The temperate zone of the southwestern Atlantic Ocean (23-42°S), which includes the Patagonian Shelf Large Marine Ecosystem and the Subtropical Convergence Zone, is one of the most productive areas of the Southern Hemisphere. Key features of this region are a wide continental shelf, the convergence of cold and warm currents, and continental freshwater input of the La Plata River. The Uruguayan marine and estuarine waters are at the core of this zone. The marine and estuarine bivalve fauna of Uruguay has received good attention since the publication of the Voyage of Alcide d'Orbigny (1834)(1835)(1836)(1837)(1838)(1839)(1840)(1841)(1842)(1843)(1844)(1845)(1846). Here we provide an overview of taxonomic, faunistic and b iogeographic issues, identifying knowledge gaps and highlighting priorities for future research. The main threats for that fauna are discussed, with emphasis on species of current or potential socioeconomic interest. Of the 231 species reported from the area, only four species are strictly estuarine: Erodona mactroides Bosc, 1801, Tagelus plebeius (Lightfoot, 1786), Brachidontes darwinianus (d'Orbigny, 1842) and Mytella charruana (d'Orbigny, 1842). All of these have large biomasses, as is also the case for the marine eurihaline Mactra isabelleana d'Orbigny, 1846. A total of 112 deep-sea species (i.e., living deeper than 200 m) are recorded for the region, including almost every known group occurring elsewhere in deep-sea basins, with the exception of sunken wood associated species. Of these, 38 have been recorded only from the Argentine Basin. Some new records are preliminarily reported and discussed, including

The Late Pleistocene marine molluscan assemblage from La Coronilla is one of the richest Quaternary marine deposit from Uruguay. This contribution represents an update of the bivalve and gastropod species composition of this deposit and includes a palaeoecological analysis of the molluscan fauna. The ecological preferences of the recorded species allowed the reconstruction of the palaeoenvironmental conditions of the eastern Uruguayan coast and the palaeobiogeographic scenario of the area during the Late Pleistocene. The fossil assemblage of La Coronilla contains 91 bivalve and gastropod taxa of which 28 are new to this deposit and 11 are first reported for the Uruguayan Quaternary marine assemblages. The latest are Turbonilla abrupta, Turbonilla cf. farroupilha, Turbonilla brasiliensis, Turbonilla cf. deboeri, Turbonilla penistoni, Turbonilla turris, Olivella defiorei, Eurytellina angulosa, Kellia sp., Paraleptopecten bavayi, and Pandora sp. Almost all recorded species from the assemblage are marine and live in soft bottoms, although hard/consolidated substrate species and microgastropods that live in ecological interaction with other invertebrate taxa were also found. The high percentage of tropical-subtropical species, the absence of cold-water species, and the record of extralimital warm water northern species, adds new evidence for the inference of warmer than present conditions in the Uruguayan coast during the Late Pleistocene. ResumoA associação de moluscos marinhos do Pleistoceno Superior de La Coronilla é um dos mais ricos depósitos marinhos Quaternários do Uruguai. Esta contribuição representa uma revisão da composição de espécies de bivalves e gastrópodes deste depósito e inclui uma análise paleoecológica da fauna de moluscos. As preferências ecológicas das espécies registradas permitiram a reconstrução das condições paleoambientais da costa leste uruguaia e do cenário paleobiogeográfico da área durante o Pleistoceno Superior. A associação fóssil de La Coronilla contém 91 taxa de bivalves e gastrópodes, dos quais 28 são novos neste depósito e 11 são relatados pela primeira vez nas associações marinhas quaternárias uruguaias. São elas Turbonilla abrupta, Turbonilla cf. farroupilha, Turbonilla brasiliensis, Turbonilla cf. deboeri, Turbonilla penistoni, Turbonilla turris, Olivella defiorei, Eurytellina angulosa, Kellia sp., Paraleptopecten bavayi e Pandora sp. Quase todas as espécies registradas na associação são marinhas e vivem em fundos constituídos por sedimentos móveis, embora também sejam encontradas espécies de substratos duros/sedimentos consolidados e microgastrópodes que vivem em interação ecológica com outros taxa de invertebrados. A alta percentagem de espécies tropicais-subtropicais, a ausência de espécies de água fria e o registro de espécies que com habitats não limitados às águas quentes do norte, constituem novas evidências da ocorrência de condições mais quentes do que as atuais na costa uruguaia durante o Pleistoceno Superior.