Eocyzicus is defined as those cyzicid spinicaudatans with a round condylus dorso-posteriorly on the head, a wide space between the head and trunk, and the male rostrum spatulate. Furthermore, most if not all species have a dorsal columnar lobe on the posterior-most trunk segments terminating in a single spine. Eocyzicus parooensis Richter and Timms is widespread in Australian inland hyposaline waters, and Eocyzicus argillaquus n. sp. also occurs across the inland but generally in turbid freshwater clay pans. The two species differ morphologically in number of trunk segments, head structure, features of the caudal furcae, and in a number of minor features.