Muscle attachment impressions in an Upper Cretaceous ammonite, Diplomoceras notabile Whiteaves, consist of a pair of bean-shaped retractor muscle impressions on the dorsal (antisiphonal) side, and a single, nearly round, impression on the venter, the origin and function of which is not known. The muscular attachment system in D. notabile appears to differ from the typical nautiloid attachment system in lacking a continuous annular elevation and in having a single ventral attachment impression.

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