En este trabajo se describe y analiza la estructura de un ensamble fosil marino macrobentonico del Pleistoceno Tardio (posiblemente ultimo interglacial) en Caleta Patillos, norte de Chile (20°45'S, 70°12'O). Un analisis tafonomico sugiere la existencia de un ambiente de depositacion submareal somero, primariamente de fondo blando, de alta energia, e intensa mezcla de especies desde varios tipos de habitats bentonicos. El total de 38 taxa identificados, correspondientes en su mayoria a especies de moluscos, gastropodos y bivalvos, no fue distinto de lo registrado en otros ensambles pleistocenicos tardios en el norte de Chile. A una escala biogeografica, la composicion del ensamble de moluscos mostro notables similitudes con la fauna actual, y no se registraron especies extralimitales. A una escala local, sin embargo, una comparacion con el ensamble viviente en el mismo sitio de estudio mostro una dramatica alteracion en la composicion de especies, un resultado que no puede ser explicado por sesgos de muestreo. Se plantea una profunda y quizas muy reciente (i.e., en tiempos historicos) alteracion en la estructura de los ensambles macrobentonicos locales.ABSTRACT:In the present study, we describe and analyze the structure of a Late Pleistocene (likely last interglacial) marine macrobenthic assemblage in Caleta Patillos (20°45'S, 70°12'W), northern Chile. A taphonomic analysis suggests the existence of a shallow subtidal paleonvironment, mainly soft-bottom, of high energy and intense mixing from several benthic habitats. The total number of 38 taxa recorded, mainly gastropods and bivalves, was not different than the ones reported in other Late Pleistocene assemblages in northern Chile. At a biogeographic scale, the composition of mo Husk species showed remarkable similarities with present-day fauna, and no extralimital species were recorded. At local scale, however, a comparison with the living assemblage in the same area of study showed a dramatic shift in the species' composition, a result that cannot be explained by sampling bias. A deep and perhaps very recent (i.e., at historical times) alteration of the structure of local macrobenthic assemblages is hypothesized.In the present study, we describe and analyze the structure of a Late Pleistocene (likely last interglacial) marine macrobenthic assemblage in Caleta Patillos (20°45'S, 70°12'W), northern Chile. A taphonomic analysis suggests the existence of a shallow subtidal paleonvironment, mainly soft-bottom, of high energy and intense mixing from several benthic habitats. The total number of 38 taxa recorded, mainly gastropods and bivalves, was not different than the ones reported in other Late Pleistocene assemblages in northern Chile. At a biogeographic scale, the composition of mo Husk species showed remarkable similarities with present-day fauna, and no extralimital species were recorded. At local scale, however, a comparison with the living assemblage in the same area of study showed a dramatic shift in the species' composition, a result that cannot be explained by sampling bias. A deep and perhaps very recent (i.e., at historical times) alteration of the structure of local macrobenthic assemblages is hypothesized.