Sepia plana is a species of cuttlefish

Cuttlefish

Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....

 native to the coast of Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, specifically the North West Shelf

North West Shelf

The North West Shelf of Western Australia is an extensive oil and gas region off the North West Australia coast in the Pilbara region.It has a considerable number of oil and gas wells, pipelines, production areas and support facilities.- Location :...

 (12°04′S 122°59′E to 17°55.5′S 118°16.0′E). However, cuttlebone

Cuttlebone

Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure found in all members of the family Sepiidae, commonly known as cuttlefish....

s of this species have also been found off eastern Australia, suggesting that it may have a wider distribution. S. plana lives at depths of between 396 and 505 m.

S. plana exhibits sexual dimorphism

Sexual dimorphism

Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

, as females grow considerably larger than males. They reach a mantle

Mantle (mollusc)

The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...

 length of 151 mm and 99 mm, respectively.

The type specimen was collected in the North West Shelf, western Australia (14°15′S 121°59′E). It is deposited at the Museum of Victoria in Melbourne

Melbourne

Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...

.