Saccogaster horrida, Nielsen, Jørgen G., Schwarzhans, Werner & Cohen, Daniel M., 2012

Nielsen, Jørgen G., Schwarzhans, Werner & Cohen, Daniel M., 2012, Revision of Hastatobythites and Saccogaster (Teleostei, Bythitidae) with three new species and a new genus, Zootaxa 3579, pp. 1-36 : 12-14

Saccogaster horrida n. sp.

Figs. 7 , 8 , 25 , Tables 1 , 2, 4

Hastatobythites arafurensis (non Machida): Hoese & Gates 2006: 573.

Material examined (1 specimen, 59 mm SL). Holotype: NMV A 29718-019, female, 59 mm SL, off northwestern Australia, Leveque L27 transect, 14°51’12’’S, 121°25’53’’E to 14°50’43’’S, 121°27’01’’E, R/V Southern Surveyor, beam trawl, 403– 396 m, 2 July 2007.

Diagnosis. Saccogaster horrida differs from all other Saccogaster species by the following combination of characters: Distinct pair of free spines on frontal plate above and behind eyes, bony ridge above eye and cartilaginous ethmoidal spine in front of eyes; no scales, thin, transparent skin, no neuromasts; long gill rakers on anterior arch 2–3 times length of gill filaments; palatines with 2–3 tooth rows; pectoral peduncle twice as long as high; precaudal vertebrae 14 and total vertebrae 56; fin rays in dorsal 84, anal 57 and pectoral 21; otolith length to height = 1.75, otolith length to colliculum length = 2.1, sulcus with long pointed anterior projection.

Similarity. Saccogaster horrida seems most close to S. tuberculata , both lacking scales on the body. They differ from each other by S. horrida having a distinct frontal plate with a pair of well-developed spines (vs. no distinct plate and small sub-dermal spines), bony ridge above eye (vs. no bony ridge), vomer and premaxillaries with fangs (vs. no fangs), distance from base of pelvic fins to origin of anal fin 46% SL (vs. 32–39 % SL) and ratio otolith length to height = 1.75 (vs. 2.1–2.2).

Description. The principal meristic and morphometric characters shown in Table 4 . Head and body elongate and compressed with tapering caudal part and blunt snout. Scales absent. Lateral line not visible. Dorsal fin origin above middle pectoral fin and anal fin origin well behind midpoint of fish. Pectoral fin ending more than halfway to anus and with prolonged peduncle. Anterior gill arch ( Fig. 8 D) with six spiny knobs on upper branch, a developed raker in angle and lower branch with two developed rakers with a knob in between followed by 11 knobs. Developed rakers on anterior arch 2–3 times length of gill filaments. Pseudobranchial filaments not found. Ovaries well developed.

Axial skeleton (from radiographs): Number of precaudal vertebrae 14. Anterior neural spine one third length of second spine. Neural spines 2–4 long and depressed with pointed tips. Neural spines 5–14 shorter, with large basal parts and with pointed tips except for blunt in spines 6–9. Parapophyses developed on vertebrae 7–14. Pleural ribs on vertebrae 3–6 and epipleural ribs not seen.

Dentition: Palatines with 2–3 irregular rows of small, pointed teeth. Vomer boomerang-shaped and with 2–3 irregular tooth rows; inner row with ten large, pointed teeth and outer rows with small, pointed teeth. Premaxillaries with 3–5 irregular rows of granular teeth except for 2–3 fangs at symphysis. Dentaries with 3–4 irregular rows of small, pointed teeth except for larger teeth in inner row.

Head morphology ( Fig. 8 A–C): Head profile concave above eyes. Head with pair of free spines on frontal plate above and behind eyes, bony ridge above eye, frontal plate with rough-textured surface below skin, median, sub-dermal cartilaginous ethmoidal spine in front of eyes and median bony ridge (3 mm long) on dorsum behind frontal plate. Anterior nostril placed close to upper lip and small posterior nostril placed close to eye. Head pores: 1 supraorbital pore at tip of snout, 1 anterior infraorbital pore below and in front of eye, 1 anterior mandibular pore at tip of jaw. Head skin thin, tight. No neuromasts visible. Head with pigmentation patches around mouth and above eyes and opercular spine. Upper jaw ends well behind eye with posterior margin vertically expanded. Opercular spine pointed, almost reaching hind margin of operculum. No spine at lower angle of preoperculum.

Otolith ( Fig. 8 E–F): Otolith oval, moderately thick; otolith length to height = 1.75, otolith height to thickness = 1.9. Dorsal and ventral rims gently and regularly curved, smooth. Anterior and posterior tips regularly rounded resulting in a symmetrical outline of the otolith. Inner face slightly convex with centrally positioned, undivided oval, shallow sulcus with long and pointed anterior projection; otolith length to colliculum length = 2.1. Outer face convex.

Coloration: After five years of preservation body uniformly brownish. Head with scattered, small, black pigment mainly dorsally and on jaws. Frontal plate with a few larger, black pigment spots. Eyes blue with whitish lens.

Biology and distribution ( Fig. 25 ). A viviparous species caught on the upper continental slope at a depth of 396–403 m off northwestern Australia. Known from a female with ovaries containing many eggs but no embryos.

Etymology. The name “ horrida ” (meaning horrifying) refers to the spines and bony ridges above the eyes.

Figures

FIGURE 7. Saccogaster horrida, holotype, NMV A 29718 - 019, SL 59 mm, (photo M. Krag).

FIGURE 8. Saccogaster horrida, holotype: A—Lateral view of head. B—Lateral radiograph of head. C—Dorsal view of head. D—Anterior right gill arch. E—Median view of right otolith. F—Dorsal view of right otolith.

FIGURE 25. Geographic distribution of Hastatobythites and Saccogaster in the Indo-West Pacific. Each marking may represent more than one locality.