The ammonite faunas of the English Portland Beds and the zones of the Portlandian Stage

Abstract

On the basis of new and large collections of ammonites, a succession of ammonite faunas is described from the Portland Beds of southern England and a revised scheme of Standard Zones (=chronozones) proposed. The faunas of the Portland Freestone of Dorset are shown to consist largely of hitherto undescribed species; Titanites anguiformis sp. nov. is described and figured therefrom. Correla­tions are proposed with other areas where the Portland Beds occur, and the scheme is integrated with the zonal scheme proposed by Casey (1974) for the younger Portlandian faunas. Glaucolithites glaucolithus Buckman and Titanites giganteus (Sowerby) are redefined with the aid of new material. 'Portlandian' is preferred as stage name for the terminal Jurassic stage.