Pseudopleonexes justi sp. nov.

(Figs. 5–8)

Type material. Holotype: male, 6 mm, AM P62566, Point Lewis, Blanket Bay, Cape Otway, Victoria, Australia, 38°50’S 143°35’E, 26 April 1988, intertidal, on Caulocystis uvifera and Hormosira washings, P. B. Berents & R. T. Springthorpe. Paratype: female, 8 mm, AM P62567, type locality.

Diagnosis. Antenna 1 shorter than antenna 2. Antenna 2 slender, peduncle similar width to antenna 1 peduncle, not densely setose on ventral margin. Maxilla 1 palp with 2 articles. Gnathopod 1 carpus subequal in length to propodus, carpal lobe straight; propodus narrow; palm transverse, entire, without midmedial tooth, with posterodistal tooth defining palm, without defining robust seta; dactylus overreaching palm. Gnathopod 2 with long setae on margins, not plumose; basis posterodistal lobe large and rounded, with two to three slender setae; carpus longer than merus, shorter than propodus; propodus broad, ovoid, produced into an anterodistally setose lobe; palm acute, entire, without midmedial tooth, with small subacute posterodistal tooth defining palm, with one defining robust seta; dactylus subequal in length to palm. Pereopod 5 merus ovoid; distal articles broad. Pereopod 6 distal articles slender. Pereopod 7 distal articles slender. Uropod 3 peduncle with one distal robust seta.

Description. Based on holotype male, 6 mm, AM P62566. Head longer than deep. Epistome and upper lip angle directed posteriorly, at more than 45 degrees. Antenna 2 peduncular article 4 shorter than article 5; flagellum with 13 articles. Mandible molar well developed, triturating; with five robust setae in accessory setal row; palp with three articles, slender, short, apically setose, article 1 shorter than article 2 (0.81 x), article 2 shorter than article 3 (0.88 x), article 3 longer than article 1 (1.39 x). Upper lip distally setose, lateral margins each with a midlateral notch. Lower lip outer plate notched or entire, with medial and lateral lobes equal in size; mandibular lobe with curved margins, subacute apically. Maxilla 1 palp with 2 articles, with apical slender setae; inner plate with one slender seta. Maxilla 2 inner plate narrow, outer plate broader. Maxillliped outer plate with large robust setae.

Pereon. Coxae long. Gnathopod 1 smaller than gnathopod 2, without densely setose margins; coxa subequal to gnathopod 2 coxa, not produced distoventrally, distoventral margin rounded, ventral margin with a row of small setules and with a long tuft of slender setae in posteroventral corner; basis longer than coxa, with sparse, plumose or simple, slender setae, posterodistal lobe small and rounded, without setae; merus produced to form a small, rounded distoventral lobe, anterior margin without setae; carpus longer than merus, subtriangular, anterior margin without setae; propodus subrectangular; dactylus inner margin denticulate. Gnathopod 2 coxa ventral margin with a row of small setules; basis longer than coxa, with sparse slender setae; merus produced to form a short, subacute distoventral lobe, anterior margin without setae; carpus subtriangular, anterior margin with slender setae only; dactylus tapering evenly, acute, inner margin denticulate. Pereopod 3 basis expanded; merus anteriorly expanded. Pereopod 4 basis and merus similar to pereopod 3. Pereopods 5–7 weakly prehensile. Pereopod 5 basis without marginal robust setae, without medial slender setae; propodus slightly expanded distally, subrectangular, with three distal simple striated robust setae; dactylus slightly curved. Pereopod 6 basis posterior margin rounded proximally, straight distally, without marginal robust setae, without medial slender setae; merus subrectangular; propodus subrectangular, slightly expanded distally, with three distal simple striated robust setae; dactylus slightly curved. Pereopod 7 basis without marginal robust setae, without medial slender setae; propodus subrectangular, defined distally by one to two simple, striated robust setae.

Pleon. Epimeron 3 posteroventral corner broadly rounded. Uropod 1 short, reaching midlength of peduncle of uropod 2 (in situ); peduncle with three to five robust setae, with a short setal fringe, with distoventral spur absent; rami subequal in length; inner ramus with robust setae absent, with slender setae absent; outer ramus with three to five marginal robust setae, slender setae absent. Uropod 2 peduncle with a broad, rounded laterodistal projection, with more than five robust setae, setal fringe absent; inner ramus slightly shorter than outer ramus, marginal robust setae absent, slender setae absent; outer ramus with three to five marginal robust setae, slender setae absent. Uropod 3 peduncle longer than broad (1.49 x width). Long with respect to the rami length (2.77 x), marginal robust setae absent, marginal slender setae present, with more than five distal slender setae; rami broad; outer ramus subequal in length to inner ramus, with two large recurved distal robust setae; inner ramus with more than five distal slender setae. Telson subtriangular, with apical slender setae, denticles absent.

Female (sexually dimorphic characters). Based on paratype female, 8 mm, AM P62567. Antenna 1 longer than antenna 2; peduncular article 1 longer than article 2 (1.34 x), article 2 longer than article 3 (1.81 x), article 3 shorter than article 1 (0.41 x); primary flagellum with 17 articles; accessory flagellum absent. Antenna 2 flagellum with 12 articles. Gnathopod 1 subequal in size to gnathopod 2; basis subequal in length to coxa, posterodistal lobe absent; carpal lobe straight; palm defined by one robust seta. Gnathopod 2 without densely setose margins; basis shorter than coxa; propodus not produced anterodistally; palm transverse, without tooth defining palm; dactylus overreaching palm.

Etymology. This species is named after Dr Jean Just, who has contributed much to ampithoid systematics, especially to the genus Pseudopleonexes .

Remarks. Pseudopleonexes justi is different from the other species as follows: the gnathopod 1 coxa is subequal in size to gnathopod 2 coxa and the carpal lobe is straight; the gnathopod 2 merus is produced to form a subacute distoventral lobe and the propodus is produced anterodistally to form a setose lobe; pereopods 5–7 are weakly prehensile; the uropod 3 peduncle bears one distal robust seta; and the telson bears subapical setae.

Habitat. Pseudopleonexes justi sp. nov. occurs in the intertidal zone inhabiting several types of algae.

Distribution. Blanket Bay, Cape Otway, Victoria, Australia.