Gnathia cornuta Holdich and Harrison, 1980

Svavarsson, Jörundur & Bruce, Niel L., 2019, New gnathiid isopod crustaceans (Cymothoida) from Heron Island and Wistari Reef, southern Great Barrier Reef, Zootaxa 4609 (1), pp. 31-67 : 52-53

Gnathia cornuta Holdich and Harrison, 1980

( Fig. 18 A–E)

Gnathia cornuta Holdich & Harrison, 1980: 225 , fig. 4A–I. — Poore & Lew Ton, 2002: 188.

Material examined. ♂ (3.1 mm), Heron Island , ‘ Canyons’, reef slope, 23°28.389’S, 151°57.835’E, 8 December 1979, in dead coral, 7 m, coll. N.L. Bruce ( MTQ W10701) . 2 ♂ (3.1, 3.4 mm), Wistari Reef , off northern side of reef, 7 November 1978, in sediments, 22 m, coll. D. Fisk ( MTQ W10700) .

Remarks. This species is easily recognized on basis of the large paraocular tubercle, with its two V-shaped ridges and the internal lobe of the mandible ( Fig. 18E ) having a coarse crenulation. The mandibular lobe is short ( Fig. 18A, B ) in some specimens, while in larger specimens it reaches almost to the margin of the blade. Additional characteristic of the species is a fine crenulation laterally on the basal neck of the mandible ( Fig. 18B, C ).

This is the first report of the species from Heron Island. The species was previously only recorded from the Pallarenda, Townsville, Northern Queensland. Distribution. Northern Queensland (Townsville, Heron Island); from the intertidal to depths of 22 m.

Figures

FIGURE 18. Gnathia cornuta Holdich & Harrison, 1980. A–D, ♂, 3.1 mm (MTQ W10701); E, ♂, 3.4 mm (MTQ W10700). A, cephalosome, dorsal view. B, cephalosome, dorso-lateral view. C. cephalosome, lateral view. D. cephalosome, ventral view. E, mandible, mesial view. Scale for A = 0.05 mm.