Platytyphlops echinatus Gerken 2018, n. sp.

Platytyphlops echinatus n. sp.

(Figs 56–58)

Type material. Holotype: subadult female AM P101490, 33°40’S, 152°6’E, 1115 m, off Sydney, Australia, 19 December 1985. Paratypes: subadult female AM P101491, subadult female AM P101492, subadult male AM P101500, collected with holotype.

Diagnosis. Carapace without lateral ridges, covered in spines dorsal of marginal carina, marginal carina dentate, ridge absent on pseudorostrum; eyelobe without lenses or tumidities. Antennule article 1 not expanded; accessory flagellum 0.6 main flagellum. Telson shorter than uropod peduncles, with 3 terminal setae, terminal setae equal. Uropod endopod broken. Adult male unknown.

Description. Holotype subadult female, AM P 101490.

Subadult female, 14.0 mm. Carapace covered with spines dorsal to marginal carina, no spines ventral of carina, posterior dorsolateral expansion, with anterodorsal ridge; pseudorostral lobes 0.3 carapace length; eyelobe 0.07 carapace length, no lenses; carapace 2.5 length of pereonites; pereonites with spines dorsally (Fig. 56 A–B).

Paratype subadult female, AM P 101491.

Antennule peduncle article 1 longer than articles 2 and 3 together, margins with spines, unarmed; article 2 1.1 article 3 length, margin with 2 spines, 1 simple seta; article 3 with 4 simple setae; main flagellum of 5 articles, subequal to peduncle, with simple setae and 2 aesthetascs terminally; accessory flagellum of 3 articles, extending to anterior border of main flagellum article 3, with simple and plumose setae (Fig. 56C).

Antenna of 4 articles; article 1 with 2 spines on margin, 2 pappose setae; article 2 with 1 pappose seta; article 3 with 1 spine and 1 pappose seta; article 4 longer than articles 1–3 together, terminal seta broken (Fig. 56D).

Mandible navicular, with 16 setae medially (Fig. 56E).

Maxillule with 2 endites; outer endite with 9 stout setae; inner endite with 2 microserrate and 2 simple setae; palp with 2 setae (Fig. 56F).

Maxilla with 3 endites; broad endite distal margin with pappose, simple, and microserrate setae, medial margin with row of 33 setae; medial narrow endite with 4 microserrate setae terminally; distal narrow endite with 5 microserrate setae terminally; both narrow endites extend just past distal margin of broad endite (Fig. 56G).

Maxilliped 1 basis produced distally as broad lobe, distal margin with 2 stout setae, lobe margins with 2 pappose setae and row of 10 simple setae; ischium absent; merus with 1 pappose seta laterally; carpus medial face with simple and comb setae, 1 pappose seta laterally; propodus with simple and plumose setae distally; dactylus with 3 simple setae terminally (Fig. 56H).

Paratype subadult female, AM P 101491.

Maxilliped 2 basis as long as next 4 articles together, medial margin with 3 pappose setae, distal corner with 3 pappose setae; ischium unarmed; merus 2.0 length of ischium, with 1 pappose seta medially, 1 pappose seta distally; carpus 1.5 merus length, with plumose and simple setae medially, 1 plumose seta distally; propodus 0.8 carpus length, with plumose and simple setae; dactylus 0.7 propodus length, with 2 simple setae (Fig. 56I).

Maxilliped 3 to pereopod 2 broken, not illustrated.

Pereopod 3 basis 2.2 all other articles together, with 8 plumose setae; ischium 0.05 basis length, with 1 simple seta; merus 5.3 length of ischium, with 1 simple seta; carpus 0.4 merus length, with 1 simple and 2 annulate setae; propodus 0.7 carpus length, with 1 annulate seta; dactylus 0.6 propodus length, with 1 simple seta; exopod rudimentary, 0.08 basis length, 2 articles, with simple setae (Fig. 4A).

Pereopod 4 broken, not illustrated.

Paratype subadult female, AM P 101491.

Pereopod 5 basis 1.4 all other articles together, unarmed; ischium 0.1 basis, unarmed; merus 1.2 ischium, unarmed; carpus 1.2 merus, unarmed; propodus 1.2 carpus, unarmed; dactylus 0.4 propodus, with 5 simple setae (Fig. 57B).

Paratype subadult female, AM P 101492.

Telson 1.3 length of pleonite 6, with 2 lateral simple setae, 3 terminal simple setae, shorter than terminal setae (Fig. 57C)

Uropod peduncles 2.0 length of pleonite 6, with 12–15 medial setae with single subterminal setule (Fig. 57C). Uropod rami broken.

Paratype subadult male, AM P 101500.

Antennule peduncle article 1 1.1 length of article 2 and 3 together, with spines and 9 plumose setae; article 2 0.6 article 1 length, with 13 plumose setae; article 3 0.6 article 2 length, with 6 simple and 4 plumose setae; main flagellum of 6 articles, longer than peduncle, with simple setae, 2 aesthetascs terminally, first article expanded, suggesting adult male will have group of setae on the first article; accessory flagellum of 3 articles, extending to anterior border of main flagellum article 4, with simple setae (Fig. 57D).

Antenna peduncle of 5 articles, flagellum with many short articles, no setae present (Fig. 57E).

Maxilliped 3 basis 0.8 all other articles together, medial margin serrate distally with 11 pappose setae, not expanded distally, with 2 plumose setae at distal corner; ischium 0.08 basis length, with 1 plumose seta; merus 2.4 ischium length, medial margin serrate with 2 plumose setae, 3 plumose setae distally; carpus 2.5 merus length, with 8 medial plumose setae, 4 plumose setae laterally; propodus 0.7 carpus length, with 9 plumose setae medially, 5 plumose setae laterally; dactylus 0.5 propodus length, with 3 simple setae terminally; exopod as long as basis, basal article with 2 plumose setae, flagellum with plumo-annulate setae (Fig. 57F).

Pereopod 1 broken, not illustrated.

Pereopod 2 basis equal to next 4 articles together, with 5 plumose setae; ischium 0.06 basis length, with 3 plumose setae; merus 2.6 ischium length, with 2 simple and 1 microserrate setae; carpus 3.4 merus length, with 11 microserrate setae, 1 simple seta; propodus 0.2 carpus length, unarmed; dactylus 4.0 length of propodus, with 12 simple setae; exopod shorter than basis, basal article with 4 plumose setae, flagellum with plumo-annulate setae (Fig. 57G).

Pereopod 3 basis 1.6 all other articles together, margin partially serrate, with 4 plumose setae; ischium 0.07 basis length, with 1 simple and 2 plumose setae; merus 4.5 ischium length, unarmed; carpus 0.3 merus length, with 2 simple and 2 annulate setae; propodus 0.8 carpus length, with 1 annulate seta; dactylus 0.6 propodus length, with 2 simple setae terminally; exopod shorter than basis, basal article with 2 plumose setae, flagellum with plumoannulate setae (Fig. 58A).

Pereopod 4 broken, not illustrated.

Pereopod 5 basis 1.5 all other articles together, with 1 pedunculate and 3 simple setae; ischium 0.1 basis length, with 1 simple seta; merus 1.2 ischium length, with 1 simple seta; carpus 1.6 merus length, unarmed; propodus equal to carpus, with 1 simple seta; dactylus 0.25 propodus length, with 3 simple setae terminally (Fig. 58B).

Pleopod 1 (Fig. 58C).

Telson 1.3 length of pleonite 6, with 2 lateral setae with single subterminal setule, 3 terminal setae (Fig. 58D)

Uropod peduncles 2.3 length of pleonite 6, with 15 medial setae with single subterminal setule. Uropod rami broken, exopod article 1 distinctly much less than 0.5 article 2 length (Fig. 58D).

Etymology. The species is named echinatus, in reference to the spine covered carapace and pereonites.

Depth. 1115 m.

Distribution. 33°40’S, 152°6’E.

Remarks. Platytyphlops echinatus is most similar to P. bamberi, P. petrescui and P. tuberculatus. Platytyphlops bamberi is easily distinguished by the presence of spines on the carapace ventral of the marginal carina, and unequal terminal setae of the telson; in P. echinatus there are no spines on the carapace ventral of the marginal carina, and the telson terminal setae are subequal in length. Platytyphlops tuberculatus is easily distinguished by the expanded article 1 of the antennule; in P. echinatus article 1 of the antennule is the same width as article 2. Platytyphlops petrescui can be distinguished by the carapace, pleonites and pereonites covered with blunt tubercles, setose antennule, equal flagella of the antennule, telson equal to the uropod peduncles, and six pairs of lateral setae on the telson; in comparison, in P. echinatus the dorsal surfaces of the carapace and pereonites are covered with sharp spines, the antennule has only two setae, the accessory flagellum is distinctly shorter than the main flagellum, the telson is shorter than the uropod peduncles, and there are only two pairs of lateral setae on the telson.