Oelandiella, the earliest Cambrian helcionelloid mollusc from Siberia

The helcionelloid molluscs Oelandiella korobkovi and O. sibirica Vostokova are redescribed on the basis of type material from the lowest Cambrian of northern Siberia. Oelandiella is reinstated as a recognizable genus separated from Latouchella Cobbold, of which it has been considered generally to be a junior synonym, by differences in the prominent comarginal plication. The bilaterally symmetrical shells of both of these genera are readily delimited from Oelandia Westergard, originally described from the Middle Cambrian of Sweden, which has a characteristic asymmetrical alternation of plicae.