Article: Spicule pseudomorphs in a new Palaeozoic chaetetid, and its sclerosponge affinities

A Palaeozoic chaetetid, bearing intramural spicule pseudomorphs. Chaetets (Boswellia) mortoni sp. nov.. is described from the British Dinantian. Spicules are preserved as calcite, pyrite, and silica pseudomorphs. Only silica pseudomorphs retain detail of their tylostyle form. Neomorphism locally obliterates the spicular fabric. A primary mineralogy is suggested consisting of an aragonitic calcareous skeleton, with entrapped opal 'A' spicules. Comparison of morphology and microstructure with extant and fossil sclerospongcs indicales a close relationship between this chaetetid and the Ceratoporellida. and supports the sclerosponge nature of some Palaeozoic chaetetids.