Two ammonoid assemblage biozones, the Fascipericyclus-Ammonellipsites Zone (revised) and the newly proposed Bol-
  landites - Bollandoceras Zone, can be recognized in mid-Dinantian strata from every continent except Antarctica and
  South Arnerica.  During the mid-Dinantian, ammonoids inhabited temperate and tropical seas between the palaeo-
  latitudes 50'N and 50'S.  Over thirty ammonoid genera, including Polaricyclus n. gen., are represented in these bio-
  zones; particularly rich faunas are present in Europe.  Relatively rapid generic turnover occurs near the base of the
  Moliniacian Stage (late Tournaisian), near the Tournaisian/Viséan boundary, and within the early Viséan close to
  the entry of primitive archaediscid foraminifers.