A scratch circle origin for the medusoid fossil Kullingia

Kullingia is considered a key taxon in demonstrating the presence of terminal Proterozoic-early Cambrian chondrophorine hydrozoans. However, Kullingia concentrica from the Lower Cambrian of northern Sweden possesses several features that show that it is not a body fossil but that it was formed by current or wave-induced rotation of an anchored tubular organism, possibly a sabelliditid. A scratch circle interpretation applies also to several other reports of Lower Cambrian Kullingia, including Kullingia delicata from the Chapel Island Formation of Newfoundland. Given the considerable number of problematic fossils that have been interpreted as chondrophorines, it is difficult to put an age on the oldest fossil chondrophorines, but it may be as late as the Devonian. Overall, scratch circles appear to be rarely preserved. The occurrence of these scratch circles in Lower Paleozoic storm deposits is probably related to low levels of bioturbation that enhanced both the likelihood of formation and preservation of these structures.