A new classification of the branchiopod Crustacea

Abstract

The first satisfactory groupings of the components of the Branchiopoda (Crustacea) were those of G. O. Sars, whose successive refinements, as modified by Caiman in a much used work, received wide acceptance. These schemes, and the more important of the subsequently suggested changes, are listed and tabulated. The Branchiopoda is a morphologically heterogeneous group whose component subgroups share a constellation of primitive features. It is also ancient, with representatives known from as far back as the Devonian, and probably originated in pre-Devonian times, yet still has many extant, sometimes highly successful, representatives. Such a situation presents difficulties to the would-be classifier. A new scheme is proposed which involves the elevation of four lower categories among the so-called Cladocera to ordinal rank. Two conchostracan taxa are also given ordinal status. The ten constituent orders now recognized within the Branchiopoda are defined in more detail than hitherto as a working basis for future investigations.