Spumellarian radiolarians are abundant within lower Silurian concretions that also contain an exceptionally-preserved, non-biomineralized, three-dimensional macrofauna (the Herefordshire Konservat-Lagerstatte). Only the radiolarian tests are preserved; sparry calcite precipitated in the space originally occupied by the cytoplasm. Partial dissolution of the tests occurred during precipitation of the calcite, but more significant, later dissolution created voids that are now infilled by ankerite and clay minerals. Specimens are surrounded by spherical 'cocoons' of quartz, kaolinite, pyrite and, especially, ankerite, the last a product of secondary dolomitization of the sparry calcite. Although there are strong parallels with the taphonomy of the most common element of the macrofauna, the non-biomineralized arthropod Offacohis kingi, uncertainties remain as to the relative timing of the precipitation and/or accumulation of clay minerals that are associated with both taxa. The unusual preservation of radiolarian tests in carbonate minerals impacts negatively on the quality and abundance of specimens recovered using standard micropalaeontological bulk- processing techniques; modified techniques yield a higher number of complete specimens.
