The Threadfin Butterflyfish, Chaetodon auriga, 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 butterflyfish

Butterflyfish

The butterflyfish are a group of conspicuous tropical marine fish of the family Chaetodontidae; the bannerfish and coralfish are also included in this group. Found mostly on the reefs of the Atlantic, Indian and Pacific Oceans, there are approximately 120 species in 10 genera...

 (family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Chaetodontidae). It is found in the Indo-Pacific

Indo-Pacific

The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...

 region from the Red Sea

Red Sea

The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...

 and eastern Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

 (south to Mossel Bay

Mossel Bay

Mossel Bay is a harbour town of about 130,000 people on the Southern Cape of South Africa. It is an important tourism and farming region of the Western Cape Province...

, South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

) to the Hawaiian

Hawaiian Islands

The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...

, Marquesan

Marquesas Islands

The Marquesas Islands enana and Te Fenua `Enata , both meaning "The Land of Men") are a group of volcanic islands in French Polynesia, an overseas collectivity of France in the southern Pacific Ocean. The Marquesas are located at 9° 00S, 139° 30W...

, and Ducie

Ducie Island

Ducie Island is an uninhabited atoll in the Pitcairn Islands. It lies east of Pitcairn and has a total area of , which includes the lagoon. It is long, measured northeast to southwest, and about wide. The island is composed of four islets: Acadia, Pandora, Westward and Edwards.Despite its...

 islands, north to southern 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...

, south to Lord Howe Island

Lord Howe Island

Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...

 and Rapa Iti

Rapa Iti

Rapa or Rapa Iti as it is sometimes called in more recent years , is the largest and only inhabited island of the Bass Islands in French Polynesia. An older name for the island is Oparo Its area is 40 km2 with a population of almost 500 and a max elevation of 650 m...

, at depths of between 1 and 35 m.

Length is up to 23 cm (9 in). Chaetodon auriga has a neck patch of ascending and a belly patch of descending oblique dark lines. As the name Chaetodon auriga originally refers to the Red Sea population, the spotted population is sometimes separated as subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 Chaetodon auriga setifer.

It belongs to the large subgenus

Subgenus

In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...

 Rabdophorus which might warrant recognition as a distinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

. In this group, it almost certainly is a rather close relative of the Vagabond Butterflyfish

Vagabond butterflyfish

The Vagabond Butterflyfish, Chaetodon vagabundus, is a species of butterflyfish . It is found from the Red Sea and off East Africa as far east as the Tuamotu Islands, north to southern Japan and south to the Austral Islands....

 (C. vagabundus) and the Indian Vagabond Butterflyfish

Indian vagabond butterflyfish

The Indian Vagabond Butterflyfish, Chaetodon decussatus, is a species of butterflyfish . It is found in the Indo-West Pacific, from the Maldives via India, Sri Lanka and the Andaman Sea to the westernmost portion of the Indonesian archipelago.Growing to a maximum of 20 cm long, it is found on rich...

 (C. decussatus). The Threadfin Butterflyfish might be closer to the latter; as C. vagabundus has yielded abnormal DNA sequence

DNA sequence

The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...

data this is hard to say however. The C. auriga species group shares the characteristic pattern of two areas of ascending and descending oblique lines; species differ conspicuously in hindpart coloration.