Dr. Richard Pyle and E.H. Chave first reported the presence of a species the butterflyfish genus Prognathodes in the Hawaiian Islands at depths of 106–187 meters, based on video and observations from research submersibles operated by the Hawaii Undersea Research Laboratory (HURL). They noted its similarity to P. guezei, a species then known only from the two type specimens collected at a depth of 80 meters off Réunion Island in the western Indian Ocean.

While conducting an exploratory dive using a mixed-gas closed-circuit rebreather off the south shore of O‘ahu (Main Hawaiian Islands) on May 17, 1998, Dr. Pyle observed (but was unable to collect) a group of three Prognathodes near an undercut limestone ledge at a depth of 114 meters. Two weeks later, with the assistance of Peter K. Basabe, Dr. Pyle collected the first specimen of this species at a depth of 120 meters near Kealakekua Bay on the Kona coast of the island of Hawai‘i. The following day he collected several more individuals at a depth of 115 meters near the O‘ahu site. All of the collected individuals were brought to the surface alive and maintained in captivity. Unfortunately, when they eventually died, only one was preserved, and it was too badly deteriorated to serve as a type specimen.

In September of 2015, Dr. Pyle and Dr. Randall Kosaki were able to collect three more specimens at the same site off Pearl and Hermes Atoll where the three specimens had been collected in 2009, and obtain additional tissue samples for genetic analyses. Based on an examination of both morphological and genetic characters of the six Hawaiian specimens, as well as comparisons with the two specimens from Palau and Prognathodes guezei, they were able to confirm that the Hawaiian population represents a new species, distinct from both P. guezei and the undescribed Palauan species. They described the Hawaiian population as the new species, Prognathodes basabei. The three butterflyfish pictured above are the same three collected in September 2015, and they currently live in Bishop Museum’s Science Adventure Center! Be sure to check out this unique specimen on your next visit!

References: https://zookeys.pensoft.net/articles.php?id=10200