A new, mesophotic Coryphopterus goby (Teleostei, Gobiidae) from the southern Caribbean, with comments on relationships and depth distributions within the genus

Abstract A new species of western Atlantic Coryphopterus is described from mesophotic depths off Curaçao, southern Caribbean. Coryphopterus curasub sp. n., is similar to Coryphopterus dicrus in, among other features, having two prominent pigment spots of roughly equal intensity on the pectoral-fin base, the pelvic fins fused to form a disk, and no pelvic frenum. The two species can be differentiated by body depth (shallower in Coryphopterus curasub at origin of dorsal fin and caudal peduncle); differences in the pigmentation on the head, trunk, and basicaudal region; and usually by total number of rays (spinous plus soft) in the second dorsal fin (10–11, usually 11, in Coryphopterus curasub, 10 in Coryphopterus dicrus). Coryphopterus curasub differs from other Coryphopterus species that have a prominent pigment spot on the lower portion of the pectoral-fin base (Coryphopterus punctipectophorus and Coryphopterus venezuelae) in, among other features, lacking a pelvic frenum. Coryphopterus curasub was collected between 70 and 80 m, the deepest depth range known for the genus. Collections of Coryphopterus venezuelae at depths of 65–69 m extend the depth range of that species by approximately 50 m. Mitochondrial cytochrome c oxidase subunit I (COI) data corroborate the recognition of Coryphopterus curasub as a distinct species but do not rigorously resolve its relationships within the genus. A revised key to the western Atlantic species of Coryphopterus is presented.


Introduction
Coryphopterus gobies live in mostly shallow warm waters of the western Atlantic and eastern Pacific Oceans, dwelling on sand around coral and rocky reefs or hovering above or perching on reef structures. Twelve species are known from the western Atlantic and one from the eastern Pacific (Böhlke andRobins 1960, 1962;Thacker and Cole 2002;Victor 2007;Baldwin et al. 2009). Most Coryphopterus species inhabit depths < 40 m, but C. hyalinus Böhlke & Robins has been recorded to 52 m; C. eidolon Böhlke & Robins and C. thrix Böhlke & Robins to 54 m; C. dicrus Böhlke & Robins to 56 m; C. lipernes Böhlke and Robins to 60 m; C. glaucofraenum Gill to 61 m; and C. personatus (Jordan & Thompson) to 70 m (Böhlke andRobins 1960, 1962;Thacker and Cole 2002;Feitoza et al. 2005, Robertson andVan Tassell 2015). Published depth data for C. glaucofraenum, however, as well as that for C. tortugae (Jordan) (5-32 m) and C. venezuelae Cervigón (1-20 m), must be interpreted cautiously because of historical confusion about the taxonomy of this group, as should those of C. hyalinus and C. personatus for the same reason (Baldwin et al. 2009). Recent submersible diving to 300 m off Curaçao in the southern Caribbean as part of the Smithsonian Institution's Deep Reef Observation Project (DROP) resulted in the collection of three specimens of C. venezuelae at 65-69 m and four specimens of an unidentified Coryphopterus at 70-80 m. We describe the specimens from 70-80 m as a new species and comment on its relationships within the genus. Thacker and Cole (2002) investigated species relationships within Coryphopterus based on morphology and one mitochondrial gene (ND2). Their phylogeny suggests that Coryphopterus is restricted to the western Atlantic and eastern Pacific and that the Indo-Pacific genus Fusigobius, which Randall (1995) synonymized with Coryphopterus, is distinct. Based on study of the western Atlantic Lophogobius cyprinoides, Thacker and Cole (2002) and Thacker and Roje (2011) hypothesized that Coryphopterus is more closely related to Lophogobius than it is to Fusigobius. The eastern Pacific C. nicholsii (Bean), which is sister to Lophogobius + Coryphopterus in the phylogenies of Thacker and Cole (2002) and Thacker and Roje (2011), has been re-relegated to the monotypic genus Rhinogobiops Hubbs (Thacker 2011, Van Tassell 2011. A new western Atlantic species, Coryphopterus kuna Victor, was described in 2007 but not included in the molecular phylogeny of Thacker and Roje (2011). Further, neither C. tortugae nor C. venezuelae was included in previous phylogenetic work, even though both appear to be valid Coryphopterus species. Although Longley and Hildebrand (1941) and Böhlke and Robins (1960) considered C. tortugae (Jordan) to be a synonym of C. glaucofraenum, Garzón-Ferreira and Acero (1990) redescribed it as valid. Victor (2008) concurred and also described a variant of C. tortugae as new species, C. bol. Based on an integrative molecular and morphological analysis, Baldwin et al. (2009) also recognized C. tortugae as valid but relegated C. bol to the synonymy of C. venezuelae. In addition to the new species described here, tissue samples of all known Coryphopterus species except the Gulf of Mexico species C. punctipectophorus Springer are now available and were incorporated into the genetic analyses conducted in this study. As noted by Baldwin et al. (2009), Thacker andCole's (2002) DNA sequence from Belize previously thought to be from C. punctipectophorus (GenBank Accession No. AF391396) is actually from C. dicrus.

Materials and methods
Four specimens of the new species and three of C. venezuelae were collected using Substation Curaçao's (http://www.substation-Curacao.com) manned submersible Curasub. The sub has two flexible, hydraulic arms, one of which is equipped with a quinaldine-ejection system and the other with a suction hose. Anesthetized fish specimens were captured with the suction hose, which empties into a vented plexiglass cylinder attached to the outside of the sub. At the surface, the specimens were photographed, tissue sampled, and preserved. Preserved specimens were later photographed to document preserved pigment pattern and X-rayed with a digital radiography system. Counts and measurements follow Randall (2001). Format for dorsal-fin formula follows Birdsong et al. (1988). Head pore terminology follows Akihito et al. (1988). Measurements were made weeks to months after preservation and were taken to the nearest 0.1 mm with digital calipers or an ocular micrometer fitted into a Zeiss stereomicroscope.
Tissue samples for DNA Barcoding were stored in saturated salt-DMSO (dimethyl sulfoxide) buffer (Seutin et al. 1991). DNA extraction, PCR, sequencing cytochrome c oxidase subunit I (COI), and editing COI sequences were performed as outlined by Weigt et al. (2012a). A neighbor-joining tree (Saitou and Nei 1987) was generated using PAUP*4.1 (Swofford 2002) on an analysis of Kimura two-parameter distances (Kimura 1980). The neighbor-joining analysis reveals genetic distances in COI among individuals and clusters them into genetically distinct lineages, which, in teleost fishes, correspond well with species (e.g. Weigt 2012, Weigt et al. 2012b). Interspecific phylogenetic relationships were hypothesized for Coryphopterus based on maximum parsimony analysis of the COI sequences using heuristic searches in PAUP*4.1 (Swofford 2002). Characters were equally weighted and left unordered. The resulting equally parsimonious trees were summarized using the strict consensus method, and nodal support was estimated from 1,000 replicates of the bootstrap, utilizing random addition sequence and TBR branch swapping (Swofford 2002). The outgroup for the neighbor-joining analysis was a species of Fusigobius, a basal genus in the crested goby group that includes Coryphopterus, Lophogobius, and Rhinogobiops (Thacker and Roje 2011). Outgroups for the parsimony analysis were Fusigobius and Rhinogobiops.
GenSeq nomenclature (Chakrabarty et al. 2013) and GenBank accession numbers for DNA sequences derived in this study are presented along with museum catalog numbers for voucher specimens in the Appendix. GenBank accession numbers for Coryphopterus sequences included in the analyses that were published by Baldwin et al. (2009) are GQ367306-GQ367475, and those for Lophogobius cyprinoides sequences published by Weigt et al. (2012b)  Generic assignment. The combination of six spines in the first dorsal fin, fewer than 20 rays in the second dorsal fin, pelvic fin with one spine and five soft rays, head pores present, no free pectoral-fin rays, no scales on top of head, and no prominent crest on top of head anteriorly from first dorsal fin support the placement of C. curasub in the genus Coryphopterus (Murdy 2002).
Diagnosis. A species of Coryphopterus distinguishable from its congeners by the following combination of characters: total second dorsal-fin rays (spinous plus soft) 10-11, usually 11; total anal-fin rays (spinous plus soft) 10; pectoral-fin rays 19-20; pelvic fins united; no pelvic frenum; pectoral-fin base with two prominent dark spots (yellow with dark spotting in life) of roughly equal intensity, one on dorsal portion of fin base and one on ventral part; no distinct black blotch behind orbit above opercle; no dark triangular blotch immediately behind middle of orbit; blotches of pigment on trunk mostly yellow; few melanophores and yellow dots interspersed among yellow blotches of pigment on trunk; no black ring of pigment surrounding anus; dark triangular blotch variously developed beneath anteroventral corner of orbit; basicaudal blotch cross-shaped, with prominent anterior projection; and two yellow/orange blotches on base of caudal fin situated immediately behind basicaudal blotch.
Trunk, belly, and pre-pelvic region scaled, head and predorsal region naked; scales ctenoid except on pre-pelvic region, where they are cycloid. Upper jaw with several rows of small conical teeth, outermost teeth largest but smaller than outermost dentary teeth; dentary with outer row of fairly large conical teeth and several inner rows of smaller teeth; innermost teeth intermediate in size between teeth of outermost row and those adjacent to it. No teeth on vomer, palatines, or pterygoids. Anterior nare opening on short tube; posterior nare a simple opening. Head pores prominent: nasal pore, anterior interorbital pore, posterior interorbital pore, infraorbital pore, postorbital pore, pore at each end of lateral sensory canal, pore at each end of posterior lateral canal, and three preopercular pores (pores B', C and D [both single], E, F, G, H', K', L', M', N, O'). A very low, thin ridge of tissue extending from just posterior to interobital region to base of first dorsal fin.
When photographed against a light background ( Fig. 2A), the following color pattern visible in holotype. TRUNK: ground color white, several irregular horizontal rows of yellow/orange irregular-shaped blotches, most blotches bordered by and peppered with small black melanophores; uppermost row comprising approximately 11 blotches distributed along dorsal body margin from head (with two-three blotches) to caudal Figure 2. Comparison of A Coryphopterus curasub sp. n., holotype, USNM 406373, 33.3 mm SL, and its most similar congener B Coryphopterus dicrus, USNM 413296, 30 mm SL. Note the differences in the shape of the basicaudal pigment marking (with distinct anterior projection in C. curasub), body depth (shallower in C. curasub), head pigment (absence of a distinct blotch of black pigment immediately posterior to the orbit and presence of a black triangle of pigment beneath the anteroventral portion of orbit in C. curasub (present and absent, respectively, in C. dicrus), and trunk pigment (blotches predominantly yellow with few melanophores interspersed among them in C. curasub vs. blotches predominantly orange/ rust with numerous melanophores interspersed among them in C. dicrus).
peduncle; second row shortest, comprising approximately eight blotches and extending from just posterior to posterodorsal margin of orbit to vertical through third or fourth dorsal-fin spine; third row comprising approximately 15 blotches and extending from middle of posterior margin of orbit to caudal peduncle-anterior blotches of this row united to form irregular stripe; lowermost row comprising five prominent blotches that extend from vertical through anterior origin of second dorsal fin to posterior portion of caudal peduncle and several less conspicuous blotches anterior of and within this series; this row continuing anteriorly onto pectoral-fin base and head as an irregular yellow stripe that passes along ventral margin of orbit and terminates on posterior end of upper jaw; yellow blotches on anterior portion of trunk and head better defined by peripheral melanophores than those on posterior portion of trunk; scattered small spots of yellow/black pigment interspersed among blotches in most rows. HEAD: head pigment also including short yellow/black stripe on snout; yellow stripe on ventral portion of head from posterior end of lower jaw to preopercle; triangle of black pigment beneath anteroventral margin of orbit; scattered black dots on upper lip, on snout, and beneath eye; two small black blotches of pigment on operculum; some whitish pigment extending posterodorsally from dark triangle beneath orbit; pu-pil black, iris brown; ventral portions of head and trunk mostly white except for streak of yellow pigment beneath opercular opening. CAUDAL PEDUNCLE: dark crossshaped basicaudal blotch present on central portion of caudal peduncle and caudal-fin base, the anterior projection of cross prominent; two yellow spots bordering dorsal and ventral ends of blotch posteriorly and extending onto bases of several caudal-fin rays. FINS: first dorsal fin translucent, with three irregular yellow stripes; second dorsal fin with three or four irregular yellow stripes; anal fin with broad stripe of pale yellow pigment on middle of fin; caudal fin with blotches of yellow pigment forming an arc on basal portion of fin, some of this pigment extending distally along caudal rays as barely noticeable yellow streaks; pectoral and pelvic fins mostly clear; yellow/black blotch on dorsal portion of pectoral-fin base extending onto basal portion of dorsalmost pectoral rays; lower portion of pectoral-fin base with well-defined, round, yellow/orange blotch with dark dots. When photographed against a black background (Fig. 1B), numerous small, white, round to oblong spots visible on membranes of all fins; distal margin of anal fin with pale blue stripe.
Male paratypes (Fig. 1C) with similar coloration except black triangle of pigment beneath anteroventral corner of eye less conspicuous; melanophores present on lower jaw; iris mottled whitish/bronze; pectoral fin with pale yellow pigment; and pelvic fin with black-spotted yellow patches. IMMATURE SPECIMEN (Fig. 1D) paler but with most pigment described above developing; diagnostic cross-shaped marking on caudal peduncle not formed, and only lower black-spotted yellow blotch on pectoralfin base well formed; most prominent pigment comprising yellow stripes on head, five black-spotted yellow blotches on trunk in lowermost row, and black-spotted yellow blotch in line with this row on base of caudal fin.
Color of holotype in alcohol (Fig. 1A). Ground color of head and trunk light tan, overlain by assorted dark circles, stripes, and irregular markings. Scattered melanophores and blotches present along base of spinous dorsal fin and on dorsal portion of trunk. Most prominent trunk pigment located just ventral to lateral midline as a row of six mostly circular blotches of roughly equal size except the second from anterior and last, which are small relative to the others; this row of pigment markings originating at a vertical through second element of second dorsal fin and terminating on caudal peduncle. Head with several circular blotches in row posterior to posterodorsal portion of orbit; irregular stripe of pigment extending posteriorly from middle of orbit; irregular stripe-like mark extending posteriorly from posteroventral portion of orbit; scattered melanophores on snout, lacrimal, and upper jaw; dark triangle of pigment beneath anteroventral corner of orbit; and two irregular streaks of pigment on ventral portion of operculum. Dark portion of basicaudal blotch as described above, but no melanophores present on remainder of caudal fin or on anal and pelvic fins. First dorsal fin with small bits of dark pigment on membranes of second, third and fifth spines. Pectoral-fin base with one dorsal and one ventral circular blotches, the former extending as short series of melanophores posteriorly onto bases of dorsal rays of fin.

Distribution.
Known from 70-80 m off Curaçao, southern Caribbean. Habitat. Notes recorded during the submersible dive on which the 33.0 mm SL paratype (USNM 431328) was collected indicate that it occurred on sand with rubble patches on a 45°slope.
Etymology. Named for the manned submersible Curasub, which is owned and operated by Substation Curaçao, in recognition of the contributions of this vehicle to increasing our knowledge of the Caribbean deep-reef fish fauna.
Common name. "Yellow-spotted sand goby" refers to the yellow spots on the trunk and the collection habitat.
Morphological comparisons. Coryphopterus curasub is most similar to C. dicrus (Fig. 2) and keys to that species in the most recent dichotomous key to western Atlantic Coryphopterus (Baldwin et al. 2009). They share the presence of two dark circular markings on the pectoral-fin base that are of roughly equal intensity (except in the juvenile C. curasub, in which only the lower spot is prominent), the absence of a distinct black blotch or triangle of pigment behind the eye above the opercle in adults, the presence of a united pelvic fin in which the fourth rays are longer than the fifth, and the absence of a pelvic frenum. They usually differ in total number of rays (spinous plus soft) in the second dorsal fin (10-11, usually 11, in C. curasub, 10 in C. dicrus); absence of a dark triangular blotch immediately posterior to the orbit in C. curasub (present in C. dicrus); presence of a dark triangular blotch beneath the anteroventral portion of the orbit in the largest specimen (33.3 mm SL holotype) of C. curasub (absent in similarly large specimens of C. dicrus); blotches of pigment on the trunk typically yellow in C. curasub, orange to rusty brown in C. dicrus; few yellow spots with tiny melanophores among the yellow blotches of pigment on the trunk in C. curasub vs. many rusty spots with tiny melanophores between the rusty brown blotches in C. dicrus; configuration of the basicaudal blotch (a cross-shaped blotch with a distinct anterior projection in C. curasub vs. a dumbbell-shaped bar in C. dicrus); the two yellow/ orange blotches on the base of the caudal fin situated immediately behind the basicaudal blotch in C. curasub vs. superimposed on and contributing to the upper and lower heads of the basicaudal bar of C. dicrus; maximum body depth from base of spinous dorsal fin (17-19% SL in C. curasub, 20-26% SL in C. dicrus -Böhlke and Robins 1960); least depth of caudal peduncle (11-12% SL in C. curasub, 13-15% SL in C. dicrus -Böhlke and Robins 1960). Coryphopterus curasub differs from all other western Atlantic Coryphopterus (C. alloides Böhlke & Robins, C. eidolon, C. glaucofraenum, C. hyalinus, C. kuna, C. lipernes, C. personatus, C. punctipectophorus, C. thrix, C. tortugae, and C. venezuelae) in having two round dark marks on the pectoral-fin base that are of roughly equal intensity in adults. It further differs from C. hyalinus, C. lipernes, and C. personatus in lacking a black ring around the anus; from those species and C. alloides in having the pelvic fin united; from C. glaucofraenum, C. tortugae, and C. venezuelae in lacking both a pelvic frenum and a distinct black blotch or triangle behind the eye above the opercle; and from C. kuna in having 10 or 11 total second dorsal-fin rays, 10 total anal-fin rays, and 19-20 pectoral-fin rays (vs. 9, 9, and 15, respectively).
Of the 14 apomorphic morphological characters of Coryphopterus species tabulated by Thacker and Cole (2002) for inclusion in their phylogenetic analysis of the genus, C. curasub has (character 1) no pelvic frenum, (3) the fifth (innermost) pelvic-fin ray shortened relative to the fourth, (4) a low ridge of tissue on top of the head, (8) orange or gold coloration on the body, and (10) three stripes of pigment on the head. The presence of a low ridge of tissue on the head characterizes all Coryphopterus species and is thus uninformative. Likewise, although Thacker and Cole (2002) scored most species as lacking orange or gold coloration, in a more thorough analysis of fresh color patterns in western Atlantic Coryphopterus, Baldwin et al. (2009) noted the presence of yellow/orange/gold pigment in all species. Coryphopterus curasub shares with C. dicrus, C. alloides, C. personatus, C. hyalinus, and C. lipernes the absence of a pelvic frenum, with those taxa and C. eidolon a shortened fifth pelvic-fin ray (relative to the fourth), and with C. eidolon, C. thrix, C. dicrus, C. glaucofraenum, C. tortugae, C. venezuelae, C. urospilus, and C. punctipectophorus the presence of three stripes of pigment on the head. In C. curasub, the lowermost stripe (on the cheek) is yellow and lacks melanophores, which are present in the other species. The homology of the pigment stripes is thus questionable. Thacker and Cole (2002) list several apomorphic characters (11-13) related to basicaudal pigment, but the configuration of the basicaudal blotch in C. curasub is unique among Coryphopterus species. Thacker and Cole's (2002) 14 th character, the presence or absence of a pigment spot on the pectoral-fin base, insufficiently describes the variation in this character in Coryphopterus. Of the various configurations-no spots, one spot dorsally, one spot ventrally, two spots with upper spot more intense, two spots of roughly equal intensity-only C. curasub and C. dicrus have two spots of equal intensity among Coryphopterus species and outgroup taxa. In summary, of the potentially informative, putative apomorphic characters exhibited by C. curasub, only C. dicrus shares all of them.
Genetic comparisons. COI sequences derived from tissue samples from the four type specimens of C. curasub and three specimens of C. venezuelae collected by submersible as part of this study (Appendix) were combined with 173 previously published COI sequences for western Atlantic Coryphopterus (Baldwin et al. 2009, Weigt et al. 2012b) in a neighbor-joining analysis (Fig. 3). Intraspecific divergence in COI for C. curasub was 0.1% as compared to 17-23% interspecific divergence between C. curasub and other western Atlantic Coryphopterus species, including C. dicrus (18%, Table 1). Intraspecific divergences for all western Atlantic Coryphopterus species were < 1% except for C. alloides (3.7%), likely reflecting, as suggested by Baldwin et al. (2009), a cryptic species that awaits investigation. Phylogenetic relationships within Coryphopterus were analyzed using a reduced COI dataset of western Atlantic Coryphopterus (43 ingroup sequences selected from the entire COI data set to maximize geographical coverage of each species), the eastern Pacific C. urospilus, and the western Atlantic Lophogobius cyprinoides. A strict consensus of 24 trees resulting from a maximum parsimony analysis (Fig. 4) does not resolve the relationships of C. curasub with confidence. A clade comprising C. venezuelae, C. glaucofraenum, and C. tortugae is strongly supported (99%), as are clades comprising C. venezuelae and C. glaucofraenum (80%), the hovering species C. hyalinus and C. personatus (100%), and the planktivores C. lipernes + C. hyalinus + C. personatus (63%). As noted by Thacker and Cole (2002) based on ND2 mitochondrial and morphological data, Lophogobius is closely related to Coryphopterus, here appearing in a poorly supported clade that also comprises C. dicrus and the eastern Pacific C. urospilus. Adding more loci to the genetic analysis as well as C. punctipectophorus and the eastern-and Indo-Pacific species of Lophogobius may help resolve interspecific  Coryphopterus curasub, which is known from 70-80 m, is the only member of the genus that has a narrow depth range completely confined to mesophotic depths. Coryphopterus venezuelae, C. glaucofraenum, C. dicrus, C. eidolon, C. thrix, C. hyalinus, C. lipernes, and C. personatus inhabit depths as deep as 52-70 m, but they have broad depth ranges that extend as shallow as 1-6 m. The only Coryphopterus species in addition to C. curasub that we have collected using the Curasub submersible are C. hyalinus -one specimen from 33 m, and C. venezuelae -three specimens from 65-69 m. Prior to this study, C. venezuelae was known from 1-20 m (Robertson and Van Tassell 2015), and thus our new collections of the species off Curacao extend its known range by nearly 50 m.  Böhlke andRobins (1960, 1962); Thacker and Cole (2002); Feitoza et al. (2005); Robertson and Van Tassell (2015); the Florida Museum of Natural History online fish catalog -http://specifyportal.flmnh.ufl.edu/fishes/; the Florida Fish and Wildlife Conservation Commission online catalog http://myfwc.com/research/saltwater/specimen-collections/sis/ichthyology/; the Smithsonian National Museum of Natural History online catalog -www. vertebrates.si.edu//search/fishes); and this study. Body usually pale, pigment primarily comprising three rows of markings on side of body; lower row comprising small, mostly vertically elongate markings, some of which may be crescent shaped or some part of an X-shape but rarely well-defined X's; height of any X-shaped markings considerably less than eye diameter; pigment mark above opercle usually a triangle, and basicaudal pigment usually a central bar .......................Coryphopterus tortugae -Body heavily pigmented or pale but no vertically elongate or crescent-shaped markings in ventral row of pigment on side of body; height of any X-shaped markings three-quarters of or equal to eye diameter; pigment mark above opercle triangular, rounded, or with two peaks; basicaudal pigment variable: two separate spots, a vertical dumbbell, a central bar, or a C-shaped marking ..... 12 12

Revised key to the Western Atlantic species of Coryphopterus
Pectoral-fin base with dark spot or rectangle ventrally (may be associated with bright yellow pigment in life); one or two bars or blotches sometimes present dorsally; three rows of dark markings on side of body, some in lower row large, X-shaped markings in heavily pigmented specimens, small, circular blotches in paler specimens; pigment mark above opercle triangular or round .

Discussion and conclusions
Exploratory submersible diving to 300 m off Curaçao is resulting in the discovery of numerous new fish species, only a few of which have been described to date Robertson 2013, 2014;Baldwin and Johnson 2014). In addition to the new Coryphopterus described here, numerous seven-spined gobies that represent undescribed species in the Chriolepis/Psilotris/Varicus group have been collected, as have several new species of Lythrypnus-like gobies and a putative new species of Palatagobius. A new genus and species of deep-reef goby, Antilligobius nikkiae Van Tassell, Tornabene, and Colin, was recently described from deep reefs at several localities in the Caribbean (including Curaçao) and Bahamas . Deep-reef fish faunas in general have been poorly studied globally, and the recent new-species discoveries suggest that our knowledge of the deep-reef gobiid fauna in the southern Caribbean, and likely circumglobally, is far from complete. One question of interest is whether deepreef species generally represent single offshoots of largely shallow-reef clades or form natural evolutionary groups. Antilligobius nikkiae, which inhabits depths of 73-150 m, appears to have its closest relative in shallower water than it inhabits. Rüber et al. (2003) hypothesized that Antilligobius belongs within the monophyletic Microgobius group of the tribe Gobiosomatini, specifically as the sister group of the monophyletic Microgobius. Tornabene et al. (2012) tabulated depth distributions for Microgobius species, which occur from < 1 m to at least 75 m, but most occur at depths < 20 m. The COI data analyzed in this study do not rigorously resolve relationships among Coryphopterus species, but morphological data suggest that C. curasub may be most closely related to C. dicrus. Depth ranges of those species (1-56 m for C. dicrus, 70-80 m for C. curasub) do not overlap, suggesting that if they are sister species, depth-mediated speciation may have been involved in their evolution. Additional morphological and genetic analyses of Coryphopterus and other goby genera are in progress in efforts to investigate patterns of speciation and historical invasions of deep tropical reefs. Filling gaps in our knowledge of deep-reef species diversity is critical to meaningful hypotheses about the evolution of the deep-reef fauna, and we therefore continue to seek funding for exploratory diving aboard the Curasub.