Upper Aalenian and Lower Bajocian (Middle Jurassic) Hammatoceratinae (Ammonitina) of the Wutach area (SW Germany)

Ammonites of six genera of the subfamily Hammatoceratinae are reported from the Upper Aalenian and Lower Bajocian of the Wutach area (SW Germany): Accardia, Ceccaites, Pseudaptetoceras, Eudmetoceras, Euaptetoceras, and Fissilobiceras. In the Bradfordensis Subzone (Bradfordensis Zone, Upper Aalenian), the majority of the rare records of Hammatoceratinae is clustered around Ceccaites sieboldi (Oppel, 1862). In the basal Discites Zone (Lower Bajocian), the Eudmetoceras – Euaptetoceras plexus, which has its root in the ancestral genus Pseudaptetoceras, is somewhat more common. After the Hammatoceratinae are completely absent in the middle and upper Discites Zone, they suddenly reappear in the above following Ovale Zone (Lower Bajocian) with the genus Fissilobiceras even as a predominant element of the ammonite assemblages. These gaps in the record indicate that Hammatoceratinae did not live permanently in the Jurassic sea of present-day SW Germany, but immigrated sporadically from the Tethys. This was made possible by newly opening marine connections or by favourable currents. One new species, Fissilobiceras franzi n. sp., is introduced.