Article: The diet of the early Toarcian ammonite Harpoceras falciferum

Diagenetically compressed ammonites from the Early Toarcian Posidonienschiefer in southern Germany yield new data on the diet and ingestion regulation of ammonites. About 4 per cent, of the relatively large body chambers of adult Harpoceras falciferum macroconchs contain distinctive food remains, mostly pereiopods of small decapod crustaceans, which probably were the main prey of this ammonite species, and rarely abdomens and telsons of the same crustaceans or aptychi of small ammonites. The contents of the digestive tract are preserved in the adapical three-quarters of the body chamber as a row of 'food balls'. The number of these food balls is variable; up to five have been counted. In most specimens it is not possible to distinguish between crop and stomach contents.About 1 per cent, of adult Harpoceras falciferum macroconchs contain bivalve debris in their body chamber. Although in some specimens this may represent the crop content of the ammonite, in the majority of specimens the debris may be interpreted as food remains not of the ammonite itself, but of another animal living in the mantle cavity area of dead ammonites.