Article: Early Jurassic gastropods from England
Twenty-five gastropod taxa are reported from the Early Jurassic (Hettangian to Toarcian) of England. Of these, 14 are identified to species level, and the remaining 11 are treated in open nomenclature. One genus (Lensataphrus) and six species are introduced as new. The new species are Lensataphrus tatei, Lensataphrus tenuis, Tricarilda toddi, Cylindrobullina dorsetensis, Cylindrobullina ventricosa and Consobrinella greeni. The following new combinations are introduced: Cassianopsis hebertana (d’Orbigny, 1852) for Neritopsis hebertana; Cryptaulax abscisum (Terquem and Piette, 1868) for Cerithium abscisum; and Cylindrobullina avena (Terquem, 1855) for Striactaeonina avena. Most of the genera and some of the species are also known from Central Europe (Germany and France). Typical vetigastropod genera that are present in England and Central Europe are Colpomphalus, Costataphrus, Ooliticia, Eucycloscala and Eucycloidea. The caenogastropod genera Levipleura and Cryptaulax are present in both regions, as are the heterobranchs Tricarilda and Cylindrobullina. The heterobranch genus Consobrinella is reported from England for the first time. Gastropods seem to follow the diversity trends of other marine invertebrates during the Early Jurassic. They diversify until the Late Pliensbachian but decrease sharply in number around the Pliensbachian–Toarcian boundary. This may reflect both regional anoxia and a global mass extinction event in the Early Toarcian.