Qingjianglepas from the Qingjiang biota, an evolutionary dead-end of Cambrian helcionelloid mollusks?

Abstract A minute limpet-shaped shell, Qingjianglepas elegans n. gen. n. sp., is reported from the 518 million-year-old Qingjiang biota in Hubei, China. The new shell exhibits a typical limpet morphology with a shell sculpture of strongly developed radial ribs, an anterior shell fold, and distinctive shell shape shift. Feature combinations such as in Qingjianglepas are unique among Cambrian mollusk assemblages, but strikingly resemble that of some modern fissurellids (keyhole and slit limpets; Vetigastropoda). The biological affinity of Qingjianglepas is discussed, but temporarily remains uncertain. Regardless, the heavily sculptured and limpet-shaped Qingjianglepas represents a previously unrecognized shell form, and hence significantly extends the morphological diversity of Cambrian mollusks. The abrupt ontogenetic change in shell morphology suggests that Qingjianglepas might change microhabitat throughout the growth of the animal. This study reveals that the phenomenon of limpetization occurred within early Cambrian total-group conchiferans. Furthermore, Qingjianglepas might represent an evolutionary dead-end in course of helcionelloid mollusk evolution, which marks the end of the Cambrian explosion of animals at the beginning of Cambrian Series 2.