Mats Eriksson

The Ordovician jawed polychaete annelid Rhytiprion magnus has hitherto been recorded in erratic boulders of probable East Baltic provenance and in drill cores from Poland and North Estonia. In this study the stratigraphical range and geographical distribution are extended as R. magnus is recorded from the Silurian of Gotland (Sweden) and Indiana (U.S.A.). Hence, R. magnus is now known from the Middle Ordovician to the middle Silurian (lower Ludlow; Kockelella v. variabilis conodont Zone) and comprises one of the few Palaeozoic polychaete species with a documented intercontinental distribution. The species is generally very rare but is abundant at a few localities; on Gotland, in the offshore setting of the Late Wenlock (K. ortus absidata conodont Zone; Colonograptus? praedubeli graptolite Zone) Djupvik Member of the Halla Formation. The distribution pattern shows that R. magnus thrived in low energy, distal platform environments, in which marly and muddy terrigenous sediments accumulated.