Lower Homerian (Silurian) Pristiograptus from the Zdanow section, Bardo Mountains (Sudetes, Poland) and their palaeobiogeographical implications

Pristiograptus dub/us pseudodubius and Pristiograptus lodenicensis were collected from outcrops of black pelagic shales of the Zdanow section of the Bardo Mountains (Sudetes, Poland). The species are easily distinguished from one another in that P. lodenicensis has distinct lobate processes on its thecae, whereas those of P. d. pseudodubius are comparatively unornamented. Our findings indicate that the age of the Lower Graptolitic Shales in the Zdanow is the middle part of the C. lundgreni graptolite Hiozone (lower Homerian, upper Wenlock). The presence of P. d. pseudodubius at this site adds another locality to its global range, while the presence and abundance of P. lodenicensis further indicates the restriction of the latter species to the Rheic palaeo-ocean.