The caviomorph rodents are scarcely known from the Quaternary record of Rio Grande do Sul State, Brazil. This work deals with caviomorphs from two sites, with datings including the Early to Late Holocene. The taxa recorded were: Cavia sp., C. aperea, C. magna, Ctenomys sp., Phyllomys sp., Myocastor coypus, Euryzygomatomys mordax, Dicolpomys fossor, the last two of which are extinct. A new fossil species, Clyomys riograndensis sp.nov. is also described. The stratigraphic distribution of these taxa allows us to suggest a slow and gradual climatic change during the Holocene and a mosaic environment with grasslands and gallery forests, which is indicated by the presence of fossorial animals that typify open areas, coexisting with taxa of forested areas.

SMALL MAMMALS DIVERSITY (DIDELPHIMORPHIA AND RODENTIA) FROM THE HOLOCENE OF NORTHEASTERN RIO GRANDE DO SUL STATE, SOUTHERN BRAZIL: TAXONOMIC AND PALEOENVIRONMENTAL IMPLICATIONS. Despite the increase in knowledge about small mammals from the Holocene of Rio Grande do Sul State and their importance as paleoenvironmental indicators, most assemblages from archaeological sites remains without a detailed analysis. This paper studies the rich small mammals content recovered from the archaeological site RS-C-61: Adelar Pilger, Harmonia, which shows evidence of continuous human occupation throughout the Holocene, from about 8,000 years BP to 3,000 years BP. The assemblage of this site is composed of 25 taxa, including fi ve didelphid marsupials, 15 cricetid and fi ve caviomorph rodents. Most marsupials are also registered in two other sites, Afonso Garivaldino Rodrigues and Sangão. Among Cricetidae, Gyldenstolpia, Kunsia and Oxymycterus are fi rst recorded for Quaternary of Rio Grande do Sul State. On the other hand, the caviomorph assemblage of Pilger site is less diverse than those of the Afonso Garivaldino Rodrigues and Sangão sites. Pilger site includes both small mammals of open (e.g. Thylamys, Calomys, Cavia) and forest (Delomys, Sooretamys and Phyllomys) environments, also supported by palynological data. Three caviomorph (Euryzygomatomys mordax, Dicolpomys fossor and Clyomys riograndensis) are extinct and, compared to the recent fauna of seasonal forest of Rio Grande do Sul, three other taxa (Gyldenstolpia sp., Kunsia tomentosus and Pseudoryzomys simplex) suff ered regional extinctions.

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-HOLOCENE SIGMODONTINE RODENTS (MAMMALIA, RODENTIA, CRICETIDAE) FROM RIO GRANDE DO SUL, BRAZIL -THE SITE RS-TQ-58: AFONSO GARIVALDINO RODRIGUES. We present the sigmodontine assemblage from lower and middle Holocene recorded in the archaeological site RS-TQ-58: Afonso Garivaldino Rodrigues (County of Brochier, State of Rio Grande do Sul). A total of 16 species are detected from the study of 572 specimens, about half of which belonging to the tribe Akodontini. The assemblage recorded include species which typically inhabit open areas (e.g. Calomys sp., Gyldenstolpia sp., Kunsia tomentosus) and also several considered as forest dewellers (e.g. Delomys sp., Juliomys sp., Sooretamys angouya). Necromys obscurus, a sigmodontine today restricted to Central Argentina and Southern Uruguay, is abundantly recorded in Garivaldino and reported for the first time to the Quaternary from Brazil. Thaptomys nigrita and Wilfredomys oenax have in Garivaldino their first records to the Holocene from Rio Grande do Sul State. Compared to the recent assemblage of sigmodontine rodents recorded in Rio Grande do Sul, Pseudoryzomys simplex, K. tomentosus, N. obscurus and Gyldenstolpia sp. became regionally extinct. The sigmodontine assemblage detected in Garivaldino is richest than a previously studied one from Pilger site. The evidence of both sites reflects changes in the species composition, which can be linked with a progressive transformation of the general landscape from mostly open grasslands to forests. Key words: lower Holocene, Necromys obscurus, Sigmodontinae, Thaptomys nigrita, Wilfredomys oenax.RESUMO -Apresentamos a assembleia de sigmodontíneos do Holoceno inferior e médio registrada no sítio arqueológico RS-TQ-58: Afonso Garivaldino Rodrigues (Município de Brochier, Estado do Rio Grande do Sul). Um total de 16 espécies foram detectadas pelo estudo de 572 espécimes, sendo quase metade destes pertencente a tribo Akodontini. Esta assembleia inclui espécies tipicamente de áreas abertas (e.g. Calomys sp., Gyldenstolpia sp., Kunsia tomentosus) e outras consideradas florestais (e.g. Delomys sp., Juliomys sp., Sooretamys angouya). Necromys obscurus, sigmodontíneo atualmente restrito à Argentina Central e sul do Uruguai, está presente de forma abundante no sítio Garivaldino e é registrado pela primeira vez para o Quaternário do Brasil. Thaptomys nigrita e Wilfredomys oenax tem seus primeiros registros para o Holoceno do Estado do Rio Grande do Sul. Em comparação com a assembleia atual de roedores sigmodontíneos conhecida para o Rio Grande do Sul, Pseudoryzomys simplex, K. tomentosus, N. obscurus e Gyldenstolpia sp. tornaram-se regionalmente extintos. A assembleia de sigmodontíneos registrada no Garivaldino é mais rica do que outra previamente estudada proveniente do sítio Pilger. A evidência de ambos os sítios reflete mudanças na composição de espécies, a qual pode estar relacionada com uma transformação progressiva da paisagem, de campos abertos para florestas. Palavras-chave:Holoceno inferior, Necromys obscurus, Sigmodontin...

In the last few years, studies about climate successions in Rio Grande do Sul State (southern Brazil) during the Quaternary increased significantly, mostly due to palynological studies. The knowledge about Quaternary small mammals from Rio Grande do Sul is very poor. However, among the results obtained by archeological research there is an interesting collection of small mammals exhumated from rock shelter deposits. Here we describe the marsupial fauna found in two sites: Garivaldino and Sanga˜o. Both sites are located at the boundary between two large Neotropical subregions, Chaco and Parana. Sediments from these two sites are from the early, middle, and part of the late Holocene. Additionally, we discuss paleobiogeographic, paleoenvironmental, and paleoclimatic aspects, on the basis of the seven taxa recorded: Gracilinanus microtarsus, G. agilis, Monodelphis americana, Thylamys velutinus, Thylamys cf. T. velutinus, Philander opossum, and Didelphis sp. Paleoenvironmental aspects inferred for both sites are consistent: the emergence of typical elements of the current Parana biogeographic subregion was probably established by the end of the early Holocene or the beginning of the middle Holocene. Conclusions are also coherent with the results previously obtained from palynological sequences in these same localities. The micro-marsupials sequence suggests that the environmental changes were not abrupt but gradual during the Holocene in Rio Grande do Sul State.

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Occurrence of Ophiomorpha nodosa in Pleistocene sediments of Coastal Plain of Pinheira, Santa Catarina, Brazil. The occurrence of Pleistocene (MIS) 5 marine ichnofossils in a locality of the Coastal Plain of Pinheira, State of Santa Catarina is described, and their value as indicators of the geological/stratigraphical evolution in this area is discussed. This sedimentary sequence indicates the transition among the subtidal zone, where the ichnofossils occur, to the supratidal zone, and finally to dunes. The ichnofossils can be seen in vertical view, between 0 and 4.5 m above the present sea level. The galleries are cylindrical structures with circular or oval transversal section, without ramifications. Their interior walls are smooth, and the exterior walls are composed of pellets made of clay and sand homogeneously dispersed, without a specific arrangement. This morphology is related to ichnospecies Ophiomorpha nodosa. The average density was 32.9 galleries/ m², ranging from 22 to 51 galleries/m². The highest density found could be related to time-averaging, or to a deeper subtidal environment. The vertical distribuition of Ophiomorpha and the absence of faciological variations in the deposits might indicate an aggradational stage between the trangressive and regressive phases.