The ammonite assemblage of the planula Biohorizon (Early Kimmeridgian, Planula Zone) is studied in detail, mainly based on bed-by-bed collected specimens from the Wohlgeschichtete-Kalke Formation of the Plettenberg Quarry near Balingen (western Swabian Alb) and some additional specimens from coeval beds of the former Schneider Quarry at Spielberg am Hahnenkamm (southwestern Franconian Alb). Within the Upper Jurassic of Southern Germany, the planula Biohorizon is one of the few well-characterized biohorizons of the Lower Kimmeridgian. Its ammonite assemblage comprises at least 16 ammonite taxa, most of which are typical of the Submediterranean or Mediterranean provinces; only few of them are of Subboreal affinity, whereas Boreal taxa are completely absent.