Paradexamine saxeta, Myers & LeCroy, 2009

Myers, Alan A., 2009, Dexaminidae *, Zootaxa 2260 (1), pp. 393-424 : 418-420

Paradexamine saxeta sp. nov.

( Figs 19 , 20 )

Type Material. Holotype, female, 2.0 mm, AM P 70577, 200 m off Research Beach (14°40.83'S 145°26.75E), coarse biogenic sand with seagrass, 2.5 m, J. Just ( QLD 1626 ) . Paratype, 1 male, AM P78006, same data as holotype .

Additional material examined. 1 female, AM P70648 ( QLD 1634 ) ; 3 males, 1 female, 2 juveniles, AM P70704 ( QLD 1637 ) ; 1 female, AM P70935 ( QLD 1688 ) ; 1 male, 2 juveniles, AM P78007 ( QLD 1732 ) ; 1 male, AM P71099 ( QLD 1733 ) ; 1 female, AM P71259 ( QLD 1771 ) ; 1 male, AM P71330 ( QLD 1778 ) ; 3 females, AM P78009 ( SEL /LZI-2-3) ; 1 female, AM P78008 ( SEL /LZI-2-4) ; 2 females, AM P78010 ( SEL / LZI-5-2) .

Type Locality. Off Research Beach , Lizard Island, Queensland, Australia (14°40.83'S 145°26.75E'). Etymology. From the Latin 'saxetus' = a rocky place, referring to the Great Barrier Reef .

Description. Based on holotype, female, 2.0 mm, AM P70577.

Head. Head lateral lobes acute or subacute. Eye large, about half or less length of head, with black central core. Antenna 1 peduncle article 1 without process on posterior margin. Antenna 2 shorter than body length; peduncle article 4 slender, parallel sided, weakly setulose; flagellum with about 20 articles. Mandible palp absent; incisor process with robust setal row. Maxilla 1 palp elongate, more than four times as long as broad. Maxilliped palp 4-articulate.

Pereon. Gnathopod 1 carpus subequal in length with propodus; propodus not greatly expanded distally. Gnathopod 2 carpus elongate, slender, longer than propodus. Pereopods 3–7 simple or scarcely prehensile. Pereopod 3 coxa, posterodistal corner rounded; dactylus more than half length of propodus. Pereopods 5–7 of uniform morphology. Pereopod 5 basis subrectangular, with posterodistal lobe, anterior margin with short robust setae. Pereopod 6 basis pyriform, broadest proximally, posteroproximal margin convex, with few small robust setae, posterodistal margin concave, smooth. Pereopod 7 coxal gill present; basis slender or moderately expanded, much longer than broad, posterodistal margin, smooth or weakly serrated.

Pleon. Segments with the following dorsal spine arrangement (from urosomite 1 forwards): 1.3.0.0.0. Epimeron 2 posteroventral corner produced into a weak spine. Epimeron 3 posterior and ventral margins smooth, with a single strong posteroventral spine. Urosome with urosomites 2–3 fused. Urosomite 1 with dorsal spine only. Uropod 3 rami lacking long fine setae. Telson lobes distally serrated, each lobe with multiple serrations of uneven size and shape, without distal spine, without subdistal robust seta, with subdistal slender seta.

Male (sexually dimorphic characters). Based on paratype, male, 2.2 mm, AM P78006. Eye huge, more than half length of head. Antenna 2 length unknown; peduncle article 4 broader proximally, finely setulose; flagellum unknown. Uropod 3 rami with many long fine setae .

Habitat. Sand and rubble with coral patches.

Remarks. The poorly developed spines on the pleon of this material, together with its relatively small size, suggests it may be juvenile. However, it does not appear to be a juvenile of any of the other currently known GBR species and the male paratype has the enlarged eye, setose peduncle article 4 of antenna 2 and setose rami of uropod 3 that are characteristic of adult males. The strongly excavate posterodistal margin of the basis of pereopod 6 is not described for any other Australian species, although it occurs in a somewhat less exaggerated state in P. linga J.L. Barnard, 1972a . Paradexamine saxeta differs from P. linga in the more slender basis of pereopod 7 and in the much less acute lateral cephalic lobe. It also lacks robust setae on the ventral margin of epimeron 3. These are well-developed in P. linga .

Distribution. Australia. Queensland: Research Beach, Lizard Island (current study).

Figures

FIGURE 19. Paradexamine saxeta sp. nov., holotype, female, 2.0 mm, AM P70577, Research Beach, Lizard Island, Great Barrier Reef.

FIGURE 20. Paradexamine saxeta sp. nov., holotype, female, 2.0 mm, AM P70577, paratype, male, 2.2 mm, AM P78006, Research Beach, Lizard Island, Great Barrier Reef.