Large ammonite Pachydiscus sp. from Madagascar (Menabe region), Upper Cretaceous, Campanian (ca. 83 million years ago), with painted wooden base and display stand, diam. 60 cm

The largest ammonites have been found in the Pachydiscidae family. It could reach up to 2.50 metres in diameter. They are the most advanced invertebrates, perfectly adapted to different biotopes.