Elaphognathia australis, N, Jörundur Svava R S S O & Bruce, Niel L., 2012

N, Jörundur Svava R S S O & Bruce, Niel L., 2012, New and little-known gnathiid isopod crustaceans (Cymothoida) from the northern Great Barrier Reef and the Coral Sea, Zootaxa 3380, pp. 1-33 : 3-7

Elaphognathia australis sp. nov.

( Figs 1–3 )

Material examined. Holotype. 3, 1.3 mm, Long Island, Chesterfield reefs, 19.8833°S, 158.31667°E, 4 May 1979, reef flat, exposed, 1 m, coll. N. L. Bruce (MTQ W10736).

Paratype. 3, 1.4 mm, cay, 6 km north of Long Island, Chesterfield reefs, c. 19.8833°S, 158.31667°19’E, 10 May 1979, lagoon, 300 m from reef crest, 1 m, in dead coral, coll. N. L. Bruce (MTQ W10728, + 9 microslides).

Description. Body 2.2 times as long as greatest width, widest at pereonite 3; dorsal surfaces smooth, without setae. Cephalosome semi-pentagonal, 0.6 as long as wide, lateral margins narrowing posteriorly; dorsal surface smooth; dorsal sulcus wide, shallow, short; translucent region absent; paraocular ornamentation absent, posteromedian tubercle present. Frontolateral processes present. Frontal margin concave, median point with process. External scissura absent. Mediofrontal process present, strong, acute, without ventral notch, without fine setae. Supraocular lobe pronounced, wide; accessory supraocular lobe not pronounced. Superior frontolateral process present, weak, rounded, with 1 long simple seta. Inferior frontolateral process absent. Mesioventral margin straight. Eyes present, round, 0.3 as long as cephalosome length, bulbous, standing out from head surface, ommatidia arranged in rows, eye colour faded, not known.

Pereon lateral margins subparallel, without setae; anteriorly smooth. Pereonite 1 fused dorsally with cephalosome; areae laterales absent on pereonite 5; pereonite 6 without lobi laterales; lobuii absent. Pleotelson 0.9 times as long as anterior width, lateral margins smooth, anterolateral margins weakly concave, posterolateral margin distally concave; mid-dorsal surface with 2 sub-median setae (set posteriorly), anterolateral margin without submarginal setae, posterolateral margin with 1 submarginal seta, apex with 2 setae.

Antennule peduncle article 3 1.8 times as long as article 2, 1.9 times as long as wide; flagellum 1.4 as long as article 3, with 4 articles. Antenna peduncle article 4 1.8 times as long as wide, 1.8 times as long as article 3, with 2 penicillate setae, and 3 simple setae; article 5 1.5 times as long as article 4, 2.7 times as long as wide, inferior margin with 8 simple setae; flagellum 1.0 as long as article 5, with 7 articles.

Mandibl e 0.5 as long as width of cephalosome, mandible rectangular, weakly curved, distally; mandible apex 10% total length; mandibular seta present. Carina present, smooth, along entire length. Incisor elevated, standing clear of surface, distal denticulation present. Blade present, dentate, with distinct angle, straight, along proximal 55% of margin. Pseudoblade absent; internal lobe present, bifid, large, smooth; dorsal lobe absent; basal neck short; erisma absent; lamina dentata absent.

Maxilliped 4-articled (articles 4 and 5 fused). Maxilliped article 1 lateral margin with distolateral mass of scale-setae; article 2 lateral margin with 3 plumose setae (PMS); article 3 lateral margin with 4 plumose setae; article 4 lateral margin with 11 plumose setae; endite extending to distal margin of article 2; without coupling setae. Pylopod article 1 1.3 as long as wide, without distolateral lobe; posterior and lateral margins forming rounded curve; lateral margin with 15 large PMS; mesial margin with continuous scale-setae, distal margin with 2 long simple setae; article 2 2.7 as long as wide; article 3 absent.

Pereopods 2–6 with long simple setae; propodus distal robust seta (RS) twice length of proximal RS; lateral and inferior margins with prominent tubercles, pereopod 2 with tubercles on merus and carpus. Pereopod 2 basis 2.4 times as long as greatest width, superior margin without long setae (and 2 penicillate setae), inferior margin with 6 setae (short); ischium 0.5 times as long as basis, 1.6 as long as wide, superior margin with 4 setae (short), inferior margin with 6 setae (short); merus 0.5 as long as ischium, 0.8 as long as wide, superior margin with 3 long setae (1 biserrate, 1 fine setulose), inferior margin with 4 long setae (1 fine setulose seta); carpus 0.6 as long as ischium, 2.1 as long as wide, superior margin without long setae, inferior margin with 2 setae (1 fine setulose seta); propodus 0.9 times as long as ischium, 2.6 times as long as wide, superior margin with 1 long seta (penicillate), inferior margin without short setae, without long simple setae, and with 2 RS; dactylus 0.7 as long as propodus. Pereopods 3 and 4 similar to pereopod 2. Pereopod 5 similar to pereopod 6. Pereopod 6 with tubercles on ischium to carpus, basis superior margin with 1 long seta, and no penicillate setae, inferior margin with 2 long setae; ischium 1.7 as long as greatest width, superior margin with 3 long setae, inferior margin with 2 long setae; merus 0.6 as long as ischium, 1.3 times as long as wide, superior margin with 3 long setae (2 biserrate), inferior margin 1 long seta (fine setulose seta), without dense patch of scale-setae; carpus 0.5 as long as ischium, 1.6 times as long as wide, superior margin with 1 long seta (penicillate), inferior margin with 3 long setae (and 1 fine setulose seta); propodus 0.8 as long as ischium, 2.8 times as long as wide, superior margin with 3 long setae, inferior margin without long setae, and 2 RS; dactylus 0.8 as long as propodus. Penes opening flush with surface of sternite 7.

Pleopod 2 exopod 2.1 as long as wide, 9 PMS; endopod 1.6 as long as wide, endopod with 8 PMS. Pleopod 2 appendix masculina absent.

Uropod rami extending beyond pleotelson, apices broadly rounded. Peduncle with 1 dorsal seta. Endopod 2.5 as long as greatest width, dorsally with 6 sensory setae; lateral margin sinuate, lateral margin with 1 simple seta; mesial margin weakly convex, with 6 long plumose setae. Exopod extending to end of endopod, 3.6 times as long as greatest width; lateral margin weakly convex, with 6 simple setae; proximomesial margin sinuate, proximally concave, mesiodistal margin with 4 long PMS.

Remarks. Elaphognathia australis sp. nov. is most similar to Elaphognathia forceps ( Holdich & Harrison, 1980) , but differs in the shape of the excavation of the frontal margin. In E. forceps the excavation is narrow and deep, while in E. australis the excavation is wide, with a wide rostrum-like medial frontal process.

Etymology. Alludes to the Southern Hemisphere locality of collection.

Distribution. Long Island, Chesterfield reefs, Coral Sea.

Figures

FIGURE 1. Elaphognathia australis sp. nov. A, 3, holotype, 1.3 mm (MTQ W 10736), B – E, 3 paratype, 1.4 mm (MTQ W 10728). B, cephalosome, dorsal view. C, cephalosome, dorso-lateral view. D, cephalosome, lateral view. E, cephalosome, ventral view. Scale = 0.5 mm.

FIGURE 2. Elaphognathia australis sp. nov., 3, paratype, 1.4 mm (MTQ W 10728). A, mandible, dorsal view, and antennule. B, mandible, ventral view, and antenna. C, maxilliped. D, pylopod.

FIGURE 3. Elaphognathia australis sp. nov., 3, paratype, 1.4 mm (MTQ W 10728). A, pereopod 2. B, propodus and dactylus of pereopod 2. C, pereopod 6. D, carpus and propodus of pereopod 6. E, pleopod 2. F, pleotelson and uropod.