Allonautilus scrobiculatus

Allonautilus scrobiculatus, also known as the crusty nautilus or fuzzy nautilus, is a special kind of sea creature called a nautilus. It lives deep in the ocean around New Guinea, especially near New Britain and Milne Bay, as well as the Solomon Islands. This nautilus has a unique shell with a large open space in the middle, called an umbilicus, which makes up about 20% of the shell’s width.

Scientists used to think A. scrobiculatus belonged to the same group as other nautiluses, but they later realized it was different enough to have its own group, called a genus. Its shell has special features, like creases and a fuzzy layer that covers most of it. This nautilus also has different gills and reproduction systems compared to other nautiluses.

The shell of A. scrobiculatus is usually about 18 cm wide, but the biggest one ever found was 21.5 cm across. Many people thought this nautilus had disappeared forever after 1986, but in July 2015, scientists were excited to find it again, proving that it still exists in the ocean today.

Taxonomy

The genus Allonautilus has only two species and is closely related to the Nautilus genus, which has 11 species — five of them are widely accepted as distinct. Not much is known about Allonautilus because it has not been studied much. However, the Nautilus genus has been known to scientists since the time of the Renaissance. Nautiluses do not change much over time and are distant relatives of squids and octopuses.

Description

The Allonautilus scrobiculatus, also called the crusty nautilus or fuzzy nautilus, looks different from other nautiluses. It has a thick, hairy shell covered in slime and white, oddly shaped bumps that stick out from its hood.

This nautilus has a special shell shape with many grooves, unlike its close relative, the Allonautilus perforatus. Though they look similar, the grooves make A. scrobiculatus easy to tell apart. Its gills are smaller and simpler than those of regular nautiluses.

One unusual feature is its "shell skin," called the periostracum, which looks like slimy hair on freshly caught samples.

Distribution and habitat

Allonautilus scrobiculatus lives in the waters near Papua New Guinea and the Solomon Islands. It is usually found at depths between 500 and 1,300 feet below the surface. This nautilus prefers cooler, deeper waters and cannot survive in very shallow or extremely deep areas.