Description

Diplomoceras is a genus of ammonites classified within the Diplomoceratidae family. Fossils of species belonging to this genus have been discovered in Late Cretaceous sediments, specifically from the Campanian to Maastrichtian periods.

One of the notable species within this genus, D. maximum, exhibited an intriguing shell structure. Its coiled shell had a length of about 1.5 meters (4.9 feet), while the uncoiled shell could reach anywhere from 3 meters (9.8 feet) to over 4 meters (13 feet), with a body chamber measuring around 2 meters (6.6 feet). In some instances, partial specimens might have had a shell length of around 1.7 meters (5.6 feet). Notably, studies of Diplomoceras suggest that these ammonites might have had lifespans exceeding 200 years.

Shell like a paperclip

Diplomoceras stood out due to its unconventional shell shape. Instead of the tightly wound spiral typical of most ammonites, Diplomoceras' shells began straight, forming a U-bend, and then curving in the opposite direction to create another U-bend. This pattern repeated, with the shell extending beyond its initial extent before reaching the head opening.

The precise reason for this unique shell structure remains uncertain. It's possible that this feature helped Diplomoceras species distinguish themselves from other ammonite species inhabiting the Late Cretaceous oceans. A more streamlined shell might have facilitated faster swimming, reminiscent of earlier orthocones, and increased their chances of evading predators like large shell-crushing mosasaurs such as Proganthodon and Globidens, which were prevalent in Late Cretaceous seas. This could also explain why Diplomoceras only appeared during the Campanian period of the Late Cretaceous.