Although branchipods are often depicted as primitive crustaceans, little is known about the morphology and relationships of the constituent groups. The branchipod taxon Conchostraca, recently split into two orders, is a diverse assemblage of small, bivalved, freshwater crustaceans. The first of the two conchostracan orders (Laevicaudata) was addressed earlier; the Spinicaudata are the focus of this proposal. The goals of the research have been expanded to encompass the entire Branchiopoda, with emphasis on the spinicaudatan families. The proposed research is a three phase project consisting of 1) a thorough morphological treatment of each genus of the four spinicaudatan clam shrimp families (Cyclestheriidae, Cyzicidae, Leptestheriidae, and Limnadiidae); 2) a phylogenetic analysis of the morphological data and employing outgroups in the Cladocera, Anostraca, and Notostraca; and 3) a phylogenetic analysis employing 18S ribosomal RNA sequences from fresh material of all 8 currently recognized branchipod orders. Of the five families previously combined in the taxon Conchostraca, morphological examinations and systematic reviews have been completed of two: Lynceidae and Limnadiidae. A third family (the monotypic Cyclestheriidae) has been carefully examined and found to be invariant and to agree with morphological descriptions made in the last century. Thus, three of the five conchostracan families are completed. This project is to complete the morphological examination and data collection for the two remaining spinicaudatan families ( Cyzicidae and Leptestheriidae) and for the outgroups in the Cladocera, Anostraca, and Notostraca, and to collect fresh material for the rRNA work.
