Australian Dragonfish

Eustomias australensis

DIAGNOSIS.—Two terminal bulbs separated by a distance equal to the distal-bulb length, 1.8% SL). Barbel 55% SL. Terminal filament longer than 9.4% SL, the tip broken. Distal bulb large, 1.8% SL, 1.6 times length of proximal bulb. Axis of stem pigmented, dark proximally, light distally. External chevron-shaped or roundish striated areas on stem well pigmented. Middorsal paired spots between occiput and dorsal-fin origin 8.

DESCRIPTION OF HOLOTYPE.—Sex not determined, 87.0 mm SL. D 23. A 36. P1 3. P2 7. IP 7. PV 34. VAV 18. OV 34. VAL 20. AC 18. IA 59. IC 77. OA 54. OC 72. VAV photophores over anal-fin base 7. Branchiostegal photophores damaged. Premaxillary teeth 10 left, 9 right: from anterior to posterior, a long fixed tooth followed by a long space, a fixed fang followed by a moderate space, a short-to-long series of 1 fixed and 2 depressible teeth (middle, depressible tooth not present right) followed by a moderate space, a short fixed tooth followed by a moderate space, 2 intermediate-sized depressible teeth followed by a moderate space, and 2 short depressible teeth. Maxilla with about 10 short, slanted serra-like teeth. Mandibular teeth 15 on both sides: from anterior to posterior, a short, fixed symphysial tooth followed by a moderate space, a fixed fang followed by a long space, a long depressible tooth, a short-to-long series of 1 fixed and 3 depressible teeth (1 and 4 on right), a short-to-long series of 5 depressible teeth (1 fixed, 3 depressible right), and a short-to-long series of 3 depressible teeth. Vertebrae approximately 67 (not X-ray dense).

Measurements (in mm): Predorsal length 73.8, preanal length 64.0, prepelvic length 52.1, head length ~10.9, barbel length 48.1, proximal-bulb length 1.0, distal-bulb length 1.6, distance between bulbs 1.6, fleshy orbit length ~1.8, postorbital-organ length 0.4, upper-jaw length 8.4, depth behind head 3.8, greatest depth 4.5, caudal-peduncle depth 1.5, pectoral fin damaged, pelvic-fin length ~11.5, dorsal-base length 10.6, anal-base length 21.6, longest premaxillary tooth 1.1, longest mandibular tooth 1.0.

Barbel stem with axis moderately darkly pigmented proximally, becoming light distally. External chevron-shaped or roundish striated areas darkly pigmented, large and closely spaced proximally, smaller and more widely spaced before bulb. Axis between bulbs unpigmented proximally, moderately dark distally. No visible pigment in filament. Proximal bulb spheroidal; distal bulb more or less ovoid, narrower distally, about 1.5 times as wide as proximal bulb.

SIMILAR SPECIES.—Eustomias bituberatus and bituberoides have a similarly intermediate interspace between the bulbs; in all other species with relatively simple terminal filaments the interspace is either longer (Atlantic species) or shorter (Pacific species). Both bituberatus and bituberoides have longer barbels than australensis, and bituberoides has a smaller distal bulb (Figures 6 and 7).

DISTRIBUTION.—Known only from the holotype, taken in the Tasman Sea off southeastern Australia (Figure 40).

ETYMOLOGY.—An adjective derived from the name of the continent of Australia plus the Latin suffix -ensis (denoting locality of occurrence), alluding to the place of capture of the only known specimen.

MATERIAL EXAMINED (1 unsexed).—Holotype: AMS i.20901-001 (?, 87), 36°37′S, 152° 10′E, 0–500 m, 1959–2215, 20 Jan 1978.