Epigonus waltersensis Parin & Abramov, 1986

(New English name: Walters Shoals Deepwater Cardinalfish) (Figs. 3, 19; Tables 1, 2)

Epigonus waltersensis Parin & Abramov, 1986b: 182, fig. 4 (original description; type locality: 33°06 S, 44°04 E, Walters Shoals, Madagascar submarine ridge, 740–760 m depth; holotype: ZIN 47335); Abramov, 1992: 100 (key); Okamoto & Fukui, 2011: 391 (key); Okamoto, 2012: 252, fig.10n (photograph and key, based on original description).

Material examined. ZIN 47335, holotype, 129.0 mm SL, Walters Shoals, Madagascar submarine ridge, 33°06 S, 44°04 E, 740–760 m depth, 25 June 1979 (photograph and radiograph).

Diagnosis. Dorsal-fin rays VII-I, 9; pectoral-fin rays 17–18; total gill rakers 32; vertebrae 10 + 15; pyloric caeca 6; pored lateral-line scales 48; pungent opercular spine present; maxillary mustache-like processes absent; nub-like structures or spine on symphysis of lower jaw absent; ribs on last abdominal vertebra present; anus just below origin of second dorsal fin; tongue toothless; body depth 24.2% SL.

Measurements (% SL); counts are given in Table 1. Head length 35.9; head height 21.7; body depth 24.2; body width 14.1; caudal-peduncle depth 10.2; caudal-peduncle length 29.2; orbital diameter 15.0; interorbital width 8.9; postorbital length 15.0; upper-jaw length 15.1; lower-jaw length 14.7; snout length 7.8; pre-first dorsalfin length 38.8; pre-second dorsal-fin length 59.2; pre-pectoral-fin length 36.8; pre-pelvic-fin length 38.2; pre-analfin length 67.3; first spine length on first dorsal fin 1.6; second spine length on first dorsal fin 12.8; second dorsalfin spine length 12.8; second anal-fin spine length 11.4; pelvic-fin spine length 12.5; first dorsal-fin base length 11.4; second dorsal-fin base length 8.3; anal-fin base length 7.4; pectoral-fin length 16.7; pelvic-fin length 14.3.

Distribution. Walters Shoals, western South Indian Ocean (Parin & Abramov 1986b), at 740–760 m depth.

Comparisons and Remarks. Epigonus waltersensis is so far known only from the holotype collected on the Madagascar submarine ridge (Parin & Abramov 1986b). The specimen has eight anal-fin soft rays (Table 1), an unusual condition in Epigonus . Mayer (1974) noted this condition as a rare occurrence in several species of Epigonus and the holotype of this species could be such a case in E. waltersensis . Okamoto (2012) moved the species from the E. robustus species group (sensu Parin & Abramov 1986b) to the E. constanciae group. This species is similar to E. pectinifer in having 10 + 15 vertebrae, 9 soft rays on the second dorsal fin, and 6 pyloric caeca; however, it differs in having 32 gill rakers and lacking a maxillary mustache-like processes (vs. 26–30 total gill rakers and a sharp-pointed maxillary mustache-like processes present in E. pectinifer). Epigonus waltersensis can be distinguished from E. lenimen and E. robustus by having 10 + 15 vertebrae (vs. 11 + 14 in E. lenimen and E. robustus). Epigonus marimonticolus and two new species described in the present study, E. bispinosus and E. idai, differ from E. waltersensis in having 10 soft rays on the second dorsal fin (vs. 9 in E. waltersensis) and 10–15 pyloric caeca (vs. 6 in E. waltersensis). Furthermore, E. waltersensis can be distinguished from the remaining 7 species of the genus in the Western Indian Ocean by having a pungent opercular spine (Fig. 19).