New data on Early Cretaceous (Hauterivian-Barremian) heteromorphic ammonites from northern Germany

The stratigraphic ranges and systematics of heteromorphic ammonites from Lower Cretaceous (Hauterivian-Barremian) deposits in Lower Saxony, northern Germany, are revised. Nine genera and fortyseven species of the family Ancyloceratidae Gill, 1871, are described. One genus (Fissicostaticeras) and 20 species are new; Emericiceras ressense, E. sornayiforme, E. serpentinum, E. subtilicostatum, E. gotti, E. hannoverense, E. kemperi, Crioceratites hastensis, C. subisocostatus, C. vermiformis, Fissicostaticeras claviferum, F. aequicostatoides, F. rarocinctoides, Paracrioceras kleini, Acrioceras (Acrioceras) sarstedtense, A. (A.) crassicostatum, A. (A.) aegidii, A. (A.) longum, A. (A.) astrictum and Uhligia aegidii.