As in 1990, he argued that Wiwaxias sclerites were internally much more like the bristles of polychaete annelids such as Canadia than like any forerunner of molluscan shell plates; since a 2005 paper had downplayed this argument with the comment that similar bristles also appear in molluscs and brachiopods, he pointed out that modified bristles appear as a covering over the back only in polychaetes and hence Wiwaxias sclerites should indeed be regarded as like polychaetes' bristles.
In 1990, he argued that Wiwaxias sclerites were internally more similar to the bristles of polychaete annelids like Canadia than any precursor to mollusc shell plates; since a 2005 paper downplayed this argument by stating that similar bristles also appear in molluscs and brachiopods, he pointed out that modified bristles are only found as a covering over the back in polychaetes, hence Wiwaxias sclerites should be considered like polychaete bristles.