A new species of Calanoid copepod, Rhacodiaptomus besti, is described from material collected in the Igarapé São Pedro, Rio Jamari, State of Rondônia, and Lago Amanã, Rio Japurá, State of Amazonas, in Western Amazonia. A detailed morphological analysis of the species was undertaken in order to provide a basis for future studies on inter and intrageneric relationships.
Calanoid copepod; Rhacodiaptomus; Amazon Basin; Brazil