New records of rare ammonite species from the Inferior Oolite Formation (Middle Jurassic, Aalenian and Lower Bajocian) of Dorset

Abstract

Rare ammonite species are reported from the Inferior Oolite Formation of Dorset. In the Aalenian the ammonite Shahrudites is described from the Scissum Zone for the first time and Malladaites is recorded from the Murchisonae Zone. Tmetoceras regleyi occurs in the Scissum and Murchisonae zones and Tmetoceras henriquesae is described from the Concavum Zone. In the Lower Bajocian, specimens of Zurcheria are presented from the Discites Zone. A revised zonal scheme is used for the Aalenian Stage and two new biohorizons are introduced. The Leioceras subglabrum biohorizon is erected in the Opalinum Subzone and Leioceras evolutum in the Bifidatum Subzone.