Many were long misidentified as the polychaete annelid Spirorbis until studies of shell microstructure and formation showed significant differences (Taylor and Vinn, 2006).
Spirorbis was once thought to have a fossil record extending back into the Early Paleozoic, but now all pre-Cretaceous spirorbins are known to be microconchids.
They discovered that the “Spirorbis” fossils found in sedimentary strata, including the Joggins and other Carboniferous coal measures, deposited from the Ordovician to Triassic periods are the remains of an extinct order of lophophorates (now called microconchids) unrelated to modern marine tube worms (Annelids) to which the genus Spirorbis belongs.