Tahiti, French Polynesia.

CAS 247193, field code: HTP906, GenBank MN922331. 29.5 mm SL, Tahiti, French Polynesia, 17°29'27"S, 149°28'01"W, depth of collection 105 m, collected with hand nets by B Shepherd, HT Pinheiro, TAY Phelps, MV Bell, and LA Rocha, 03 March 2019.

USNM 445722, field code: HTP942, GenBank MN922330. 32.3 mm SL, Maloelap Atoll, Republic of the Marshall Islands, 8°37'42"N, 170°59'58"E, depth of collection 120 m, collected with hand nets by HT Pinheiro, TAY Phelps, MV Bell, and LA Rocha, 13 August 2019.

Plectranthias polygonius sp. nov. can be distinguished from all of its congeners by live coloration, in particular the two rows of orange rhomboid-shaped polygons on the lateral part of the body and an elongated yellow and white third dorsal spine (Fig. 1A, D), and by the following combination of characters: dorsal-fin rays X, 16; pectoral-fin rays 14, all unbranched; vertebrae 10+16; continuous lateral line with 27–30 tubed scales; circumpeduncular scales 10 or 11; absence of antrorse spines on the preopercle.

Figure 1. 

Plectranthias polygonius sp. nov. holotype A shortly after death B preserved C radiograph, and paratype D shortly after death E preserved F radiograph. Photographs by LA Rocha (A), A Gaisiner (B, E), J Fong (C, F), and T Sinclair-Taylor (D).

Proportional measurements for the type specimens are presented in Table 1. Dorsal rays X, 16, the last soft ray branched to base and counted as one; first dorsal spine short, 18.0 in SL (15.8); third dorsal spine longest, 1.7 in HL (1.6) with flag-like extension; dorsal-fin base length 2.1 in SL (1.9); anal-fin rays III, 7, last soft ray branched to base and counted as one; anal-fin base length 6.3 in SL (6.5); second anal spine longest and stoutest at 1.6 in HL; anal-fin origin at vertical beneath fourth dorsal-fin ray; pectoral-fin rays 14, all unbranched, length 3.8 in SL (3.4); pelvic fin I, 5; pelvic-fin length 4.6 in SL (4.2); pelvic-spine length 2.0 in HL; procurrent caudal-fin rays 7+6 (6+5); principal caudal-fin rays 9+8.

Body moderately elongate, laterally compressed; depth of body 3.4 in SL (3.2); width of body 2.7 in depth (2.3); head length 3.2 in SL (3.1); snout length 3.4 in HL (3.6); bony interorbital width 1.6 in snout length (1.3); orbit diameter 2.8 in HL; post-orbital head length 4.8 in SL (4.7); least depth of caudal-peduncle 2.5 in HL; caudal peduncle length 3.6 in HL (4.0).

Scales ctenoid; lateral line complete and broadly arched over pectoral fin following body contour; 30 (27) tubed scales; scales above lateral line to origin of dorsal fin 2; scales above lateral line to base of middle dorsal spine 2; scales below lateral line to origin of anal fin 9 (10); diagonal rows of scales on cheek 5; scales on top of head extending anteriorly to vertical from anterior margin of pupil; no scales on chin, maxilla, or snout; circumpeduncular scales 10 (11); gill rakers 5+13 (6+13); vertebrae 10+16; supraneurals 3; anterior supraneural-dorsal ray-pterygiophore-neural spine interdigitation pattern: 0/0+0/2/1+1/1.

Mouth large and terminal, slightly upturned; lower jaw protrudes slightly; maxilla expanded posteriorly, extending to below the posterior edge of eye; dorsal profile of head almost straight; upper jaw with one fixed, stout canine on either side of symphysis; upper canines flanked internally by villiform band with four or five rows of depressible, smaller, sharp-tipped teeth; inner rows become progressively longer, innermost row with largest teeth; lower jaw has pair of fixed, short stout canines on either side of symphysis followed by smaller, depressible, sharp-tipped conical teeth in a villiform band of 3–5 rows; lower teeth become progressively longer on inner rows; vomer roughly V-shaped band of two rows of similarly sized, sharp-tipped, conical teeth; palatines with one row of small, sharp-tipped conical teeth; tongue small, slender, pointed, and without teeth.

Opercle with three spines, the middle spine the longest; preopercle with 14 (17) small spines (serrae) along posterior margin; antrorse spines lacking on ventral margin; interopercle with no spines; subopercle smooth, with no spines; anterior nostrils positioned halfway between snout and eye, each with a small rounded flap rising from anterior rim; posterior nostrils an elliptical opening at anterior border of orbit.

Body : overall white with two rows of bright orange rhomboid-shaped polygons, four to six in each row, arranged in an irregular grid along lateral midline of body; uppermost row of orange polygons proceeds from behind eye to dorsal third of caudal peduncle; lower row starts just dorsal to origin of pectoral fin and continues to ventral half of caudal peduncle; throat and belly white. Head: dorsal third of head orange and bottom two thirds pinkish white with two yellow stripes, both originating from the tip of the upper lip. The first extending horizontally across orbit, bifurcating past posterior edge of pupil to approximately edge of opercle. The second from tip of upper lip, tracing obliquely along maxilla and extending to ventral edge of preopercle. Preopercle region with a yellow triangular patch, from lower mid-orbit expanding in width to edge of preopercle with bifurcations to horizontal edge of operculum and pelvic fin bases respectively; orbit mostly orange-red; iris outlined in silver-grey to black with horizontal yellow stripe through middle of anterior portion; posterior portion of iris with two yellow stripes arising from a bifurcation of the anterior yellow stripe; pupil black. Fins: first three membranes of spinous portion of dorsal fin mostly orange with yellow highlights; third spine with yellow and white membrane; remaining membranes of spinous portion mostly yellow, with hyaline tips; yellow coloration continues on lower third of soft portion of dorsal fin, with upper two-thirds mostly hyaline; some yellow and pale orange on tips of soft dorsal and membranes of last four to five rays; caudal fin hyaline with white and orange rays; anal fin mostly yellow, with white margin; pelvic fins mostly white distally, with yellow rays proximally; pectoral fins hyaline. Living specimen photographed in the Marshall Islands exhibits more yellow coloration on head, within rhomboid-shaped polygons on lateral midline, and on first three membranes of spinous dorsal fin (Fig. 2A).

Figure 2. 

Plectranthias polygonius sp. nov. at Erikub Atoll, Republic of the Marshall Islands, at a depth of 120 m (A), aquarium photos of P. inermis (B), and P. altipinnatus (C). Photographs by LA Rocha (A) and YK Tea (B, C).

Light tan overall, with no visible markings.

Plectranthias polygonius sp. nov. is named for the orange rhomboid-shaped polygons arranged in parallel rows along the lateral midline that distinguish it from all other known species within the genus. To be treated as a noun in apposition.

Plectranthias polygonius sp. nov. appears to be the same species as an undescribed Plectranthias species that was photographed off Rangiroa, French Polynesia, at a depth of 65 m (Williams et al. 2013). However, some superficial differences exist between our specimen and the one in Williams et al. (2013), including the thickness of the white lines on the upper body and the color of the iris. These may be due to individual variability. The two specimens described in this paper were collected in highly complex reefs predominantly covered by coralline algae and sponges in Tahiti (Fig. 3A) and crevices of steep reef walls in the Marshall Islands (Fig. 3B), indicating that this species probably has a wider Pacific distribution. All known individuals have been observed or collected at mesophotic depths, suggesting that Plectranthias polygonius sp. nov., as with most of its congeners, does not inhabit shallow coral reef habitats.

Figure 3. 

Habitat of Plectranthias polygonius sp. nov. and Plectranthias hinano sp. nov. in A Tahiti, French Polynesia, depth of approximately 100 m, and B Erikub Atoll, Republic of the Marshall Islands, depth of approximately 120 m. Photographs by LA Rocha.

The general body shape, color, and prolongation of the third dorsal-fin spine in Plectranthias polygonius sp. nov. resemble P. inermis and P. altipinnatus (Fig. 2B, C); however, the barcode fragment of the COI gene of P. polygonius sp. nov. is not close to any published barcode sequence of Plectranthias, with approximately 15% uncorrected pairwise genetic distance from several species in the genus. Morphologically, it can easily be distinguished from P. inermis by having ten circumpeduncular scales (vs. 14 or 15 in P. inermis); canine teeth on the lower jaw (lacking in P. inermis); and 14–17 spines on the posterior edge of the preopercle (spines lacking in P. inermis; feebly serrated in P. altipinnatus). The new species differs from P. altipinnatus by having X, 16 dorsal-fin rays (X, 18 in P. altipinnatus), a shallower body (3.2–3.4 in SL vs. 2.8 in P. altipinnatus), smaller head (3.1–3.2 in SL vs. 2.2 in P. altipinnatus), and a larger eye (2.8 in HL vs. 4.75 in P. altipinnatus).

Tahiti, French Polynesia

CAS 247195, field code: HTP909, GenBank MN922329. 49.6 mm SL, Tahiti, French Polynesia, 17°29'27"S, 149°28'01"W, depth of collection 98 m, collected with hand nets by B Shepherd, HT Pinheiro, TAY Phelps, MV Bell, and LA Rocha, 03 March 2019 (Fig. 4).

Figure 4. 

Plectranthias hinano sp. nov. holotype A shortly after death B preserved specimen C radiograph. Photographs by LA Rocha (A), A Gaisiner (B), and J Fong (C).

USNM 445723, field code: TAH007, GenBank MN922328. 28.0 mm SL, Tahiti, French Polynesia, 17°36'59"S, 149°37'13"W, depth of collection 90 m, collected with hand nets by B Shepherd, HT Pinheiro, TAY Phelps, MV Bell, and LA Rocha, 28 February 2019.

Plectranthias hinano sp. nov. can be distinguished from all of its congeners by the following combination of characters: dorsal-fin rays X, 15, the last branched to base and counted as one; pectoral fin rays 11 or 12; vertebrae 10+16; lateral line complete with 29–30 tubed scales; gill rakers 7–8+12–13; ventral margin of preopercle with three antrorse spines; snout moderately long, 3.0–3.2 in HL, 12.3–14.2% SL, overall red coloration with two indistinct black spots along the base of dorsal fin, translucent yellow dorsal and anal-fin membranes.

Proportional measurements for the type specimens are presented in Table 1. Dorsal-fin rays X, 15; last soft ray branched to base and counted as one; first dorsal spine very short, 17.6 in SL (9.4); fourth dorsal spine longest, 5.5 in SL (third dorsal spine longest, 6.4 in SL); dorsal-fin base length 2.1 in SL (1.9); anal-fin rays III, 7; last soft ray branched to base and counted as one; anal-fin base 6.2 in SL (5.3); second anal spine longest and stoutest at 2.0 in HL (2.1); anal-fin origin at vertical beneath fourth dorsal-fin ray; pectoral-fin rays 11 (12), all unbranched, length 2.8 in SL (2.6); pelvic fin I, 5; pelvic-fin length 4.6 in SL (4.0); pelvic-spine length 2.4 in HL (2.3); caudal-fin procurrent rays 6+5; caudal-fin principal rays 9+8.

Body moderately elongate, laterally compressed; depth of body 2.9 in SL (3.0); width of body 2.1 in depth (2.4); head length 2.4 in SL (2.5); snout length 3.0 in HL (3.2); bony interorbital width 3.5 in snout length (2.3); orbit diameter 3.7 in HL (3.5); post-orbital head length 5.4 in SL (5.6); least depth of caudal-peduncle 3.7 in HL (3.4); caudal-peduncle length 4.0 in SL (4.1).

Scales ctenoid; lateral line complete and broadly arched over pectoral fin following body contour; 29 (30) tubed scales; scales above lateral line to origin of dorsal fin 3; scales above lateral line to base of middle dorsal spine 2; scales below lateral line to origin of anal fin 12; diagonal rows of scales on cheek 4; scales on top of head extending anteriorly to vertical from center of eye; area on top of head between eyes with scales; no scales on chin, maxilla, or snout; circumpeduncular scales 12; gill rakers 8+13 (7+12); vertebrae 10+16; supraneurals 3; anterior supraneural-dorsal ray-pterygiophore-neural spine interdigitation pattern: 0/0+0/2/1+1/1.

Mouth large and terminal, slightly upturned; lower jaw protrudes slightly; maxilla expanded posteriorly, extending to below the posterior edge of pupil; upper jaw with one fixed, stout canine on either side of symphysis; upper canines flanked internally by villiform band with 7–9 irregular rows of depressible, smaller, sharp-tipped teeth; inner rows become progressively longer, innermost row with largest teeth; lower jaw has one large, fixed canine on either side of lower jaw, roughly at midpoint, followed by smaller, depressible, sharp-tipped conical teeth in a villiform band of 4–6 irregular rows, innermost teeth same size as outer rows; vomer roughly V-shaped band of two rows of similarly-sized, sharp-tipped, conical teeth; palatines with one row of small, sharp-tipped conical teeth anteriorly, two rows posteriorly; tongue small, slender, pointed, and without teeth.

Opercle with three flat spines, the middle spine the longest; preopercle with 22 (12) small spines (serrae) along posterior margin; ventral (inferior) margin of preopercle with three antrorse spines; interopercle with no spines; subopercle smooth, with one spine on inferior margin; anterior nostrils positioned closer to eye than to snout, each with a small rounded flap rising from anterior rim; posterior nostrils an elliptical opening at anterior border of orbit.

Body : overall light red in color; chest and belly mostly light red to pink; dorsal portion of body darker red with yellow along scale margins and lateral line; series of 8–12 pink to white incomplete bars on the body, originating just behind orbit and continuing to base of caudal fin; bars are approximately 20 degrees off of vertical anteriorly, becoming near vertical as they approach base of caudal fin; black spot, almost twice the diameter of orbit, at base of spinous dorsal-fin spines 7–10 and soft rays 1–5, continuing slightly more than halfway up membrane of spinous dorsal; black spot is interrupted by the near-vertical white bar originating below soft rays 1 or 2; smaller second black spot, slightly smaller than orbit, located at base of soft dorsal rays 11–15. Head: snout, throat, anterior portion of lower lip, maxilla, and operculum mostly light pink; yellow stripe originating at snout, proceeding across maxilla, below orbit to preopercle; lattice-like network of indistinct yellow stripes radiating outward from pupil across iris, between eyes, across top of head, from ventral margin of orbit to origin of lateral line and lower margin of operculum; iris mostly pink with yellow splotches radiating outward from pupil; pupil black and teardrop-shaped, pointed anteriorly. Fins: spinous portion of dorsal fin predominantly translucent yellow, with upper half of black spot on membrane between spines 7–10; lower third of soft dorsal fin mostly translucent yellow, upper two-thirds hyaline; caudal-fin membranes mostly hyaline with some regions a faint transparent yellow, fin rays white with red margins; pelvic fins hyaline with faint yellow on rays; anal fin mostly translucent yellow with hyaline margins; pectoral fins hyaline with rays outlined in pink; base of pectoral fins yellow. Freshly dead specimens exhibit similar coloration, with slightly more yellow on head, body, and fins (Fig. 4A).

Light tan overall, with dark brown stippling in vertical bands along lateral sides of body, darkest brown along base of dorsal fin at location of black spots.

Plectranthias hinano sp. nov. is named after Teurumereariki Hinano Teavai Murphy, former associate director of the University of California Berkeley Gump Research Station and president of the cultural association Te Pu Atitia, in honor of the significant contributions she has made supporting Polynesian biocultural heritage and field research in Moorea, French Polynesia. The name is a noun in the genitive case.

The two specimens described in this paper, plus an individual that was retained for public aquarium exhibition, were collected respectively in Tahiti and Moorea, French Polynesia. A similar species was photographed at 120 m depth in Erikub Atoll, Republic of Marshall Islands, however specimens were not retained (Fig. 5B). The Marshall Islands specimens lack the black markings along the dorsal-fin base, and thus more closely resemble Plectranthias bennetti (Fig. 5C), indicating that the latter may have a wider Pacific distribution and not just be restricted to the Coral Sea. All known individuals of P. hinano sp. nov. have been observed or collected in highly complex habitats on walls and ledges within MCEs (Fig. 3), suggesting that the species does not inhabit shallow coral reefs.

Figure 5. 

Living specimens of A Plectranthias hinano sp. nov. at Steinhart Aquarium, California Academy of Sciences B Plectranthias cf. bennetti photographed at a depth of 120 m at Maloelap Atoll, Republic of the Marshall Islands, and C Plectranthias bennetti photographed in an aquarium. Photographs by T Wong (A), LA Rocha (B), and YK Tea (C).

The most similar barcode fragment of the mtDNA COI gene to Plectranthias hinano sp. nov. is P. bennetti from the Coral Sea (5.5% uncorrected pairwise genetic distance). Morphologically, it can be distinguished from P. bennetti by having a longer snout (3.0–3.2 in HL vs. 4.4 in P. bennetti), a larger orbit (3.5–3.7 in HL vs. 4.1 in P. bennetti), in the number of circumpeduncular scales (12 vs. 14 in P. bennetti), the number of gill rakers (7–8 + 12–13, vs. 5+13 in P. bennetti), and in coloration (by having two indistinct black spots along the base of the dorsal fin, and yellow dorsal and anal fin membranes).