A comparison between the Paleogene and Neogene marine assemblages in South America suggests a major turnover among penguins by the late Miocene, with the disappearance of the stem Sphenisciformes and the rise of the modern penguins. However, isolated specimens attributed to Palaeospheniscus from the late Miocene of Chile suggest that stem and crown taxa coexisted until the end of the Miocene. To clarify the stratigraphic range of Palaeospheniscus and determine how long the stem Sphenisciformes persisted in South America, the present study offers a revision of its putative records in Chile (Bahía Inglesa and Coquimbo formations), Peru (Chilcatay Formation), and South Africa (Ysterplaats site). In order to reliably discriminate isolated humeri of Palaeospheniscus from Spheniscus, twelve potential discriminating characters were identified and evaluated. Despite the existence of a wide range of variability and overlap, these humeri can be discriminated using large sets of characters, such as a transverse ligament sulcus connected with the capital incisure by a sulcus, or the lack of the proximal ligament pit in Palaeospheniscus. The putative record of Palaeospheniscus in the late Miocene—Pliocene of Chile and early Pliocene of South Africa is discarded, restricting its stratigraphic range to the early and middle Miocene of Argentina and the middle Miocene of Peru. This reduces the biochron of the genus from 18 Ma to a maximum of 11 Ma and suggests that the middle Miocene was a crucial time for the establishment of modern seabirds communities in general and penguins in particular.

Living capybaras are a unique group of rodents. They have ever-growing cheek teeth with a complicated occlusal morphology that changes even after birth. Concerning fossil capybaras this morphological change, associated with increasing size, led to regard them as taxonomically highly diverse, including small species with simple dental morphology, and large species with complicated cheek teeth, considered as primitive and derived, respectively. Recently, it was proposed that the different morphs found in each locality actually represent individuals of different ontogenetic stages of a population or successive populations, rather than a multiplicity of coeval species in different stages of evolution. For the Pliocene, the richest locality for capybaras is Farola Monte Hermoso on the southern coast of Buenos Aires Province. This locality yielded four nominal species of capybaras, three of them are a small morph (Phugatherium cataclisticum Ameghino, “Anchimysops villalobosi” Kraglievich, “A. ultra” Kraglievich) and the other a large one (“Chapalmatherium perturbidum” (Ameghino)). In this paper we propose that they represent juveniles and adults of one species, P. cataclisticum. In order to evaluate the phylogenetic position of Phugatherium within Cavioidea a cladistic analysis was performed modifying a previously published combined matrix of morphology and DNA sequences. Phugatherium forms a monophyletic group and is the sister group of modern capybaras. Within Phugatherium the most basal species is P. novum Ameghino, whereas the type species P. cataclisticum is the sister group of P. saavedrai Hoffstetter, Villarroel and Rodrigo.

Fragmentary anuran remains in the Ameghino Collection in the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” were recently considered as belonging in Ceratophryidae (the clade of the South American horned frogs) and coming from middle—late Oligocene sediments exposed south of Lake Colhue Huapi, Chubut, Argentina. However, both the taxonomic placement and the geographic and stratigraphic origin attributed to this material are problematic. A new study of these remains show they possess several features that allow their attribution to the extant genus Ceratophrys Wied-Neuwied. The available information on the collection locality of this material is dubious —namely Gran Barranca, where rocks range from the middle Eocene to early Miocene in age. Additionally, details of the history of this collection and the specimen itself suggest that its provenance should better be considered unknown.

POLLEN RECORDS FROM HOLOCENE DEPOSITS IN SOUTHEASTERN PATAGONIA, ARGENTINA: THEIR APPLICATION ON PALEOENVIRONMENTAL RECONSTRUCTION. This work presents the pollen analysis of deposits from southeastern Patagonia (Argentina) aimed to reconstruct changes in vegetation and environmental conditions and its relationship to huntergatherer groups who inhabited the area. Pollen sequences from an archeological site (cave Cóndor 1) and an eolian-colluvial deposit with a pedogenesis process in the upper section corresponding to the late Holocene were analyzed. There is a change at the base of the sequence, from an Ephedra-dominated steppe to a grass-dominated steppe, indicating an increase in water availability. Both a lower humidity and a rise in temperature are suggested by increasing bushes during the early Holocene. The lack of pollen between 3250 and c. 1200 cal. yr BP may be related to the intensity of human activities. Pollen assemblages dated between c. 1050 and 600 cal. yr BP, suggest conditions in the area were drier than at present. Establishment a grass-dominated steppe and a soil layer at c. 600 cal. yr BP suggest more stable environmental conditions and an increased hydric availability. Increased erosion rates over the past few centuries produced an eolian deposit overlaying the soil, coeval with the European settlement.

ANGIOSPERM FLORA OF PICO QUEMADO, ÑIRIHUAU FORMATION (LATE OLIGOCENE), RÍO NEGRO PROVINCE, ARGENTINA. Pico Quemado is located East of San Carlos de Bariloche, and stratigraphically placed in the lower member of the Ñirihuau Formation (late Oligocene — middle early Miocene). Fossil leaves (compressions and / or impressions) of dicotyledonous angiosperms were studied and twenty two morphotypes are described. The families identified were Nothofagaceae, Myrtaceae, Rosaceae, Myricaceae, Malvaceae and Fabaceae and the genus Nothofagus Blume was found to be the dominant. The macroflora is compared with twenty two tertiary paleofloras from Patagonia, and similarity indices obtained by the Jaccard coefficient, yielded values less than 13 %. This low index could be explained as due to the younger age of the Pico Quemado paleoflora compared to most of the other paleofloras and/ or because it thrived at a lower paleolatitude. The paleofloristic analysis suggests a temperate to cold-temperate climate and no analogous vegetation among other known Patagonian fossil floras.

The brachiopod Coolkilella aredesi sp. nov. and Calytrixia piersoni sp. nov. are proposed on the basis of specimens from the Del Salto, Río del Peñón and Agua del Jagüel formations. Their biostratigraphic implications are discussed together with new records of Septosyringothyris (Precosyringothyris) jaguelensis Lech and Streptorhynchus inaequiornatus Leanza at the top of the latter unit. The stratigraphic record, paleontological content and age of both the Tivertonia-Streptorhynchus assemblage (Moscovian) and the younger Costatumulus amosi fauna (Sakmarian—Artinskian) were reviewed and assessed based on outcrops at Quebrada Agua del Jagüel and Quebrada Santa Elena. Faunal content confirms the most recent stratigraphic, biostratigraphic and paleoclimatic frameworks. These recognize a diachronic nature of the Agua del Jagüel and Cordón del Jagüel formations, supporting the absence of an early Permian glacial event in western Argentina.

Two bryozoan taxa occurring in the Hirnatian (Upper Ordovician) deposits in western Argentina document a first postglacial community associated with a mid-to high-latitude brachiopod assemblage, known as the typical Hirnantia fauna, in the Argentine Precordillera. Helopora fragilis Hall and an indeterminate phyloporinid occur within a thin but conspicuous shell bed that overlies diamictitic deposits from the lower member of the Don Braulio Formation. The abundance of well preserved specimens of bryozoans together with the dominance of suspension feeders suggests a mid-shelf setting (offshore transition) with an intermediate to low sedimentation rate, low turbidity, and nutrient-rich conditions. Hirnantian bryozoan assemblages identified from tropical and subtropical regions are rather rare, and this assemblage represents the first high-latitude Hirnantian record. The low diversity of bryozoans may be related to high-latitude location of Argentina during the Late Ordovician. Helopora Hall occurs mainly in Laurentia with several species occurring in the Katian and with a few Hirnatian occurrences in Gondwana. This broad distribution may imply that this genus had a broad environmental tolerance. It is one of the genera that successfully crossed the Ordovician/Silurian boundary. However, although this genus shows a post-extinction diversification and a more widespread distribution in Laurentia (with numerous species recorded in the Silurian and Devonian of Canada, Russia and China), it became extinct in Gondwana. We hypothesize that environmental conditions after the Ordovician/Silurian boundary may have prevented the settlement of bryozoans and caused the extinction of Helopora in the Argentine Precordillera.