Article: Pathologically deformed Graphoceras (Ammonitina) from the Jurassic of Skye, Scotland

Successive populations of Graphoceras from the concavum Zone (Aalenian, Middle Jurassic) at Bearreraig (Isle of Skye, N.W. Scotland) contain an unusually high proportion (8-1%) of pathologically deformed specimens, in which the whorls grew over to one side after initial normal growth. Size-frequency distributions and proportions of dimorphs are similar among deformed and normal ammonites, and are consistent with random affliction of members of the populations. The most likely cause of the deformity is disease or parasitic infestation.