Introduction

The deepwater cardinalfish genus Epigonus Rafinesque 1810 is the most species-rich and widely distributed genus in the family Epigonidae, with 40 valid species (Mayer 1974; Abramov 1992; Okamoto and Miyamoto 2022). In several taxonomic studies of Epigonus, the first author proposed four species groups (Okamoto 2011, 2012; Okamoto and Motomura 2011, 2013): the Epigonus constanciae group, the Epigonus oligolepis group, the Epigonus pandionis group, and the Epigonus telescopus group. Recent taxonomic studies of the genus have focused on the Indo-Pacific region (Okamoto 2018; Okamoto and Gon 2018; Okamoto et al. 2020; Okamoto and Miyamoto 2022), and study in the western Atlantic Ocean has not progressed since Mayer (1974). Previous submersible diving off Curaçao in the southern Caribbean as part of the Smithsonian’s Deep Reef Observation Project (DROP) collected two species of Epigonus that are morphologically distinct from currently known species. These species are described herein, and a key to the species in the Caribbean Sea is provided.

Materials and methods

Specimens were collected on dives made in 2012–2014 in the human-occupied submersible Curasub (http://www.substation-Curacao.com). Fish specimens were collected using the fish anesthetic quinaldine pumped from a reservoir through a tube attached to one hydraulic arm of the sub and a suction hose attached to the other arm. The hose empties into a vented plexiglass cylinder attached to the outside of the sub. At the surface, some specimens were measured, photographed, tissue sampled (muscle biopsy from right side) and preserved.

Meristic and morphometric methods followed Mayer (1974) and Okamoto (2011). Missing lateral-line scales were estimated by counting scale pockets. The number of pored lateral-line scales on the caudal fin is represented as “+ n”. The first caudal vertebra is defined as the first vertebra bearing a definite hemal spine. Measurements were made with calipers to the nearest 0.1 mm. Terminology and formula of the supraneural bones follows Mabee (1988) and Ahlstrom et al. (1976), respectively. Counts of supraneurals, vertebrae, and ribs were taken from radiographs. The term “maxillary mustache-like process” is used for a process on the maxillary head (see Okamoto 2011: fig. 3). The number of pyloric caeca and sex were established by dissection of the abdomen on the right side. Standard length is abbreviated as SL. Institutional codes follow Sabaj (2020).

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. (2012). Sequences were uploaded to the Barcode of Life Database (Bin Numbers BOLD: ACG7476 and BOLD: ACG7477, boldsystems.org) and Genbank (Accession numbers OR918549–OR918570), and sequences of the holotypes of the two species were entered into the BOLD search engine for comparison with other available sequences of Epigonus.

Epigonus gemma sp. nov.

(Figs. 1, 2)

Fig. 1
figure 1

Epigonus gemma sp. nov. a USNM 431654, holotype, 76.7 mm SL, preserved specimen; b USNM 413854, paratype, 71.5 mm SL, fresh specimen (photographed by C. C. Baldwin); c USNM 413858, paratype, 62.6 mm SL, radiograph

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Fig. 2
figure 2

Lateral view of mouth of Epigonus gemma sp. nov., USNM 413854, paratype, 71.5 mm SL. Arrow shows enlarged conical teeth on symphysis of lower jaw

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Holotype. USNM 431654, 76.7 mm SL, male, DNA #CUR14082, Curasub submersible, sta. 14-12, Curaçao, east of downline at Substation Curaçao, 12°05.00′N, 68°53.57′W, 275 m depth, 16 September 2014, C. Baldwin, L. Weigt, B. Van Bebber, R. Betancur.

Paratypes. 6 specimens: USNM 413854, 71.5 mm SL, male, DNA #CUR12009, Curasub submersible, sta. 12-01, Curaçao, off Substation Curaçao downline, 12°04.59′N, 68°53.56′W, 171–309 m depth, 21 May 2012, C. Baldwin, A. Schrier, B. Brandt; USNM 413858, 62.6 mm SL, male, DNA #CUR12088, USNM 413859, 54.7 mm SL, sex unknown, DNA #CUR12089, USNM 413861, sex unknown, DNA #CUR12091, Curasub submersible, sta. 12-12, Curaçao, east of downline at Substation Curaçao, 12°04.59′N, 68°53.56′W, 156–290 m depth, 7 August 2012, C. Baldwin, A. Schrier, D. Pawson; USNM 413862, 53.5 mm SL, sex unknown, DNA #CUR12296, Curasub submersible, sta. 12-18, Curaçao, off Substation Curaçao downline, 12°04.59′N, 68°53.56′W, 291–294 m depth, 14 August 2012, A. Schrier, B. Brandt, C. Baldwin, A. Driskell; USNM 431690, 76.1 mm SL, male, DNA #CUR14082, Curasub submersible, sta. 14-09, Curaçao, east of downline at Substation Curaçao, 12°04.59′N, 68°53.56′W, 265–293 m depth, 24 June 2014, C. Baldwin, B. Brandt, A. Schrier.

Diagnosis. A species of Epigonus with the following combination of characters: dorsal-fin rays VII-I, 9–10; pectoral-fin rays 16; total gill rakers 25–27; vertebrae 10 + 15; pyloric caeca 8–9; pored lateral-line scales 43–44 + 5–6; opercular spine absent; maxillary mustache-like processes absent; ribs on last abdominal vertebra absent; tongue toothless; endopterygoid teeth absent; enlarged conical teeth on symphysis of lower jaw present.

The DNA barcode for the holotype (USNM 431654) is as follows: NNNNNNNNNNNNNNNNNNNNNNNCCTTTATCTCGTATTTGGTGCTTGAGCCGGAATAGTGGGCACAGCCTTAAGCCTGCTTATTCGGGCAGAACTCAGCCAACCAGGCGCCCTCCTCGGAGACGACCAGATCTATAACGTAATTGTTACAGCACACGCCTTCGTAATAATTTTCTTTATAGTAATACCAATTATGATTGGGGGCTTCGGAAATTGGCTTATCCCTTTAATAATTGGGGCCCCTGATATAGCCTTCCCTCGAATAAATAATATAAGCTTTTGACTCCTCCCTCCTTCCTTCCTGCTCCTTCTTGCCTCTTCTGGGGTAGAAGCCGGTGCCGGCACCGGCTGAACAGTTTACCCCCCTCTGGCTGGGAACTTAGCCCACGCGGGGGCCTCTGTTGATTTAACAATCTTTTCTCTACATCTTGCAGGTATTTCCTCAATTCTTGGGGCTATTAACTTTATTACAACAATTATTAATATAAAACCCCCGGCCATTTCACAATACCAAACACCCCTGTTTGTGTGAGCAGTATTAATTACCGCAGTTCTTCTTCTGCTGTCCCTCCCTGTCCTTGCTGCTGGAATTACAATGCTTCTTACAGACCGAAACCTCAACACCACCTTCTTTGACCCGGCAGGAGGAGGGGACCCCATCCTCTACCAACACCTGTTTNNNNNNNNNN.

Description. Counts and proportional measurements are given in Table 1. Data for the holotype are presented first, followed by data of paratypes (if different) in parentheses. Body moderately slender, laterally compressed, nape slightly humped, deepest at pectoral-fin base (Fig. 1). Head large, laterally compressed. Maxillary mustache-like process absent. Snout short and round; two nostrils close-set without dermal flap, anterior nostril short and with membranous tube, posterior nostril elliptical. Eye large, round, diameter slightly shorter than postorbital length (subequal); bony rim of orbit slightly raised above dorsal profile; interorbital region flat. Mouth large, terminal, gape oblique; posterior margin of maxilla extending to below anterior margin of pupil; lower jaw slightly projecting when mouth closed; nob-like structures absent on symphysis of lower jaw. Upper jaw teeth small conical, arranged in a single series visible when mouth closed. Lower jaw teeth small conical, arranged in a single series; tip of lower jaw curved slightly upward, symphysis forming a thick bony projection, three enlarged conical teeth on each side of symphysis of lower jaw (one to three enlarged conical teeth on each side of symphysis of lower jaw; Fig. 2). Small number of villiform teeth present on vomer. Single row of small conical teeth (rarely two rows) on palatines. Tongue and endopterygoid toothless. Opercular spine absent; preopercle without spines, ventral and posterior margins smooth. Origin of first-dorsal fin located behind base of pelvic fin; first dorsal-fin spine minute; fourth dorsal-fin spine the longest, length longer than orbital diameter; two supernumerary spines on first dorsal pterygiophore. Spine of second dorsal fin long. First and second dorsal fins separated by gap longer than snout length. Origin of anal fin vertically below 4th soft ray of second dorsal-fin; first anal-fin spine minute; second spine long, length longer than orbital diameter; two supernumerary spines on first anal pterygiophore. Pectoral fin short, posterior tip of fin not reaching to vertical line from anus. Pelvic fin long, posterior tip just before to anus. Caudal fin deeply forked. Anus located vertically below origin of second dorsal-fin base. Ribs absent on last abdominal vertebra (Fig. 1c). Supraneural bones 3 (/0+0/0+2/1+1/1/). Scales deciduous, small, weakly ctenoid, covering the whole body except snout tip, anterior to rim of orbit, and surface of jaws; scales also present on bases of second dorsal, anal and caudal fins; series of pored lateral-line scales complete, 5 (5–6) pored scales on caudal fin. No trace of luminous organ around belly or pyloric caeca.

Table 1 Counts and measurements of Epigonus gemma sp. nov. and Epigonus hexacanthus sp. nov.
Full size table

Color when fresh (Fig. 1b). Dorsal portions of body and head light purple; ventral surface and lower half of body silvery-tan. All fins light black. Gill cover light blue, posterior margin black.

Color in alcohol (Fig. 1a). Body and head uniformly light brown, except for the snout and gill cover which are dark gray. Dorsal, anal, pelvic, and caudal fins dark gray, with many melanophores on the soft rays and membranes. Pectoral fin light gray except for dark base. Mouth cavity tan.

Distribution. Known only from Curaçao, southern Caribbean.

Habitat. Epigonids are common at Curaçao at depths near the lower limit of the Curasub (300 m), especially in caves and crevices along a near-vertical rock wall [Electronic Supplementary Material (ESM) Video S1]. All specimens described in this study, including those of E. gemma sp. nov., were collected in this habitat.

Etymology. The specific name gemma is from the Latin meaning bud, in reference to the enlarged conical teeth on each side of the symphysis of the lower jaw (Fig. 2).

Comparison. Epigonus gemma sp. nov. belongs to a group of similar species in the E. pandionis group (Okamoto and Motomura 2013). The E. pandionis group is distinguished from the other three species groups of the genus (the E. constanciae group, E. oligolepis group, and E. telescopus group) in having more than 43 pored lateral-line scales, lacking an opercular spine, and having VII-I, 9–11 dorsal-fin rays (Okamoto and Motomura 2013). Okamoto and Motomura (2013) indicated that the E. pandionis group comprises nine species, viz., Epigonus cavaticus Ida et al. 2007; Epigonus denticulatus Dieuzeide 1950; Epigonus elongatus Parin and Abramov 1986; Epigonus fragilis (Jordan and Jordan 1922); Epigonus lifouensis Okamoto and Motomura 2013; Epigonus marisrubri Krupp et al. 2009; Epigonus pandionis (Goode and Bean 1881); Epigonus parini Abramov 1987; and Epigonus tuberculatus Okamoto and Motomura 2013. Epigonus gemma sp. nov. is unique in the group in having enlarged conical teeth on each side of the symphysis of lower jaw (vs. absent).

In addition, E. gemma sp. nov. can be distinguished from E. denticulatus, E. elongatus, E. lifouensis, E. marisrubri, E. pandionis, E. parini, and E. tuberculatus by having 16 pectoral-fin rays and 25–27 gill rakers (vs. 18–21 and 28–34, respectively in E. denticulatus; 18–20 and 28–34 in E. elongatus; 18–19 and 24–25 in E. lifouensis; 17–18 and 29–30 in E. marisrubri; 17–19 and 26–30 in E. pandionis; 18–20 and 35–39 in E. parini; and 19–20 and 21–22 in E. tuberculatus; Okamoto and Motomura 2013, table 2). Epigonus cavaticus and E. fragilis are similar to E. gemma sp. nov. in having overlapping pectoral-fin rays and gill rakers but differ from E. gemma sp. nov. in having a large number of pored lateral-line scales (48–50 in E. cavaticus and 46–49 in E. fragilis vs. 43–44 in E. gemma sp. nov.) and a pair of ribs on the last abdominal vertebra (vs. absent in E. gemma sp. nov.; Fig. 1c). Epigonus gemma sp. nov. is distinguished from the second new species in the present study, Epigonus hexacanthus sp. nov., in having enlarged conical teeth on symphysis of lower jaw (vs. absent in E. hexacanthus), 7 spines on the first dorsal-fin (vs. 6 spines), and 43–44 lateral-line scales (vs. 32–35 lateral-line scales).

Remarks. Within Epigonus, only Epigonus exodon Okamoto and Motomura 2012 and Epigonus glossodontus Gon 1985 have the enlarged conical teeth on each side of the lower-jaw symphysis present in E. gemma (Okamoto and Gon 2018; Okamoto et al. 2020). Epigonus exodon has been reported to undergo growth changes in those teeth (Okamoto and Motomura 2012), but no growth changes in those teeth were found in E. gemma sp. nov. between 37.3 mm SL and 76.7 mm SL.

The holotype and seven paratypes of E. gemma sp. nov. are males of 62.6–76.7 mm SL with a large testis. The sex of the remaining type specimens was unknown. Although no mature eggs were found, the present species is most likely a small species.

The DNA barcode of the holotype, USNM 431654, clusters in BOLD with six other sequences of E. gemma sp. nov. from Curaçao (USNM 413854, 413858, 413859, 413861, 413862, 431690). That lineage is approximately 5% divergent from “Epigonus sp.” from India (accession number: GBMND26919-21, GBMND26920-21, and GBMND26921-21) and 11% divergent from Epigonus hexacanthus sp. nov. From other species of Epigonus known from the Caribbean Sea that are represented in the BOLD database [E. denticulatus, Epigonus macrops (Brauer 1906), E. pandionis], the barcode of E. gemma differs by more than 17%. Intraspecific divergence in COI sequences for E. gemma is < 0.5%.

Epigonus hexacanthus sp. nov.

(Figs. 3, 4)

Fig. 3
figure 3

Epigonus hexacanthus sp. nov. a USNM 422678, holotype, 54.4 mm SL, preserved specimen; b USNM 413950, paratype, 44.1 mm SL, fresh specimen (photographed by C. C. Baldwin); c USNM 431760, paratype, 56.3 mm SL, radiograph

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Fig. 4
figure 4

In situ image of Epigonus hexacanthus sp. nov. taken by the submersible Curasub on 23 May 2013, at 265 m near the bottom of rock wall at Curaçao (photographed by C. C. Baldwin and D. R. Robertson)

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Holotype. USNM 422678, 54.4 mm SL, female, DNA #CUR13115, Curasub submersible, sta. 13-06, Curaçao, east of downline at Substation Curaçao, 12°04.59′N, 68°53.56′W, 265 m depth, 23 May 2013, D. Robertson, M. Harasewych, C. Castillo, B. Brandt.

Paratypes. 11 specimens: USNM 413950, 44.1 mm SL, female, DNA # CUR13064, USNM 413951, 42.8 mm SL, male, Curasub submersible, sta. 13-01, Curaçao, off Substation Curaçao downline, 12°04.59′N, 68°53.56′W, 52–304 m depth, 5 February 2013, C. Baldwin, L. Weigt, L. Wacchaus, B. Brandt, J. Piraino; USNM 426792, 33.3 mm SL, sex unknown, DNA #CUR13295, Curasub submersible, sta. 13-21, Curaçao, off Substation Curaçao downline, 12°04.59′N, 68°53.56′W, 247 m depth, 17 August 2013, C. Baldwin, A. Schrier, B. Brandt, A. Driskell; USNM 431707, 50.1 mm SL, female, DNA #CUR14099, Curasub submersible, sta. 14-12, Curaçao, east of downline at Substation Curaçao, 12°05.00′N, 68°53.57′W, 265 m depth, 16 September 2014, C. Baldwin, L. Weigt, B. Van Bebber, R. Betancur; USNM 431760, 7 specimens, 56.3 mm SL, female, 47.4 mm SL, female, 47.0 mm SL, female, 44.0 mm SL, female, 37.6 mm SL, female, 35.8 mm SL, male, 32.3 mm SL, male, Curasub submersible, sta. 14-12, Curaçao, east of downline at Substation Curaçao, 12°05.00′N, 68°53.57′W, 275 m depth, 16 September 2014, C. Baldwin, L. Weigt, B. Van Bebber, R. Betancur.

Non-type specimens. 10 specimens (all specimens were subjected to DNA analysis). USNM 413848 (44.0 mm SL, DNA #CUR12003), USNM 413849 (46.0 mm SL, DNA #CUR12004), USNM 413850 (49.0 mm SL, DNA #CUR12005), USNM 413851 (35.0 mm SL, DNA #CUR12006), USNM 413852 (37.0 mm SL, DNA #CUR12007), USNM 413853 (33.0 mm SL, DNA #CUR12008), USNM 413855 (34.0 mm SL, DNA #CUR12014), USNM 413857 (40.0 mm SL, DNA #CUR12016), Curasub submersible, sta. 12-01, Curaçao, off Substation Curaçao downline, 12°04.59′N, 68°53.56′W, 171–309 m depth, 21 May 2012, C. Baldwin, A. Schrier, B. Brandt; USNM 413860, 50.0 mm SL, DNA #CUR12090, Curasub submersible, sta. 12-12, Curaçao, east of downline at Substation Curaçao, 12°04.59′N, 68°53.56′W, 156–290 m depth, 7 August 2012, C. Baldwin, A. Schrier, D. Pawson; USNM 431705, 57.0 mm SL, DNA #CUR14097, Curasub submersible, sta. 14-12, Curaçao, off Substation Curaçao downline, 12°05.00′N, 68°53.57′W, 174–297 m depth, 16 September 2014, C. Baldwin, L. Weigt, B. Van Bebber, R. Betancur.

Diagnosis. A species of Epigonus with the following combination of characters: dorsal-fin rays VI-I, 10; pectoral-fin rays 16–17; total gill rakers 25–27; vertebrae 10 + 15; pyloric caeca 6–7; pored lateral-line scales 32–35 + 3–5; opercular spine absent; maxillary mustache-like processes absent; ribs on last abdominal vertebra absent; lingual teeth present; endopterygoid teeth present; enlarged conical teeth on symphysis of lower jaw absent.

The DNA barcode for the holotype (USNM 422678) is as follows: NNNNNNNNNNNNNNNNNNNNNNNCCTCTATCTAGTATTTGGTGCTTGAGCTGGAATAGTAGGCACAGCCTTGAGTCTGCTTATTCGGGCAGAACTCAGCCAACCCGGCGCCCTCCTTGGAGACGACCAGATCTATAACGTAATTGTTACGGCGCATGCTTTCGTAATAATTTTCTTTATAGTAATACCAATCATAATTGGGGGTTTCGGAAATTGACTTATTCCCTTAATAATCGGGGCTCCTGATATGGCCTTCCCTCGTATAAACAACATAAGCTTTTGACTCCTCCCTCCTTCCTTTCTACTCCTCCTTGCCTCTTCTGGGGTAGAAGCAGGAGCCGGCACTGGGTGAACTGTCTACCCCCCTTTAGCTGGTAATCTCGCCCACGCGGGAGCCTCTGTTGACTTAACAATCTTTTCCCTACATTTAGCAGGTATTTCCTCAATTCTTGGGGCCATTAACTTCATTACAACAATTATTAACATAAAACCTCCTGCCATCTCTCAATATCAAACACCTTTATTTGTGTGGGCAGTCTTAATTACAGCAGTCCTTCTTCTACTTTCTCTCCCCGTACTTGCTGCTGGAATTACAATGCTCCTTACGGACCGAAATCTTAACACCACTTTCTTTGACCCAGCAGGGGGAGGGGATCCCATCCTTTATCAACACCTGTTTNNNNNNNNNN.

Description. Counts and proportional measurements are given in Table 1. Data for the holotype are presented first, followed by data of paratypes (if different) in parentheses. Body slender, laterally compressed, nape not humped, deepest at pectoral-fin base (Fig. 3). Head large, laterally compressed. Maxillary mustache-like process absent. Snout short and round; two nostrils close-set without dermal flap, anterior nostril short and with membranous tube, posterior nostril elliptical. Eye large, round, diameter subequal to postorbital length; bony rim of orbit slightly raised above dorsal profile; interorbital region concave at center. Mouth large, terminal, gape oblique; posterior margin of maxilla extending to below anterior margin of pupil; lower jaw not projecting when mouth closed; nob-like structures absent on symphysis of lower jaw. Upper jaw teeth minute, arranged in a single series, widely space. Lower jaw teeth minute, arranged in a single series, except two rows at symphysis of lower jaw, no enlarged teeth near symphysis. Vomerine teeth minute, small number of teeth scattered on anterior part and extending posteriorly along midline of palate. Palatine teeth minute, single row. Endopterygoids bearing single row of small conical teeth. Lingual teeth minute, arranged around outer edge of tongue and two rows near center, not forming dense tooth patch. Opercular spine absent; preopercle without spines, ventral and posterior margins smooth. Origin of first-dorsal fin located behind base of pelvic fin; first dorsal-fin spine long; third dorsal-fin spine the longest, length shorter than orbital diameter; two supernumerary spines on first dorsal pterygiophore. Spine of second dorsal fin long. First and second dorsal fins separated by gap longer than snout length. Origin of anal fin vertically below posterior portion of second dorsal-fin base; first anal-fin spine minute; second spine long, length shorter than orbital diameter; two supernumerary spines on first anal pterygiophore. Pectoral fin long, posterior tip of fin just reaching to vertical line from anus. Pelvic fin short, posterior tip not reaching to anus. Caudal fin deeply forked. Anus located vertically below origin of second dorsal-fin base. Ribs absent on last abdominal vertebra (Fig. 3c). Supraneural bones 3 (/0+0/0+1/1+1/1/). Scales deciduous, large, weakly ctenoid, covering the whole body except snout tip, anterior to rim of orbit, and surface of jaws; scales also present on bases of second dorsal, anal and caudal fins; series of pored lateral-line scales complete, 5 (3–5) pored scales on caudal fin. No trace of luminous organ around belly or pyloric caeca.

Color when fresh (Fig. 3b). Dorsal portion of body and head light gray; lower half of body silvery-white. Abdominal cavity semitransparent with inner black peritoneum. Pectoral, pelvic, and anal fins white. Dorsal and caudal fins light black.

Color in alcohol (Fig. 3a). Body and head uniformly light brown, except for abdominal cavity and gill cover which are beige. Pelvic fin white; pectoral, dorsal and caudal fins light brown, with many melanophores on the soft rays and membranes. Mouth cavity tan.

Distribution. Known only from Curaçao, southern Caribbean.

Habitat. Epigonids are common at Curaçao at depths near the lower limit of the Curasub (300 m), especially in caves and crevices along a near-vertical rock wall (Fig. 4; ESM Video S2). All specimens described in this study, including those of E. hexacanthus, were collected in this habitat.

Etymology. The specific name hexacanthus is derived from the Greek hexa-(six) and acanthus (spine) in reference to six spines on the first dorsal fin.

Comparison. Epigonus hexacanthus sp. nov. is unique in the genus in having six spines in the first dorsal-fin (vs. seven or eight spines in the first dorsal-fin; Okamoto and Gon 2018). Abramov (1987) described E. parini as having six spines in the first dorsal-fin, but Okamoto and Motomura (2013) noted that this species clearly has seven.

Epigonus hexacanthus sp. nov. belongs to the E. oligolepis group defined by Okamoto and Motomura (2011). The E. oligolepis group is distinguished from the other three species groups of the genus (the E. constanciae group, E. pandionis group, and E. telescopus group) in having 33–40 pored lateral-line scales (vs. 43–51 in the other three species groups: Okamoto and Motomura 2011; Okamoto and Gon 2018). Besides the present species, this species group comprises 6 species: Epigonus carbonarius Okamoto and Motomura 2011; Epigonus devaneyi Gon 1985; E. exodon; E. glossodontus; Epigonus indicus Idrees Babu and Akhilesh 2020; Epigonus oligolepis Mayer 1974. Epigonus hexacanthus sp. nov. can be distinguished from E. devaneyi and E. indicus by having lingual teeth (vs. absent; Okamoto and Motomura 2011; Idrees Babu and Akhilesh 2020). The present species also differs from E. carbonarius and E. oligolepis in having 25–27 gill rakers (vs. 21–23 in E. carbonarius and 29–32 in E. oligolepis). Epigonus hexacanthus sp. nov. differs from E. exodon and E. glossodontus by lacking enlarged conical teeth on the symphysis of lower jaw (vs. present; Gon 1985; Okamoto et al. 2020).

Remarks. Most species of Epigonus were described from adult specimens measuring 80–200 mm SL (Okamoto 2011, 2012, 2015; Okamoto and Motomura 2011, 2013; Okamoto and Gon 2018), and only Epigonus angustifrons Abramov and Manilo 1987 and Epigonus telescopus (Risso 1810) exceed 300 mm SL (Abramov 1992; Okamoto and Gon 2018). Ida et al. (2007) showed that E. cavaticus attains sexual maturity at the smallest size among the congeners, as females 63.7–66.8 mm SL had mature gonads. In this study, the holotype and seven paratypes of E. hexacanthus sp. nov. are females of 37.6–54.4 mm SL with a great number of eggs at several developmental stages. The most developed eggs were ca. 0.3 mm in diameter and were round with a single oil globule. Thus, E. hexacanthus sp. nov. seems to attain sexual maturity at the smallest size among the species.

The DNA barcode of the holotype, USNM 422678, clusters with 15 other sequences of E. hexacanthus from Curaçao in BOLD (USNM 413705, 413707, 413848, 413849, 413850, 413851, 413852, 413853, 413855, 413857, 413860, 426792, 413950, 413951, 433523). That lineage is approximately 11% divergent from E. gemma, 13% divergent from “Epigonus sp.” from India (GBMND26919-21, GBMND26920-21, and GBMND26921-21). From other species of Epigonus known from the Caribbean Sea that are represented in the BOLD database (E. denticulatus, E. macrops, E. pandionis), the barcode of E. hexacanthus differs by more than 19%. Intraspecific divergence in COI sequences for E. hexacanthus is < 1%.

Epigonus indicus Idrees Babu and Akhilesh 2020, which is in the same species group as E. hexacanthus sp. nov., was described as having 10 + 14 vertebrae, a count they considered as an important diagnostic character for the species. However, the radiograph in Idrees Babu and Akhilesh (2020, fig. 3) reveals a vertebral count of 10 + 15. Fishes of the genus Epigonus have total of 25 vertebrae, with abdominal and caudal vertebral counts of 10 + 15 or 11 + 14 (Mayer 1974; Okamoto and Gon 2018). Furthermore, Idrees Babu and Akhilesh (2020) suggested the presence of a ventral luminous organ based on a region of ventral fluorescent blue color in E. indicus. However, this is the peritoneum, not a ventral luminous organ. Among the species of the genus, only E. macrops has a ventral luminous organ, formed by a modification of one of eight pyloric caeca (Mayer 1974; Okamoto et al. 2012; Okamoto and Gon 2018).

Key to species of Epigonus of the Caribbean Sea

In the taxonomic study of Epigonus, Mayer (1974) reported six species from the Caribbean Sea: E. denticulatus; E. macrops; Epigonus occidentalis Goode and Bean 1896; E. oligolepis; Epigonus pectinifer Mayer 1974; and E. pandionis. Since then, Abramov (1992) and Gon (2003) have reported on the distribution of species of Epigonus in this area; however, no additional species have been found in the area. We provide a key to the species from the Caribbean Sea including the two species in this study.

  • 1a. First dorsal-fin spines 6 … E. hexacanthus

  • 1b. First dorsal-fin spines 7 … 2

  • 2a. Pored lateral-line scales 33–36 … E. oligolepis

  • 2b. Pored lateral-line scales more than 43 … 3

  • 3a. Opercular spine present … 4

  • 3b. Opercular spine absent … 5

  • 4a. Tooth patch present on tongue; maxillary mustache-like processes pointed; gill rakers 26–30 … E. pectinifer

  • 4b. Tongue toothless; maxillary mustache-like processes absent; gill rakers 24–26 … E. occidentalis

  • 5a. Gill rakers 18–20; ventral luminous organ present … E. macrops

  • 5b. Gill rakers 25–34; ventral luminous organ absent … 6

  • 6a. Enlarged teeth present on symphysis of lower jaw; pyloric caeca 8–9; ribs absent on last abdominal vertebra … E. gemma

  • 6b. Enlarged teeth absent on symphysis of lower jaw; pyloric caeca 10–14; ribs present on last abdominal vertebra … 7

  • 7a. Body moderately deep, body depth 22.4–29.6% SL; caudal-peduncle length 22.0–26.3% SL; gill rakers 26–30; 100–130 mm SL specimens with posterodorsally canted ring encircling the caudal peduncle (Mayer 1974; Okamoto and Motomura 2013) … E. pandionis

  • 7b. Body slender, body depth 15.8–23.6% SL; caudal-peduncle length 25.9–33.1% SL; gill rakers 28–34; 100–130 mm SL specimens without posterodorsally canted ring on caudal peduncle … E. denticulatus


Comparative materials. Epigonus denticulatus: AMS I.21669-005, 2 specimens, 124.0–132.3 mm SL, 33°31′S, 152°04′E, New South Wales, Australia, 28 September 1977; AMS I.29540-002, 125.3 mm SL, 35°32′S, 150°46′E, New South Wales, Australia, 10 August 1977. Epigonus exodon: NTUM 13370, 131.0 mm SL, 13°03′S, 45°01′E, south of Mayotte, western South Indian Ocean, 504 m depth, 27 January 2017. Epigonus carbonarius: holotype, MNHN 2010-983, 95.3 mm SL, female, 08°58′S, 140°04′W, off Nuku Hiva Island, Marquesas Islands, 391–408 m depth, 24 August 1997. Epigonus macrops: AMS I.22814-018, 131.6 mm SL, northwest of Port Headland, Western Australia, Indian Ocean, 704 m depth, 6 April 1982; AMS I.31161-004, 170.5 mm SL, off Cape Cuvier, Western Australia, Indian Ocean, 901 m depth, 28 January 1991. Epigonus occidentalis: UF 109570, 3 specimens, 69.8–88.2 mm SL, 24°14.1′N, 82°23.7′W, Florida Keys, 534 m depth, 8 June 1994; UF 113906, 2 specimens, 68.2–80.0 mm SL, 24°12.3′N, 82°37.5′W, Florida Keys, 559–577 m depth, 16 June 1998; UF 180268, 67.0 mm SL, 24°20.5′N, 83°14.5′W, Florida Keys, 144–157 m depth, 23 April 2003; UF 211404, 15 specimens, 60.3–92.9 mm SL, 14°23.0′N, 81°45.0′W, Caribbean Sea, 5 June 1962; UF 229213, 12 specimens, 61.2–187.5 mm SL, 14°35.0′N, 81°32.0′W, Caribbean Sea, 450–576 m depth, 31 January 1971. Epigonus oligolepis: UF 43252, 6 specimens, 104.5–150.3 mm SL, 26°11′N, 84°43′W, Gulf of Mexico, Florida, 300 m depth, 19 September 1985. Epigonus pandionis: UF 221291, 4 specimens, 136.7–182.0 mm SL, 03°45′N, 08°03′E, Equatorial Guinea, western Atlantic, 409–485 m depth, 14 May 1965; UF 221434, 19 specimens, 51.2–61.3 mm SL, 03°49′N, 07°38′E, Equatorial Guinea, western Atlantic, 264–269 m depth, 14 May 1965; UF 222947, 3 specimens, 162.9–180.0 mm SL, Caribbean Sea, 373–434 m depth, 14 July 1966. Epigonus pectinifer: HUMZ 190275, 67.1 mm SL, 08°10′3″S, 109°49′3″E–08°09′4″S, 109°48′8″E, off Java, Indonesia, 280–285 m depth, 13 September 2004.