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a b s t r a c tFossils of terrestrial mammals preserved in submarine environment have been recorded in several places around the world. In Brazil such fossils are rather abundant in the southernmost portion of the coast, associated to fossiliferous concentrations at depths up to 10 m. Here is presented a review of such occurrences and the first record of fossils in deeper areas of the continental shelf. The fossils encompass several groups of both extinct and extant mammals, and exhibit several distinct taphonomic features, related to the marine environment. Those from the inner continental shelf are removed and transported from the submarine deposits to the coast during storm events, thus forming large konzentrat-lagerstätte on the beach, called "Concheiros". The only fossils from deeper zones of the shelf known so far are a portion of a skull, a left humerus and of a femur of Toxodon sp. and a lower right molar of a Stegomastodon waringi, all collected by fishermen at depths around 20 m. The presence of fossils at great depths and distances from the present coastline, without signs of abrasion and far from areas of fluvial discharges does indicate that these remains have not been transported from the continent to the shelf, but have been preserved directly on the area that today correspond to the continental shelf. These remains indicate the existence of large fossiliferous deposits that have developed during periods of sealevel lowstand (glacial maxima) and have been submerged and reworked by the sea-level rise at the end of the last glaciation.

The objective of the present work is to compare the presence of Pleistocene vertebrate fossils from the central and southern sectors of the Coastal Plain of Rio Grande do Sul, quantifying and qualifying the taphonomy, and taxonomic group and skeletal remains representativeness. A total of 2,820 fossils was collected, among them 95% were collected in the southern sector and 5% in the central sector. In both sectors were identified two populations of bioclasts: non-identified fossils (85%) and identified fossils (15%). The same taxonomic groups and skeletal remains were identified in both sectors, except for some due to the different amount of fossils collected. The two populations of bioclasts identified represent greater (85% non-identified) or less (15% identified) reworking by waves. The hypothesis for the different amount of fossils collected is the availability of fossils on the shoreface and inner continental shelf. The presence of several submerged sedimentary rocks and records of paleolagoons and paleochannels on the shoreface and inner continental shelf of the southern sector indicates probably the source-areas where the skeletal remains were once fossilized and now are being eroded.

The present work describes the taphonomy of the extinct mammals’ fossils (Pleistocene megafauna) found in Chuí creek embankment, in Rio Grande do Sul State, southern Brazil and compares them to the mammals’ fossils occurring along the shoreline of the same State. These mammals lived during the Upper Pleistocene (Lujanense land-mammal period) about 120000 years ago; the fossils that occurs along Chuí creek and the ones found along the shoreline suffered deposition in coastal lagoons, originated during events of sea transgression-regression, althought the last ones are now found in subaquatic environments, preserved in submerged biodetritic banks along the coast and are being thrown onto the beach during storm events. These fossils are extremely hard and dark, due to substitution of the bone’s original calcium phosphate by silicates and oxides. While these fossils are found fragmented on the beach due to wave action and transport, the fossils occurring along Chuí creek embankment are well preserved, indicating that they haven’t suffered significant transport; the latter show light colour and more fragility due to lixiviation. Articulated parts of mammals are found, and many bones show grooves and scratches, suggesting the action of scavengers after death. They are found in situ at a depth of 2,5-3,5m in lacustrine sediments of Pleistocene origin in the Chuí creek embankment and above a layer of oxidated beach sands which show parallel stratification and galleries of the Callianassa crustacean.