Proportional measurements expressed as a percentage of standard length (SL). Data in parentheses apply to paratypes, when different from the holotype (see also Table 1).

Dorsal soft rays 29; anal rays 25; pectoral rays 13 (rarely 14); body scale rows 34 (33-35); head scale rows 18 (17-18); vertebrae 18, gill rakers 36 (holotype only).

Greatest depth of body 49 (45-50), depth at origin of anal fin 41 (42-43), width of body 29 (19-20), head length 32 (31-33), snout length 21 (20-21), snout to origin of first dorsal fin 33 (32-35), snout to origin of anal fin 69 (67-69), base of second dorsal fin 36 (35-37), base of anal fin 30 (30-32).

Eye diameter 6.5 (7.2-8.8), interorbital width 12 (12-13), length of gill opening 10 (9-10), depth of caudal peduncle 8.4 (8.4-9.0), length of first dorsal spine 14 (13-17), length of longest dorsal soft ray 19 (19-22), length of longest anal ray 18 (16-19), interdorsal space 25 (23-25), length of caudal fin 26 (21-26), caudal concavity 4.5 (2.1-5.8), length of pectoral fin 11 (12-14).

Dorsal and ventral profiles of head strongly convex; three longitudinal slightly diagonal darkly pigmented grooves on head following border of scale rows, running from behind and below corner of mouth, converging slightly as they pass posteriorly, and nearly reaching gill opening and upper pectoral base; a groove running anteriorly and diagonally downward from front of eye, extending approximately half the distance to tip of snout; deep medial groove behind first dorsal fin extending approximately half distance from last spine to origin second dorsal; pelvic flap not developed, pelvic terminus barely movable, small, slightly over one half orbit diameter.

Color in life as in Figs 1, 2; pearly gray, some paratypes with light brownish cast, slightly whiter ventrally on body, faint light blueish cast to head; irregular honey-brown spots sub-dorsally on body in several irregular rows commencing anteriorly at the origin of the first dorsal spine, becoming an irregular row prior to the origin of the second dorsal and ending posteriorly with a few scattered spots on the caudal peduncle; honey-brown diffuse bar below the anterior sub-dorsal spots and immediately posterior to gill opening, running from mid-orbit to slightly below mid-anterior pectoral base, opercular membrane darkly pigmented; three cheek grooves pigmented pale blue, dark on some paratypes, a weak groove above the three pigmented grooves faintly pigmented on some paratypes, groove extending anteriorly and diagonally downward from eye with faint blue pigment on some specimens; dark brown line below lower lip, thickening and extending diffusely beyond corner of mouth; first dorsal fin light tan brown becoming dark distally, first dorsal fin membrane basally tan, dark brown distally, second dorsal and anal fins with light brown rays, light blueish membranes; caudal fin with reddish upper and lower margins, a broad reddish crescent posteriorly in fin not extending to upper and lower margins, a light blueish area forming a diffuse crescent in the center of the fin; pectoral fin not pigmented. When viewed alive underwater the overall color appears light blue-gray.

Figure 1.  

Holotype of Xanthichthys greenei (BPBM 40262), from Kiritimati (Christmas Island), Line Islands. Photo: R.L. Pyle.

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Figure 2.

Paratypes of Xanthichthys greenei, sp.n., showing variation in cheek-groove pigmentation and dorsal spot patterns. Photos by R. L. Pyle and B. D. Greene.

Color in alcohol tan, paler ventrally; pale brown spots dorsally from origin of dorsal fin to caudal peduncle, more spots anteriorly; grooves in cheek brown; opercular membrane brown, faint brown bar posterior to gill opening from mid-orbit to mid pectoral base; brown line below lower lip extending diffusely beyond corner of mouth; anterior nostril in a small white spot; first dorsal spine light brown, darker distally on some specimens, membrane of first dorsal fin brown, darker posteriorly; second dorsal and anal fins pale with light brown rays; caudal fin pale yellow; pectoral fins translucent.

Dorsal rays III, 29; anal rays 25; pectoral rays 13–14 (usually 13); body scale rows 33-35; head scale rows 17–18; gill rakers 36; body depth 2–2.22 in SL; color in life pearly gray with honey-brown spots sub-dorsally on body in several irregular rows between the first dorsal spine and the caudal peduncle; opercular membrane darkly pigmented with three cheek grooves pigmented pale blue; first dorsal fin light tan brown becoming dark distally, first dorsal fin membrane basally tan, dark brown distally, second dorsal and anal fins with light brown rays, light blueish membranes; caudal fin with reddish upper and lower margins, a broad reddish crescent posteriorly in fin not extending to upper and lower margins.

Named for Brian D. Greene, a member of the deep diving team that discovered species, in recognition of his efforts to collect the type specimens.

Currently known only from Kiritimati (Christmas Island) in the Line Islands. Further exploration of mesophotic coral ecosystems in the tropical Pacific may extend the known range of this species, although it was not observed during exploratory dives within the mesophotic depth range in the Hawaiian Islands, Johnston Atoll, Caroline Islands, Cook Islands, French Polynesia, or elsewhere in the Pacific.

Relatively abundant within its depth range and habitat (coral rubble and holes adjacent to deeper drop-offs, below a thermocline) at several localities on the west and north coasts of Kiritimati (Christmas Island). Always observed near the reef substratum, where it would retreat to shelter when approached.