Pereionotus thomsoni Stebbing, 1899

Coleman, Charles Oliver, 2009, Phliantidae *, Zootaxa 2260 (1), pp. 766-770 : 766-767

Pereionotus thomsoni Stebbing, 1899

( Figs 1 , 2 , Pl. 5C)

Pereionotus thomsoni Stebbing, 1899: 417 , pl. 35A. ― Barnard & Karaman, 1991: 587. ― Lowry & Stoddart, 2003: 222 (catalogue).

(?) Pallinotus thomsoni japonicus Hirayama, 1987: 35 , pl. 245–246.

Palinnotus thomsoni . ―J.L. Barnard, 1972: 295, pl. 176–179.

Material examined. Male, 2.6 mm, AM P71365 ( QLD 1820). Female, AM P78903 ( SEL /LZI-2-3).

Type locality. Watsons Bay , New South Wales, Australia (~ 33º51'S 151º17'E) .

Description. Based on male, 2.6 mm, AM P71365.

Head and body. Body depressed, dorsal keel, coxal plates splayed. Cuticle with pits and microtrichs. Pereonite 1 with 2 dorsal shallow carinae, pereonites 2-6 and pleonites 1-2 with hump-like shallow carinae. Head with protruding eyes and short rostrum. Antenna 1 peduncular article 1 dorsolaterally expanded into subacute tooth; article 2 with a shorter pointed tooth; flagellum consisting of only one article with long aesthetascs apically. Antenna 2 with apical bundle of aesthetascs on second flagellar article; slender, reaching middle of article 2 of antenna 1 in lateral view. Mandible without palp, incisor multidentate, molar spine-like. Lower lip with wide lobes. Maxilla 1 inner plate simple; palp short, uniarticulate. Maxilla 2 inner and outer plates basally fused. Maxillipeds inner plate subrectangular with 3 nodulose setae apically; outer plate longer than palp; palp 3-articulate.

Pereon. Coxae 1–4 with distal row of biserrate setae. Gnathopod 1 coxa anterior margin slightly excavate; basis shorter than coxa; ischium longer than merus; carpus slightly expanded distally; propodus medial face with transverse row of stout plumose setae and posterodistal robust setae; dactylus falcate, with simple seta on inner curvature. Gnathopod 2 similar to gnathopod 1, but coxa with anterior margin straight and row of medial propodus setae not developed. Pereopod 3 coxa wider than that of gnathopod 2, basis and ischium similar, but merus and to a lesser extent the carpus drawn out into an anteromarginal rounded lobe; propodus and dactylus as for gnathopod 2. Pereopod 4 coxa with posteromarginal subacute lobe; basis to dactylus as for pereopod 3. Pereopods 5 and 6 coxa bilobed, more than 2x longer than deep; basis expanded into rounded posterior lobe; ischium long; merus with posterodistal rounded lobe; carpus short, subrectangular; propodus and dactylus as in preceding appendages. Pereopod 7 basis posteroproximal margin rounded, constricted and quadrate distally; ischium to dactylus similar to preceding appendages, except for a more extended merus lobe.

Pleon. Urosomite 1 longest. Uropod 1 outer ramus slightly shorter than inner, both rami with one short rounded robust seta apically. Uropod 2 peduncle very short, inner ramus surpasses outer ramus, both rami with one terminal rounded robust seta. Uropod 3 hidden below telson, rami lacking. Telson wider than long, subtriangular with rounded apex.

Female (sexually dimorphic characters). Based on female, AM P78903. Wider body. Processes on peduncular articles 1–2 of antenna weakly developed.

Habitat. Found in between sponges.

Remarks. The description agrees well with that of J.L. Barnard (1972) who discussed the differences of his specimen from the west coast of Australia from Stebbing´s (1899) original description. The only deviations from Barnard´s description concern antenna 2, which appears longer in relation to antenna 1, and the telson, which is shorter in the material studied herein compared to Barnard´s and Stebbing´s illustrations. Hirayama (1987) described the subspecies P. t. japonicus , however, due to many differences to the Australian material, it seems very probable that it is a separate species.

Distribution. Australia. Queensland: Lizard Island (current study); New South Wales: Watsons Bay ( Stebbing 1899); Western Australia: Cheyne Beach (J.L. Barnard 1972).

Figures

FIGURE 1. Pereionotus thomsoni Stebbing, 1899, male, 2.6 mm, AM P71365, Lizard Island, Great Barrier Reef.

FIGURE 2. Pereionotus thomsoni Stebbing, 1899, male, 2.6 mm, AM P71365, Lizard Island, Great Barrier Reef.