worms in its own genus Wiwaxia corrugata, citing similarities to the Aphroditidae and Polynoidae. In 1966 and 1967, a team led by Harry B. Whittington revisited the Burgess Shale and found so many fossils that it took years to analyze them all. 464 complete specimens of Wiwaxia are known from the Greater Phyllopod bed, where they comprise 0.88% of the community. Eventually in 1985 Simon Conway Morris, then a member of Whittington's team, published a detailed description and concluded that Wiwaxia was not a polychaete. All the known specimens came from in and around the Burgess Shale until 1991, when fragmentary fossils were reported from Australia's Georgina Basin. In 2004 additional finds which may represent two different species were reported from the same area. Articulated specimens are known from Cambrian Stage 3 of Xiaoshiba, China; fragmentary specimens have also been found in the Chengjiang, Cambrian Series 2 deposits in Guizhou, China, and in China's lowermost Miaolingian beds of the Kaili Formation, in the Middle Cambrian beds of the Tyrovice Member, Buchava Formation of the Czech Republic, in the Lower Cambrian Mount Cap formation (Mackenzie Mountains, Canada), in the Emu Bay Shale of Kangaroo Island, South Australia, upper Botomian Stage of the Lower Cambrian, and in the Middle Botomian Sinsk Biota of Siberia, Russia. Isolated sclerites are also common in the small carbonaceous fossil record. Taken together, these finds show that Wiwaxia had a truly cosmopolitan distribution, occurring at all palaeolatitudes and on most palaeocontinents. The Chinese material was originally considered to represent a separate species; like W. corrugata, it possessed spines and regions of sclerites (although it is only known from disarticulated remains), but the sclerites bear a higher density of ribs, and there are two distinct thicknesses of rib (i.e. larger and smaller). At a microscopic level, the sclerites do not differ from Burgess Shale or Mount Cap sclerites, but the Chinese material seems to have developed spines from an early age, distinguishing it from the W. corrugata''. The knob-bearing sclerites from all three localities seem to belong to a different species, and a further species is represented in the Xiaoshiba deposits. What is surprising is the limited variety exhibited between species: all have a fundamentally equivalent scleritome, displaying a notable degree of morphological stasis for some 15 Ma. Isolated spines are more common than sclerites in localities with a poor preservation potential, suggesting that the spines were more