The mid-Late Devonian pelagic sedimentary successions of the Rhenish Mountains and other regions show a double
  black shale horizon called the annulata Black  Shale. lt marks, at the species level, a prominent faunal turnover of
  ammonoids from the Prolobites delphinus Zone into the Platyclymenia annulata Zone.  An analysis of ammonoid genera        distribution, phylogenetic relationships, and morphospace occupation demonstrates that the "annulata Event" does not        correspond to a crisis of the group and does not fulfill the criteria of a major biotic event.