Holotype. USNM 446947, 73.9 mm SL, CURASUB19-01, tissue no. CUR19001, 117 m, Substation Curaçao Downline, Bapor Kibra, Curaçao, 12.0832, -68.8991, C.C. Baldwin, L. Tornabene, B. Van Bebber, W.B. Ludt, 6 May 2019.

Paratypes. Curaçao: All collected at the type locality off Curaçao: USNM 414901, 33.4 mm SL, CURASUB12-15, tissue no. CUR12142, 123–160 m, A. Schrier, B. Brandt, C.C. Baldwin, A. Driskell, P. Mace, 10 Aug 2012; USNM 414902, 36.1 mm SL, CURASUB12-15, tissue no. CUR12141, 123–160 m, A. Schrier, B. Brandt, C.C. Baldwin, A. Driskell, P. Mace, 10 Aug 2012; USNM 413966, 24.7 mm SL, CURASUB13-03, tissue no. CUR13056, 53–189 m, C.C. Baldwin, A. Schrier, D.R. Robertson, C.I. Castilla, B. Brandt, 7 Feb 2013; USNM 413947, 23.4 mm SL, CURASUB13-02, tissue no. CUR13013, C.C. Baldwin, A. Schrier, D.R. Robertson, C.I. Castilla, B. Brandt, 6 Feb 2013; USNM 430030, 14.9 mm SL, tissue no. CUR13335, Substation Curaçao Crew, 9 July 2013; USNM 406206, 24.1 SL, CURASUB11-03, tissue no. CUR11206, 119–161 m, A. Schrier, M. van der Huls, C.C. Baldwin, D.R. Robertson, J. Oliver, 24 May 2011; CAS 247234, 90.7 mm SL, CURASUB19-02, tissue no. CUR19010, C.C. Baldwin, L. Tornabene, T. Christiaan, S. Yerrace, 7 May 2019; UW 200069, 98.4 mm SL, tissue no. CUR19003, 106 m, C.C. Baldwin, L. Tornabene, B. Van Bebber, W.B. Ludt, 6 May 2019; UW 200070, 97.1 mm SL, CURASUB19-02, tissue no. CUR19009, C.C. Baldwin, L. Tornabene, T. Christiaan, S. Yerrace, 7 May 2019; Sint Eustatius: USNM 442658, 13.9 mm SL, CURASUB17-17, tissue no. EUS17005, South and southeast of R/V Chapman mooring, SW of island, Kay Bay, St. Eustatius, 17.4599, -62.9817, C.C. Baldwin, L. Tornabene, B. Brandt, J. Casey, 15 April 2017. See Suppl. material 1: Table S1 for non-type material examined.

Curaçao, Netherland Antilles.

Dorsal rays XIII, 12–13; anal rays II, 12–13; pored lateral-line scales 15–18 (usually 17; one paratype with ten and no apparent scale loss or damage); gill rakers 7–8+16–18. Proportional measurements expressed as percent standard length, unless otherwise noted as percent head length (HL): head length 30.2–41.0 (mean 35.4); predorsal length 31.1–42.0 (mean 34.9); orbit diameter 11.5–17.4 (mean 14.6), 39.0 (35.4–48.5) % HL; upper jaw length 9.1 (6.0–14.4), 30.0 (22.3–34.8) % HL; snout length 7.8 (6.9–10.3), 26.0 (17.5–32.2) % HL; interorbital width 10.7 (8.6–12.8), 35.4 (21.1–37.4) % HL; body depth 41.6–57.8 (mean 51.8); caudal length 29.7–44.9 (mean 37.20); last dorsal spine 10.2–16.4 (mean 13); longest dorsal ray 21.1–26.5 (mean 23.3); longest anal ray 18.9–28 (mean 24.3); 1^st pelvic soft ray 28.8–43.2 (mean 36.4). See Table 3. Live coloration with thin iridescent blue oblique stripe extending from snout, through eye, ending below origin of spinous dorsal fin, dorsal half of head dark blue to dusky gray, dark coloration continuing in oblique line across dorsal half of body to end of spinous dorsal fin; ventral half of body, soft dorsal fin, paired fins, and caudal fin white; no yellow pigmentation on body or fins.

Body deep, 55.2 (41.6–57.8), laterally compressed, width 19.4 (16.6–21.6), oval in shape; eyes large, 11.8 (11.5–17.4), interorbital width 10.7 (8.6–12.1). Mouth small, upper jaw length 9.1 (6.0–14.4), terminal, and oblique. Head large, 30.2 (30.2–41.0) and rounded with a convex forehead and short snout 7.8 (5.2–10.3), snout length shorter than orbit diameter (snout ~ 1.8 times in orbit). Preopercle mostly smooth with slight serration at ventral angle; opercle possesses one large spine on dorsal posterior side. Suborbital bones mostly joined to cheek, save for second and third, which flex away from cheek with preorbital. Vertebrae 25 plus urostyle (Fig. 6). Gill rakers very long and slender, closely spaced, equal to or greater than the length of gill filaments, with very fine serrations, 7+17 (7–8+16–18). Teeth in both jaws short and conical, arranged in three rows anteriorly, outer row very slightly enlarged, becoming two rows posteriorly.

Dorsal fin XIII, 12 (12–13); longest dorsal ray 23.8 (21.1–28.5); last (13^th) dorsal spine 16.4 (10.3–16.4); spinous dorsal base 48.6 (35.5–50.2); soft dorsal base 18.9 (13.4–18.9); pre-dorsal length 33.2 (31.1–42.0). Anal fin II, 12 (12–13); longest anal-fin ray 23.4 (18.9–28.0); pre-anal length 64.1 (63.2–69.0). Pectoral fin 18 (17–20) and lacking free rays; longest pectoral ray 34.2 (31.1–38.1). Pelvic fin I, 5; with a very long first pelvic ray 40.9 (28.8–43.2); pre-pelvic length 35.2 (35.2–43.6). Caudal fin forked with length 41.0 (29.7–44.9).

Scales large, coarsely ctenoid, covering body and most of head, often densely clustered at base of dorsal and anal fins. Pored lateral-line scales 17 (15–18), total scales in lateral series 28 (26–28); one paratype (USNM 430030, 14.9 mm SL) with only 10 pored lateral-line scales, lateral line terminating below the 10^th dorsal spine in all individuals, without apparent damage or scale loss. Scales above lateral line 4 (3–4). Scales below lateral line 10 (10–11). Circumpeduncular scales 14 (13–4). No obvious pored or pitted scales on caudal peduncle.

Live coloration (Fig. 7): Adults (Fig. 7A–C, F) charcoal gray, sometimes tinged with iridescent blue from head to end of spinous dorsal base, with an abrupt, oblique division between dark dorsal portion and light lower body starting at pectoral-fin base and extending to end of spinous dorsal fin; ventral portion of body, soft dorsal fin, paired fins, and caudal fin bright white with no yellow pigmentation. Head with short, oblique iridescent blue stripe originating on upper lip extending through upper edge of eye extending onto side of nape above pectoral fin. In larger individuals, blue stripe reduced, present only on snout. Juvenile (Fig. 7D, E) pigmentation same as adult except dark area distinctly tinged with more blue iridescence and terminating halfway along spinous dorsal fin (versus at end of spinous dorsal fin in adults), blue stripe on head much more prominent, and a second shorter blue stripe often present ventral to eye.

Coloration in freshly dead specimens (Fig. 8): Coloration similar to that of live specimens with little or no blue iridescence except in juveniles, where blue stripe through eye is visible. Paired fins, anal fin, and caudal fin pale to dusky, not vibrant white.

Coloration in preservation (Fig. 9): Base coloration of body pale yellow to golden brown, areas blue or grey in life dark brown; spinous dorsal fin uniformly dark brown, soft dorsal fin, anal fin, and pelvic fin dusky light grey, pectoral fin pale, caudal fin light brown at base becoming pale posteriorly.

(Fig. 1).Chromis vanbebberae occurs off Bermuda, the Florida Keys, the Bahamas, scattered sites in the northwest, central, eastern and southern Caribbean, and south to at least São Paulo, Brazil, including the offshore islands of Rocas Atoll, St. Paul Rocks, Trindade, and Fernando de Noronha.

Chromis vanbebberae occurs on a variety of deep-reef habitats at depths between 49 and at least 178 m, including on rocky reef slopes, coral outcroppings, around sponges, boulders, and caves. In areas of colder water in southeastern Brazil (Espírito Santo, Rio de Janeiro and Sao Paulo states) they are seen in depths as shallow as 10 m. In Curaçao, individuals are often found near sporadic patches of rocks located on otherwise open sandy bottoms devoid of other structure, which they frequently co-occupy with the seabasses Serranus phoebe or S. notospilus. They are also frequently found around artificial substrates such as shipwrecks (e.g., the wreck Queen of Nassau in southeast Florida), tires, and derelict ropes and fishing gear. This species and C. insolata Cuvier & Valenciennes, 1830, are the two most common pomacentrids on lower-mesophotic and rariphotic reefs in the Caribbean. In Brazil, C. insolata is replaced by its southern mesophotic counterpart, C. jubauna Moura, 1995, and the latter often schools with C. vanbebberae on coastal reefs; however, C. vanbebberae is the only mesophotic Chromis recorded in Brazilian oceanic islands.

Where C. vanbebberae and C. enchrysurus overlap in southeastern Florida, the two species segregate by depth, with C. enchrysurus occurring from (~ 25–40 m), and C. vanbebberae occurring in deeper water (~ 60–90 m). Emery and Smith-Vaniz (1982) reported a depth range of 5–146 m for C. enchrysurus, noting that most observations were from 40–70 m. The 146 m record was from Puerto Rico, and thus represents C. vanbebberae, not C. enchrysurus. Based on the confirmed records of C. enchrysurus from this study, the known depth range of that species is 5–97 m.

The species epithet vanbebberae, Latinized from Van Bebber, honors Barbara Van Bebber, one of the most accomplished submersible pilots in the Caribbean. Van Bebber was one of several skilled pilots of the ‘Curasub’ that assisted DROP with observations and collections of many new species, including this species. The common name “Whitetail Reeffish” (castañeta coliblanca in Spanish) refers to the caudal-fin coloration that distinguishes the species from Chromis enchrysurus, the Yellowtail Reeffish.

Chromis vanbebberae is easily distinguished from C. enchrysurus (Fig. 10) in having white versus yellow on the caudal fin, pelvic fins, anal fin, and posterior rays of the dorsal fin; however, this rapidly fades in death and preservation, making the two nearly indistinguishable. The two species are otherwise morphologically very similar, and species identity of preserved fishes can be most reliably determined based on locality of collection and genetics.

Chromis vanbebberae frequently co-occurs with C. insolata and C. scotti Emery, 1968, in the Caribbean, and with C. jubauna in Brazil. It can be distinguished from C. scotti in having an abrupt, diagonal dividing line between the dark dorsal portion of body and white ventral portion of the body (a diffuse horizontal dividing line in C. scotti), and in lacking the prominent iridescent light blue coloration that is present on most of the dorsal portion of the body of C. scotti (Fig. 11). In addition, the tail is dusky in C. scotti versus bright white in C. vanbebberae. The diagonal light/dark divide on the body of C. vanbebberae also distinguishes it from adult C. insolata, which has a horizontal division similar to C. scotti (Fig. 11). Chromis insolata and C. jubauna both differ from C. vanbebberae in number of anal rays: C. insolata typically possesses eleven anal rays and C. jubauna 9–11, in comparison to the typical 12 (rarely 11 or 13) of C. vanbebberae. In addition, C. insolata typically possesses 18–19 pored lateral line scales, whereas no C. vanbebberae specimens examined exceed 17. Adult C. jubauna have uniformly grey to black bodies with bright yellow caudal and soft dorsal fins, versus the dark/light bodies and white fins of C. vanbebberae. The juveniles of C. vanbebberae, C. insolata, C. scotti, C. enchrysurus, and C. jubauna also have dramatically different live coloration (Figs 7, 11). The juveniles of C. vanbebberae are similar to adults in coloration, except with slightly more blue iridescence, whereas juvenile C. scotti are almost entirely blue, juvenile C. insolata have prominent, wide yellow, purple, and white horizontal stripes, and juvenile C. jubauna are yellow dorsally and bright purplish-blue ventrally.