Gandalfus yunohana is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of crab

Crab

True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

.

G. yunohana is found on hydrothermal vent

Hydrothermal vent

A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...

s on the eastern edge of the Philippine Sea Plate south of Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. It lives at shallower depths than other members of the family Bythograeidae

Bythograeidae

Bythograeidae is a small family of crabs which live around hydrothermal vents. The family contains 14 species in 6 genera. Their relationships to other crabs are unclear...

, at 420–1380 m (1,378–4,527.6 ). Because no light penetrates to such depths, the eyes of G. yunohana are immobile and unpigmented.

Males have a carapace

Carapace

A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...

 up to 39 by 24.5 mm (1.5 by 0.964566929133858 ) across, while females are larger, at 41 by 25.8 mm (1.6 by 1 ).

It was originally described as Austinograea yunohana in 2000, but was transferred in 2007 by Colin McLay to his new genus, Gandalfus, named after the character Gandalf

Gandalf

Gandalf is a character in J. R. R. Tolkien's novels The Hobbit and The Lord of the Rings. In these stories, Gandalf appears as a wizard, member and later the head of the order known as the Istari, as well as leader of the Fellowship of the Ring and the army of the West...

 from The Lord of the Rings

The Lord of the Rings

The Lord of the Rings is a high fantasy epic written by English philologist and University of Oxford professor J. R. R. Tolkien. The story began as a sequel to Tolkien's earlier, less complex children's fantasy novel The Hobbit , but eventually developed into a much larger work. It was written in...

.