Wiwaxia corrugata is an extinct species of animal known only from fossils found in Canada's Burgess Shale deposits. Although Wiwaxia resembles a mollusk in having a well developed radula, it does not really fit the conchifera because of its sclerites (armor of flattened, chitinous spines), but rather the class Aplacophora. The actual classification of Wiwaxia in the animal kingdom is still controversial.

Wiwaxia has recently been proposed as an annelid or at least a close relative of one. The first breakthrough in establishing Wiwaxia's affinities came from a postgraduate paleontologist at Harvard who was inspired by Stephen Jay Gould's lectures a decade or so ago. This young researcher, Nick Butterfield, managed to extract pieces of the scalelike armour from the fossilized animal. When Butterfield studied their microstructure, he noticed immediately that it was the same as that of the chitinous bristles (chaetae) that project from the bodies of such modern annelids as earthworms. His conclusion, published in 1990, was that Wiwaxia was not a mollusk at all but an annelid. Butterfield's view has however recently been challenged by the Danish zoologist Danny Eibye Jacobsen (2004) who, after detailed studies of all available material of Wiwaxia, convincingly demonstrated that there are no characters clearly placing Wiwaxia with the annelides. A placement with the molluscs therefore still seems most likely.

References

• National Museum of Natural History (2005) Wiwaxia corrugata. Retrieved on Oct. 26, 2005.

Fossils

Wiwaxia