The branchiopods display a broad range of reproductive modes, including dioecy, hermaphroditism and parthenogenesis. An order within Branchiopoda, Spinicaudata or the “clam shrimp” are also reported to have all three of these breeding systems; yet parthenogenesis has only been inferred on the basis of a lack of males in several clam shrimp species. Herein we report a detailed analysis of the breeding system of one of these supposed parthenogenetic clam shrimp: Cyzicus gynecia (Mattox, 1950). A RAPD genetic analysis across a three state geographic range (New Jersey, Massachusetts, and New York) showed high levels of genetic differentiation among populations indicative of reproduction without males. Additionally, functional male gametes were found to be produced in a small region of the gonad located just posterior to the head. Thus, we posit that the purported parthenogenetic females of C. gynecia are instead functioning hermaphrodites that produce a small amount of sperm anteriorly in an ovotestis that they then use to fertilize their own eggs. These findings suggest that there are, in fact, no parthenogenetic species within Spinicaudata, but rather all “female” species are most likely self-compatible hermaphrodites.