Extremalona timmsi gen. nov., sp. nov., a new cladoceran (Cladocera: Anomopoda: Chydoridae) from an acid saline lake in southwest Western Australia.

A new species of Cladocera, Extremalona timmsi gen. nov., sp. nov., was found in acid saline lakes in the southwest of Western Australia. Extremalona gen. nov. belongs to the Coronatella-branch of Aloninae, but differs from all members of the group by the oval body with small high-set head (tip of rostrum located at half-height of the body), the exopodite III with uniform, well-developed setae 4–6 and male antennule with six lateral and nine terminal aesthetascs, and by numerous other characters. In our opinion, Extremalona gen. nov. is one of the ancestral genera of the Coronatella-branch of Aloninae, sharing numerous common features with the elegans-group of Alona s.l. Our data confirm a high level of endemism in Australian Chydoridae and Cladocera in general. [ABSTRACT FROM PUBLISHER]