Chaetodon falcula
[2] Chaetodon falcula is found in the Indian Ocean where it occurs along the East African coast between Kenya and South Africa, Madagascar and the other western and central islands of the Indian Ocean, Sri Lanka, southern India, including the Andaman and Nicobar Islands, and from the waters of western Thailand east as far as Java.[5] Chaetodon falcula was first formally described in 1795 by the German physician and naturalist Marcus Elieser Bloch (1723–1797) with the type locality given as Tharangambadi in India.[6] The specific name falcula is a diminutive of the Latin falx or falcis meaning a "sickle" or a "scythe" and is a reference to the wedge shaped black saddle blotches which Bloch illustrated as sickle-shaped, which they are not in modern photographs.[7] With its sister species, the similar-looking Pacific double-saddle butterflyfish (C. ulietensis),[4] C. falcula belongs to the large subgenus Rabdophorus which might warrant recognition as a distinct genus.The bluish vertical lines are present in all of these, while a white body with yellow behind and black on back and caudal peduncle are only shared among the four less ancient species.