The Millet Butterflyfish, Chaetodon miliaris, 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).

In its 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...

 Exornator it probably belongs to a group that also includes the African Butterflyfish

African butterflyfish

African butterflyfish may refer to:* Freshwater butterflyfish, Pantodon bulchhozi, a freshwater bonytongue fish* Chaetodon dolosus, a saltwater butterflyfish...

 (C. dolosus), the Crochet Butterflyfish (C. guentheri) and the Reef Butterflyfish

Reef butterflyfish

The reef butterflyfish, Chaetodon sedentarius, is a butterflyfish of the family Chaetodontidae found in the western Atlantic Ocean from Brasil to North Carolina including Bermuda and the Gulf of Mexico....

 (C. sedentarius). The Crochet Butterflyfish might be the closest living relative of C. miliaris. If the 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...

 Chaetodon

Chaetodon

Chaetodon is a tropical fish genus in the family Chaetodontidae. Like their relatives, they are known as "butterflyfish". This genus is by far the largest among the Chaetodontidae, with about 90 living species included here, though most might warrant recognition as distinct genera.Several subgenera...

is split up, Exornator might become a subgenus of Lepidochaetodon.

This fish is endemic to the Hawaiian islands

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...

.