of the mammals from archaeological sites in chaco province, myocastor coypus constituted an important subsistence resource for the human groups that inhabited the area of esteros, ca？adas and selvas de ribera in the late holocene. the aim of this paper is to present the results of materials studies relating to m. coypus from the archaeological sites of el cachapé potrero 5 and sotelo 1 (primero de mayo department, chaco province). chronologically, these sites are located between 1200 and 1690 years bp. the nisp was 7,868 and 4,412 and the mni 251 and 259 for potrero v and sotelo i, respectively, accounting for 84% and 77.1% of all specimens recovered from the two archaeological sites. in addition to quantitative analysis, age profiles and osseous, anthropogenic, and natural modifications were analyzed, identifying the various taphonomic agents that influenced the formation of the samples. m. coypus was of great importance to the subsistence of human groups that inhabited the region. such groups took full advantage of the rodent, using them not only as a food resource but also as a raw material for the manufacture of bone tools and probably also for their hides.