Sclerite fusion in the problematic early Cambrian spine-like fossil Stoibostrombus from South Australia

New collections of the problematic spine like fossil Stoibostrombus crenulatus Conway Morris & Bengtson from the Mt. Scott Range and Wilkawillina Gorge in the central Flinders Ranges, South Australia contain fused sclerite composites. In each fused specimen the spines are merged along their lateral margins and the orientation of the spines is almost identical. These new specimens confirm that Stoibostrombus spines were dermal sclerites, arranged in lateral pairs or transverse rows. The nature of the animal secreting the spines remains elusive, but available evidence suggest that it was an ecdysozoan animal, possibly a palaeoscolecid worm.