Applied Biostratigraphy

Bivalved Crustacea (related to the modern barnacle but are not attached to any substrate), free swimming but mainly benthonic, very rarely planktonic

geologic range: Cambrian?/Ordovician – Recent (“extant”)

inhabit almost any aqueous environment (even damp woodland leaf litter!) from fresh waters to fully marine (down to abyssal depths)

usually subordinate to other microfossils in terms of numbers recorded

useful in lacustrine oil basins

biostratigraphically significant in particular areas/intervals but subordinate to other fossil groups and therefore has relatively few practicing specialists