Article: Cardioceratid and kosmoceratid ammonites from the Callovian of Yorkshire

New stratigraphic evidence and systematic revision, including the designation of types where necessary, establish unambiguously the definitions and precise ages of a number of classical species of ammonites which, although in part rare in this country, are of great importance in understanding the evolution of the Boreal and Sub-boreal families Cardioceratidae and Kosmoceratidae. They include Pseudocadoceras boreale Buckman, 1918, Chamoussetia funifera (Phillips, 1829), Chamoussetia phillipsi = nom. nov. pro Ammonites lenticularis Phillips, 1829, non Young and Bird 1828, Longaeviceras placenta (Leckenby, 1859), Quenstedtocerasflexicostatum (Phillips, 1829) and Kosmoceras rowlstonense (Young and Bird, 1822). Five new specific names are introduced: Chamoussetia phillipsi nom. nov., C. buckmani and C. saratovensis spp. nov., Pseudocadoceras grewingki whithami subsp. nov., and Longaeviceras polonicum sp. nov.