasts with its records in the Pleistocene), whereas Eosclerocalyptus, "Plohophorini" (Plohophorus) and Doedicurinae (cf. Eleutherocercus antiquus) are among the most recorded taxa.

PRIMER REGISTRO DE TERMITEROS FÓSILES PARA EL PLEISTOCENO TARDÍO DE LA REGIÓN MESOPOTÁMICA (ARGENTINA): IMPLICANCIAS PALEOAMBIENTALES / First Fossil Termite Nests from the Late Pleistocene of the Mesopotamian Region (Argentina): Paleoenvironmental Implications

En esta contribución se da a conocer el primer registro de termiteros fósiles para la región Mesopotámica de Argentina, y su disposición espacial, al tiempo que se discuten sus afinidades taxonómicas e implicancias paleoambientales. Las estructuras fósiles pertenecen a nidificaciones de insectos sociales atribuibles a miembros de la Familia Termitidae, y se ubican en la zona de contacto entre la base de la Fm. Toropí/Yupoí (Pleistoceno tardío) y el tope de la Fm. Ituzaingó (Mioceno tardío-Plioceno). Se las identifica en los alrededores del Arroyo Toropí (28°36' S y 59°02' W), Departamento Bella Vista, provincia de Corrientes. El estudio de las nidificaciones y su disposición espacial se realizó en cinco campos de termiteros mediante su relevamiento y descripción morfológica. La morfología de las estructuras estudiadas coincide claramente con la de los nidos de termitas, en donde resulta característica una fuerte muralla externa. La caracterización de campo, yacencia, desarrollo, frecuencia, tamaños e interrelaciones de los termiteros fósiles y actuales sugieren una estrecha similitud con montículos del género Cornitermes. La morfología presente muestra también cierta semejanza con Tacuruichnus farinai, descripta para el Piso/Edad Marplatense (Plioceno) de la región Pampeana. Por otro lado, el análisis fitolítico indicó que las cantidades y las morfologías fitolíticas son semejantes tanto en los termiteros actuales como en los fósiles. Desde un punto de vista paleoambiental, la abundancia de estos termiteros en el contacto entre las mencionadas unidades indicaría la existencia de suelos bien desarrollados, con abundante vegetación graminosa y condiciones húmedas y cálidas con estacionalidad marcada.

In this contribution we show the first termite nests fossil record presence from the Mesopotamian region of Argentina and its spatial distribution. At the same time taxonomic affinities and paleoenvironmental implications are discussed. The discovery takes place in the contact area between the base of the Toropí / Yupoí formations (late Pleistocene) and the top of the Ituzaingó Fm. (late Miocene-Pliocene), around the Toropí stream (28°36' S y 59°02' W), Bella Vista Department, Corrientes province. These fossil structures belong to nestings of social insects, such as the termite nests type. They could be attributable to representatives of the Termitidae Family. The study of nestings and their spatial arrangement was carried out on five termite nest fields, by surveying and detailed morphological description thereof. The morphology of the studied structures clearly matches with termite nests, with a typical strong outer wall. Characterization of field development, frequency, size and relationships of extant and fossil termite nests suggest a close similarity with mounds of the Cornitermes genus. Furthermore the morphology of these fossil termite nests also shows some resemblance to Tacuruichnus farinai, described for the Marplatanse Stage (Pliocene) of the Pampean region. From a paleoenvironmental point of view, the abundance of these termite nests in the contact between these units indicates the existence of well developed soils with abundant grassy vegetation and humid warm conditions with marked seasonality.

A new species of Neosclerocalyptus Paula Couto (Mammalia: Xenarthra: Cingulata): the oldest record of the genus and morphological and phylogenetic aspects.

Among South American Quaternary Glyptodontidae (Mammalia, Cingulata), Neosclerocalyptus Paula Couto represents one of the best known genera. Prior to this contribution, four species were recognized. N. pseudornatus (Ameghino) and N. ornatus (Owen) (Ensenadan Age/Stage, early-middle Pleistocene); N. gouldi Zurita (Bonaerian Age/Stage, middle Pleistocene-late Pleistocene), and N. paskoensis (Zurita) (Lujanian Age/Stage, late Pleistocene-early Holocene). One of the most notable characters of the species of the genus is a modified area located in the distal part of the nasals, recently interpreted as a neomorphic structure derived from the ossification of the nasal cartilages. In this contribution, a new species of Neosclerocalyptus (N. castellanosi sp. nov.), which in turn represents the oldest record of the genus, is presented and described. In addition, a cladistic analysis is carried out to test the monophyly of Neosclerocalyptus and the phylogenetic position of this new species. The material comes from Vorohuean (late Pliocene) levels in the surroundings of Mar del Plata, Buenos Aires Province, Argentina. Among other morphological characters, this new species has ossified nasal cartilages restricted to the latero-dorsal area of the nasals, whereas in the remaining species these structures are more expanded and both sides contact in the midline of the skull. In turn, the phylogenetic analysis confirmed the monophyly of Neosclerocalyptus, whereas N. castellanosi sp. nov. appears closely related to N. pseudornatus, being N. ornatus the sister taxa of this clade. On the other hand, N. gouldi + N. paskoensis constitute the other clade. The clade constituted by Hoplophorus euphractus Lund + Panochthus intermedius Lydekker constitutes the sister taxa of Neosclerocalyptus.