Specimens of the Late Devonian ammonoid species Erfoudites rugosus sp. nov. from the Rhenish Massif of
  Germany show an additional wrinkled structure that covers the body chamber ornament.  The pattern closely
  resembles the dorsal wrinkle layer known from many ammonoids; the course of the wrinkles is radial, par-
  tially following the growth line course.  This wrinkte structure is interpreted as resulting from a secretion of
  the mantle, which expanded ventrally or dorsally over the conch.