Nautiloid -Eutrephoceras geelongensis (Foord)
Middle Miocene
Muddy Creek Formation
Muddy Creek, Hamilton, Victoria
Australia.

Enormous 230mm (9 inch) nautiloid. Extremely rare.

Eutrephoceras geelongensis (Foord) is a rare nautiloid from the Cretaceous of Australia, known for its smooth, rounded shell and elegant coiling. As a distant relative of modern nautiluses, this species once cruised ancient seas using jet propulsion and a keen sense of buoyancy. Its fossils are uncommon and highly sought after, offering a rare glimpse into the diversity of ancient cephalopods in southern hemisphere marine ecosystems.