David Bukry Stefan Gartner 1975 <p>The family Ceratolithaceae includes a group of horseshoe-shaped calcareous nannofossils and contains ten species which are assignable to two genera: <i>Amaurolithus</i> n. gen. and <i>Ceratolithus</i>. Species of <i>Amaurolithus</i> are characterized by showing faint or no birefringence in cross-polarized light when viewed in preferred orientation. Included in <i>Amaurolithus</i> are <i>A. amplificus</i> (Bukry and Percival), <i>A. Mzzarus</i> (Bukry), A. delicatus n. sp., <i>A. primus</i> (Bukry and Percival), and <i>A. tricorniculatus</i> (Gartner). Species of <i>Ceratolithus</i> are characterized by their strong birefringence in cross-polarized light when viewed in preferred orientation. <i>Ceratolithus</i> includes <i>C. acutus</i> Gartner and Bukry, <i>C. armatus</i> Miiller, <i>C. cristatus</i> Kamptner, <i>C. rugosus</i> Bukry and Bramlette, and <i>C. telesmus</i> Norris. The family first appears in the geologic record during the late Miocene, represented by the nonbirefringent-appearing species that constitute the genus <i>Amaurolithus</i>. A succession of these species persists into the early Pliocene. The distinctly birefringent forms assigned to the genus <i>Ceratolithus</i> first appear near the base of the Pliocene; the succession has persisted to modern time.</p> application/pdf en U. S. Geological Survey Morphology and phylogeny of the coccolithophycean family Ceratolithaceae article