Summary

Ammonites that preserve evidence of their soft anatomy or gut contents are exceedingly rare. An example of the Toarcian ammonite, Dactylioceras, with tightly packed fish scales in the supposed position of the stomach, plus further scales and three articulated fish vertebrae in the approximate position of the crop, is described. The body-chamber is largely filled with fine sedimentary rock, but shows several thin areas now lined with diagenetic calcite where the sediment was unable to penetrate. These are interpreted as the positions of ammonite soft tissue because they line parts of the body-chamber, which is consistent with the idea that the stomach and crop remained intact long enough for their contents to be preserved in place. Inquilinism is thought unlikely as an explanation because the fish remains are largely disarticulated and packed together in the rear of the body-chamber, but the fish debris could represent food of an animal that sheltered within the dead ammonite shell. Equally, passive fill of the body-chamber with sediment containing fish scales seems unlikely due to the local concentration at the rear of the body-chamber. Possibly this Dactylioceras ate fish either as a predator or scavenger.

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