Monograph: Mid-Dinantian Ammonoids from the Craven Basin, North-West England

A major new ammonoid-bearing sequence is described from the Worston Shale Group, which spans the late Tournaisian (early Chadian) to mid-Visean (early Asbian) interval in the Craven Basin of north-west England. The faunas are referable to the Fascipericyclus-Ammonellipsites (FA), Bollandites-Bollandoceras (BB) and lower part of the Beyrichoceras Zone (Bl) ammonoid zones. Particularly significant are the early Visean assemblages from the FA Zone, which are the most diverse known, apart from faunas described previously from the northern Urals of the former Soviet Union. The described assemblages comprise: Ammonellipsites clitheroensis sp. nov., Beyrichoceras aff. obtusum, Beyrichoceratoides in flatus sp. nov., B. sp. aff. komiorum, B. sp. 1, B. sp. 2, Bollandites varians sp. nov., Bo.? sp., Bollandoceras hodderense Bol. micronotum, Bol. sp. 1, Bol. sp. 2, Dimorphoceras leagramense sp. nov., Dzhaprakoceras bellmanense sp. nov., D. catena sp. nov., D. deflexum, D. cf. djaprakense, D. flexum sp. nov., D. hispanicum, D. levis sp. nov., D. paracatena sp. nov., D. subglobosum, D. undulatum sp. nov., D. westheadi sp. nov., Economismoceras planum sp. nov., Helicocyclus divergens sp. nov., Merocanites cf. applanatus, M. quadrilobus sp. nov., Michiganites sp., Nomismoceras rotiforme, Parahammatocyclus chaigleyensis gen. et sp. nov. and Rotopericyclus postremus sp. nov. Existing suprageneric classification is modified; the new superfamily Girtyocerataceae is erected together with two new subfamilies: the Ammonellipsitinae and Pericyclinae. Several genera are reclassified, including Beyrichoceras, transferred from the Anthracoceratidae to the Girtyoceratidae, and Bollandites, transferred from the Muensteroceratidae to the Pericyclinae.