Ammonites from the Lias Group (Lower Jurassic, Sinemurian and Pliensbachian) of White Park Bay, Co. Antrim, Northern Ireland

Northern Ireland's Jurassic succession has received relatively little detailed investigation. Late Sinemurian and early Pliensbachian strata are present in parts of north Antrim but they are poorly exposed at outcrop and have been penetrated by just a single borehole, at Portmore, in which parts of the succession are missing. Collecting from White Park Bay over more than two decades, augmented by examination of museum material, has established the presence within the Rathlin (North Antrim) Basin of ammonite zones and subzones additional to those proven in the Portmore Borehole. This suggests that parts of the Sinemurian and Pliensbachian stages, from the Obtusum Zone through to the Davoei Zone, and possibly even higher, may be preserved in onshore or nearshore parts of the basin. Despite the generally poor exposure, the material recovered encompasses more than 40 ammonite species, including several taxa that are poorly represented elsewhere in the UK, of which two, Vicininodiceras dalriatense sp. nov. and Cheltonia howarthi sp. nov., are previously undescribed.