Data from: Ontogeny, morphology and taxonomy of the soft-bodied Cambrian ‘mollusc’ Wiwaxia

The soft-bodied Cambrian organism Wiwaxia poses a taxonomic conundrum. Its
imbricated dorsal scleritome suggests a relationship with the polychaete
annelid worms, whereas its mouthparts and naked ventral surface invite
comparison with the molluscan radula and foot. 476 new and existing
specimens from the 505-Myr-old Burgess Shale cast fresh light on
Wiwaxia's sclerites and scleritome. My observations illuminate the
diversity within the genus and demonstrate that Wiwaxia did not undergo
discrete moult stages; rather, its scleritome developed gradually, with
piecewise addition and replacement of individually secreted sclerites. I
recognize a digestive tract and creeping foot in Wiwaxia, solidifying its
relationship with the contemporary Odontogriphus. Similarities between the
scleritomes of Wiwaxia, halkieriids, Polyplacophora and Aplacophora hint
that the taxa are related. A molluscan affinity is robustly established,
and Wiwaxia provides a good fossil proxy for the ancestral aculiferan –
and perhaps molluscan – body plan.