The branchiopod family Chydoridae is present in many freshwater ecosystems, and chydorids are an important and significant component of aquatic food webs. These cladocerans are diverse and abundant, and provide an important link between primary producers and secondary consumers. They make good long-term ecological indicators due to their diversity, abundance, specific habitat requirements and good preservation in sediments. Taxonomy of the family Chydoridae in Australia is confounded in that many species identified early this century (and indeed more recently) were not described adequately, nor discriminated sufficiently from their Northern Hemisphere counterparts. Cosmopolitan species were predominately recognized but recent studies have demonstrated that some of these taxa in Australia are morphologically distinct from the nominate (Northern Hemisphere) species. It is now evident that there are unique Australian chydorid assemblages, with evidence of both continental regionalism within Australia, and strong Gondwanan affinities.