-TAPHONOMY OF THE FOSSIL MAMMALS ASSEMBLAGE OF THE "1968 FISSURE", SÃO JOSÉ DE ITABORAÍ BASIN, RIO DE JANEIRO STATE, BRAZIL. Significant amount of taxonomic information has beenextracted from fossil mammal assemblages of the São José de Itaboraí Basin, located at Rio de Janeiro State, Southeastern Brazil. However, taphonomic analysis, which are important for understanding the formation of these taphocoenosis, are rare and superficial. A limestone fissure excavated in 1968 (here called "1968 Fissure") stands out among the several known fossiliferous concentrations by its abundance of skeletal elements and by the unique brownish color of the specimens, which differentiate them from those collected in other fissures. This study aims to identify and interpret taphonomic features observed in the taphocoenosis "1968 Fissure", which include fractures, abrasion marks, desiccation marks, teeth marks, bone representativeness, and preservational patterns diagnostic for the occurrence and type of transport during the formation of fossiliferous concentration. Based on taphonomic analysis, the mammal taphocoenosis of the "1968 Fissure" is characterized as parautochthonous, being exposed for a short time before being deposited in the fissure after a short transport, possibly triggered by floods. Probably, predators did not influence the formation of the fossil assemblage studied. Only small mammals occur in the fissure due to a possible selection during the bioestratinomic phase. During the fossildiagenetic phase, several fractures were produced in the material due to compression generated by sediment deposition in the fissure. The observed pattern in the skeletal completeness shows the influence of anatomical features of mammals in differential preservation of skeletal remains during the process of fossilization.Key words: taphonomy, "1968 Fissure", São José de Itaboraí Basin, mammals, Itaboraian mammal age.RESUMO -Quantidade significativa de informações taxonômicas tem sido extraída das assembleias fossilíferas de mamí-feros da bacia de São José de Itaboraí, situada no Estado do Rio de Janeiro. Porém, análises tafonômicas, importantes para o conhecimento da formação dessas tafocenoses, são raras e superficiais. Dentre as várias assembleias fossilíferas desta bacia destaca-se a procedente de uma fenda escavada em 1968 (denominada "Fenda 1968"), pela abundância e pela coloração marrom dos elementos esqueletais, que os diferencia dos fósseis procedentes das demais fendas. Este estudo tem como objetivo a identificação e interpretação de feições tafonômicas observadas na tafocenose da "Fenda 1968", as quais incluem fraturas, marcas de desgaste, de dentes e de dessecação, representatividade óssea, além de padrões preservacionais diagnós-ticos para a ocorrência e o tipo de transporte durante a formação desta concentração fossilífera. Com base na análise tafonômica, a tafocenose da "Fenda 1968" caracteriza-se como parautóctone, tendo ficado exposta por pouco tempo antes de ser depositada no interior da fenda por um curto tr...