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| Prognathodes geminus
Copus, Pyle, Greene & Randall, 2019
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Abstract
A new species of the butterflyfish genus Prognathodes (Chaetodontidae) is described from two specimens collected at a depth of 116 m off Ngemelis Island, Palau. Prognathodes geminus sp. n. is similar to P. basabei Pyle & Kosaki, 2016 from the Hawaiian archipelago, and P. guezei (Maugé & Bauchot, 1976) from the western Indian Ocean, but differs from these species in the number of soft dorsal-fin rays, size of head, body width, and body depth. There are also subtle differences in life color, and substantial differences in the mtDNA cytochrome oxidase I sequence (d ≈ 0.08). Although genetic comparisons with P. guezei are unavailable, it is expected that the genetic divergence between P. guezei and P. geminus will be even greater than that between P. geminus and P. basabei. It is named for the strikingly similar color pattern it shares with P. basabei.
Keywords: Closed-circuit rebreather, Mesophotic Coral Ecosystem, Micronesia, systematic ichthyology
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| Figure 2. Paratype of Prognathodes geminus (USNM 440390), collected at a depth of 116 m at Palau. Photograph by RL Pyle. |
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| Figure 1. Holotype of Prognathodes geminus (BPBM 40857), collected at a depth of 116 m at Palau. Photograph by RL Pyle. |
Prognathodes geminus sp. n.
Diagnosis: A species of Prognathodes (sensu Smith et al. 2003) distinguished by the following combination of characters: dorsal-fin soft rays 17–19; anal-fin soft rays 15; head 2.48–2.49 in SL; body depth 1.71–1.76 in SL; pelvic-fin spine length 4.18–4.46 in SL; body color white with three broad dark brown bands, the first intersecting the eye.
Distribution: Prognathodes geminus is positively known only from Palau. However, individuals of what appear to be this species were collected by aquarium-fish collector Tim Bennett in the Coral Sea at a depth of 140 m (Fenton Walsh, pers. comm.), and video taken from a depth of about 120 m in New Caledonia (and reviewed by co-author Pyle) show what appears to be a similar fish. A similar species was recently described from the Hawaiian Islands (P. basabei), but numerous deep dives by the authors and others in regions between Palau and the Hawaiian Islands have not yielded any observations of this species, nor any other members of the genus Prognathodes.
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| Figure 3. Holotype of Prognathodes geminus in its natural habitat at a depth of 116 m off Ngemelis, Palau. Photograph by JL Earle. |
Habitat: Type specimens and other individuals observed from submersible by Patrick L Colin (pers. comm.) in Palau were seen in association with limestone outcroppings on steep slopes at depths of 110–150 m. The type specimens were collected in an area with broken limestone rubble (Figure 3).
Etymology: We name this species geminus, Latin adjective for “twin”, in reference to its similarity in color to P. basabei from the Hawaiian Islands.
Joshua M. Copus, Richard L. Pyle, Brian D. Greene and John E. Randall. 2019. Prognathodes geminus, A New Species of Butterflyfish (Teleostei, Chaetodontidae) from Palau. ZooKeys. 835: 125-137. DOI: 10.3897/zookeys.835.32562
