Paradexamine massa, Myers & LeCroy, 2009

Myers, Alan A., 2009, Dexaminidae *, Zootaxa 2260 (1), pp. 393-424 : 411-413

Paradexamine massa sp. nov.

( Figs 13 , 14 )

Type Material. Holotype, male, 2.5 mm, AM P78001, Picnic Beach , Palfrey Island (14 o 41.70'S 145 o 26.92'E), subtidal, protected beach, coral rock, rubble, sand patches, 0.3 m, S.E. LeCroy ( SEL /LZI-2-6) . Paratypes, 6 unsexed, AM P78002, same data as holotype .

Additional material examined. 5 females, AM P71106 ( QLD 1710 ) ; 1 male, AM P71047 ( QLD 1718 ) .

Type Locality. Palfrey Island , Lizard Island, Queensland, Australia (14°41.70'S 145°26.92'E) .

Etymology. From the Latin 'massa' = lump, referring to the swelling on the posterior margin of peduncle article 1 of antenna 1.

Description. Based on holotype, male, 2.5 mm, AM P78001.

Head. Head lateral lobes acute. Eye huge, more than half length of head, with black central core. Antenna 1 peduncle article 1 with medial rounded process on posterior margin. Antenna 2 length unknown; peduncle article 4 broader proximally, finely setulose; flagellum unknown. Mandible palp absent; incisor process lacking robust setal row. Maxilla 1 palp stout, about three times as long as broad. Labium mandibular lobes acute. Maxilliped palp 4-articulate.

Pereon. Gnathopod 1 carpus longer than 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 with single spine; dactylus much less 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 robust setae, posterodistal margin substraight, smooth. Pereopod 7 coxal gill present; basis moderately expanded, longer than broad, posterodistal margin serrated.

Pleon. Segments with the following dorsal spine arrangement (from urosomite 1 forwards): 1.3.3.0.0. Epimeron 2 posteroventral corner produced into a small 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 with many long fine setae. Telson lobes distally serrated, each lobe with multiple serrations of uneven size and shape, without distal spine, with subdistal robust seta, without subdistal slender seta.

Female (sexually dimorphic characters). Based on female, 2.4 mm, AM P71106. Eye large, about half or less length of head. Antenna 2 peduncle article 4 slender, parallel sided, weakly setulose. Uropod 3 rami lacking long fine setae.

Habitat. Soft bottom with sponges, corals, crinoids, hydroids, Halimeda .

Remarks. This species is close to P. pacifica ( Thomson, 1879) , but differs in the shape of the basis of pereopods 6 and 7. The posterodistal margin of the basis of pereopod 6 is almost straight and asetiferous in P. massa (weakly convex and evenly setose in P. pacifica ) and that of pereopod 7 is strongly serrate in P. massa (weakly serrate in P. pacifica ). In addition, the inner plate of maxilla 1 is asetiferous in P. massa (with two distal setae in P. pacifica ) and the mandibular processes of the labium are blunt in P. massa (finely pointed and recurved in P. pacifica ).

Distribution. Australia. Queensland: Palfrey Island and North Point, Lizard Island (current study).

Figures

FIGURE 13. Paradexamine massa sp. nov., holotype, male, 2.5 mm, AM P78001, Palfrey Island, Lizard Island, Great Barrier Reef.

FIGURE 14. Paradexamine massa sp. nov., holotype, male, 2.5 mm, AM P78001, Palfrey Island, Lizard Island; female, 2.4 mm, AM P71106, North Point, Lizard Island, Great Barrier Reef.