Reinterpretation of the lower Ordovician conodont apparatus Paroistodus

The lower Ordovician conodont genus Paroistodus has previously been interpreted as a two-element apparatus, although with wide variation among its 'drepanodontiform' elements. Collections of conodonts from a series of Swedish sections include almost 75 000 elements of four successive species of Paroistodus: P. numarcuatus from the upper Tremadoc, P. proteus from the uppermost Tremadoc and lowermost Arenig, P. parallelus from the lower Arenig, and P. originalis from the lower middle Arenig to the lower Llanvirn. These species are probably those best known of the genus, and it is shown here that they all have a seven-element apparatus, closely comparable to that of Drepanodus.