The Order Notoungulata is a large group of endemic mammals widespread throughout the Cenozoic of South America. Among them, the Family Homalodotheriidae is one of the less abundant and diverse, and geographically more restricted. Its record ranges from early Oligocene to late Miocene, but only a few genera were described, mainly known from Patagonia. This paper deals with the first homalodotheriid remains recovered from Deseadan levels outside Patagonia. The material comes from Quebrada Fiera, a late Oligocene locality in southern Mendoza Province (Argentina), and mainly consists of postcranial elements. A comparative study lead to its placement in the Patagonian genus Asmodeus Ameghino, but with some significant differences from Asmodeus osborni Ameghino. Thus a new species —Asmodeus petrasnerus sp. nov.— is proposed for the taxon from Mendoza. It is characterized by: calcaneum with a subtriangular navicular facet, ectal facet with concave medial border, and not projected anterodistal end; astragalus with distal facet more medially placed than in A. osborni, without astragalar foramen, and with astragalar groove expanded; cuboid without contact with the astragalus; Mc III with posteriorly expanded proximal facet; and Mc IV with medial facets separated to the proximal edge. The material from Mendoza provides new data on the postcranial anatomy of Asmodeus and allows completing the diagnosis of this genus. The record of A. petrasnerus sp. nov. in Quebrada Fiera increases the diversity and the geographical distribution of the genus and the family during the late Oligocene.

We describe and analyze the mineralogical, geochemical and paleohistological characteristics present in hemimandibles of Paedotherium bonaerense (Ameghino) (Mammalia, Notoungulata, Hegetotheriidae). Remains were recovered from floodplain deposits of the Monte Hermoso Formation (early Pliocene). Francolite is the main mineral component in all hemimandibles, evidencing compositional changes in the internal crystalline structure during fossil-diagenesis. The similarity in the chemical composition of the fossils and the hosting rocks suggests that the enrichment of the remains with new elements was due to direct exchange with the sediments in which they were buried. Original bone microstructure shows good preservation, only affected by permineralization and microfissures. Manganese and iron oxides are the most abundant minerals infilling microstructural features and microfissures. The dark color identified on the outer surface of some remains is related to precipitation of manganese oxides. The results obtained allow us to establish the processes affecting the remains before and after burial, and thus interpret the different taphonomic histories. This work provides new information on a issue usually not considered in studies on vertebrate communities from the South American Neogene and at the same time it establishes a framework for the analysis of assemblages with similar characteristics.

Numerous fossil gastropods have been recorded in an edaphic level of the middle section of the the Aisol Formation (Mendoza Province, Argentina). This stratigraphic section bears an association of fossil mammals suggesting an early Pliocene age (possible Montehermosan SALMA). Up to four taxa of gastropods have been identified, belonging in Succinea Draparnaud (Succineidae), Gastrocopta Wollaston (Vertiginidae), Bostryx Troschel (Bulimulidae), and a new species of Radiodiscus Pilsbry and Ferriss (Charopidae). The fossil record of terrestrial pulmonate mollusks in Argentina is scarce and mainly restricted to the Quaternary. Thus, the record of these taxa is of paramount importance because it constitutes the oldest record of Gastrocopta and Succinea in Argentina, the first record of Bostryx in Mendoza Province, and the first record of the family Charopidae (Radiodiscus sanrafaelensis nov. sp.) in Pliocene deposits of Argentina.

LOWER—MIDDLE MIOCENE OSTRACOD ASSEMBLAGES OF LOMA NEGRA (BARDENAS REALES DE NAVARRA, EBRO BASIN): PALAEOENVIRONMENTAL EVOLUTION OF A LACUSTRINE SYSTEM. The palaeoenvironmental evolution of the Loma Negra section (Bardenas Reales de Navarra, Ebro Basin) during the lower—middle Miocene, is studied for the first time. The paleoenvironmental interpretation is based on the recovered ostracod assemblages and the sedimentology. The lower part of this section is composed by red, yellow and grey mudstones, and with Paralimnocythere sp. as the most abundant ostracod taxon. The lithological features and the faunistic assemblage allows the interpretation of a paleoenvironment with the development of shallow water bodies with stagnant, warm and fresh to oligohaline waters in distal alluvial flood plains for this section. The presence of some sandstone levels where the most abundant ostracod species is Cyclocypris laevis (Müller) marks punctual higher energy events inside this alluvial system and the presence of more saline waters. The upper part of the section is formed by grey limestones with interbedded fine grey mudstones. In this interval, Pseudocandona parallela Müller is the most abundant ostracod species, indicating the development of a stable lacustrine system with water currents, and temperate to cold and oligohaline to mesohaline waters. The transition between the alluvial and the lacustrine systems shows a gradual evolution.