‘Nodibeyrichia jurassica’ and associated beyrichiacean ostracode species and their significance for the correlation of late Silurian strata in the Baltic and Britain

Taxonomic revision reveals that the beyrichiacean ostracode ‘Nodibeyrichia jurassica’ can no longer be regarded as an index species for the uppermost (late P’idoli) ostracode ‘zone’ of the Silurian of the Baltic region embracing Estonia, Latvia and Baltic-floor derived erratic boulders. The taxon Nodibeyrichia jurassica Sarv, 1968 (non Gailite 1967) is regarded as a junior subjective synonym of Beyrichia protuberans Boll, 1862. Moreover, the material hitherto assigned to ‘Nodibeyrichia jurassica’ is herein considered to belong to two species: Nodibeyrichia protuberans (Boll, 1862) and Nodibeyrichiu uerrucosa Shaw, 1969. N. uerrucosa occurs in England and Estonia, in the basal part and upper part of the P’idoli Series respectively. N. protuberans, as herein restricted, can be used to recognize the late Piidoli, uppermost ostracode assemblage level (N. jurassica Zone of previous literature) of the Silurian only in the central East Baltic (Latvia) and in erratic boulder material found in southern Baltic areas