†Olcostephanus (Neoastieria) Obata & Matsukawa 1984

Obata & Matsukawa 1984. A Barremian occurrence of an olcostephanid, a perisphinctacean ammonite, from the Choshi Group, Japan. Bulletin of the National Science Museum Series C (Geology & Paleontology), 10(4) 1984: 169-180