Epigonus exodon Okamoto & Motomura, 2012

Okamoto, Makoto & Gon, Ofer, 2018, A review of the deepwater cardinalfish genus Epigonus (Perciformes: Epigonidae) of the Western Indian Ocean, with description of two new species, Zootaxa 4382 (2), pp. 261-291 : 273-274

Epigonus exodon Okamoto & Motomura, 2012

(New English name: Buck-toothed Deepwater Cardinalfish) ( Figs. 1 , 10 ; Table 1, 2)

Epigonus exodon Okamoto & Motomura, 2012: 85 , fig. 1 (original description; type locality: Réunion, western South Indian Ocean , 21°03 S, 55°09 E, 450–480 m depth; holotype: MNHN 1991-0155 ).

Material examined. MNHN 1991-0155 , holotype, 97.0 mm SL, male, 21°03 S, 55°09 E, Réunion, western South Indian Ocean , 450–480 m depth, 8 September 1982 ; MNHN 2012-0134 , paratype, 60.2 mm SL, sex unknown, same data as holotype .

Diagnosis. Dorsal-fin rays VII-I, 10; pectoral-fin rays 16–17; total gill rakers 26–28; vertebrae 10 + 15; pyloric caeca 7; pored lateral-line scales 35–37 + 3; opercular spine absent; maxillary mustache-like processes absent; ribs on last abdominal vertebra absent; anteriorly projecting teeth present on each side of symphysis of lower jaw; tongue narrow; shallow V-shaped tooth patch present on rear two-thirds of tongue.

Measurements (% SL); counts are given in Table 1. Head length 33.4–34.2; head width 14.0–16.9; head height 16.4–17.3; body depth 23.9–24.6; body width 13.1–14.3; caudal-peduncle depth 8.8–9.6; caudal-peduncle length 28.0–28.9; orbital diameter 14.5–15.5; interorbital width 9.0–9.6; postorbital length 10.4–13.0; upper-jaw length 14.1–14.8; lower-jaw length 14.5–15.8; snout length 7.1–7.8; pre-first dorsal-fin length 34.7–36.2; presecond dorsal-fin length 55.3–56.6; pre-pectoral-fin length 34.7–36.0; pre-pelvic-fin length 38.2–41.8; pre-anus length 55.3–56.3; pre-anal-fin length 60.9–63.8; first spine length on first dorsal fin 2.7–3.2; second spine length on first dorsal fin 14.9–15.4; third spine length on first dorsal fin 16.0; second dorsal-fin spine length 13.3–14.1; first anal-fin spine length 1.8–2.3; second anal-fin spine length 12.5–13.3; pelvic-fin spine length 13.6–14.2; first dorsal-fin base length 11.5; second dorsal-fin base length 11.4–12.5; anal-fin base length 10.5–10.6; pectoral-fin length 20.2–20.4; pelvic-fin length 8.9–9.0.

Distribution. Réunion, western South Indian Ocean, at 450–480 m depth ( Okamoto & Motomura 2012) ( Fig. 1 ).

Comparisons and Remarks. Epigonus exodon belongs the E. oligolepis group, defined as having less than 40 pored lateral-line scales ( Fig. 10A ), lacking an opercular spine and ribs on the last abdominal vertebra. It can be easily distinguished from other congeners of the Western Indian Ocean by having 35–37 lateral-line scales and anteriorly projecting teeth on the symphysis of lower jaw (vs. more than 45 lateral-line scales and lacking projecting teeth on the symphysis of lower jaw in other congeners; E. bispinosus has two spines on the symphysis of lower jaw). Okamoto & Motomura (2012) reported an ontogenetic change in the anteriorly projecting teeth of the lower jaw (paratype, 60.2 mm SL, lacks the projecting teeth).

Figures

FIGURE 1. Distribution of four species of the Epigonus oligolepis group and the E. telescopus group in the Western Indian Ocean.

FIGURE 10. Epigonus exodon, MNHN 1991-0155, holotype, 97.0 mm SL. Overall body (A); and dorsal (B) and ventral (C) views of tipof the lower jaw, arrows show the anteriorly projecting teeth.