Platytyphlops petrescui Gerken 2018, n. sp.

Platytyphlops petrescui n. sp.

(Fig. 63–64)

Paralamprops serratocostatus.— Petrescu & Wittmann, 2003: 595.

Type material. Holotype: ovigerous female, GAM CUM 13931, 73°2.4’S, 28°28.1’W. Weddell Sea.

Other material. Subadult female, AM P66465, 33°2.6’S, 153°4.4’E, 3658 m.

Diagnosis. Carapace without lateral ridges, marginal carina anterior half weakly dentate, ridge absent on pseudorostrum; densely covered with blunt tubercles dorsal of the marginal carina; eyelobe without lenses or tumidities. Antennule article 1 not expanded; accessory flagellum 1.0 main flagellum. Pereopod 5 very short, but with proportions as in pereopods 3 and 4. Telson 1.0 uropod peduncles, with 3 terminal setae, terminal setae equal. Uropod endopod article 1 1.6 length of articles 2 and 3 together. Adult male unknown.

Description. Holotype ovigerous female, MGAB CUM 13931.

Ovigerous female, 12.6 mm. Carapace covered with club–shaped tubercles dorsal of marginal carina, posterior dorsolateral expansion, anterior crest with spines, with row of long setae parallel to anterior margin of carapace, all thoracic and pleonite segments with club shaped tubercles covering dorsal surface; pseudorostral lobes 0.32 carapace length; eyelobe 0.06 carapace length, no lenses; carapace 1.4 times length of all pereonites together (Fig. 63 A–B).

Antennule peduncle article 1 1.3 length article 2 and 3 together, with spines, 3 simple and 6 plumose setae; article 2 0.5 article 1 length, with 2 simple and 12 plumose setae; article 3 0.6 article 2 length, with 9 plumose setae; main flagellum of 6 articles, 0.75 peduncle length, with simple setae and 2 aesthetascs terminally; accessory flagellum equal to main flagellum, of 2 articles, with simple setae (Fig. 63C).

Antenna of 4 articles; article 1 with 2 pappose setae; article 2 with 1 pappose seta; article 3 margin serrate, unarmed; article 4 2.0 length of article 2 and 3 together, with 2 pedunculate and 1 simple setae terminally (Fig. 63D).

Mandible navicular, with 14 microserrate setae medially, lacinia mobilis with 3 cusps (Fig. 63E)

Maxillule with 2 endites; outer endite with 10 microserrate setae; inner endite with 2 simple, 1 microserrate and 1 dentate setae; palp with 2 setae (Fig. 63F).

Maxilla with 3 endites; broad endite distal margin with simple and pappose setae, medial margin with row of setae; medial narrow endite with 4 microserrate setae terminally; distal narrow endite with 5 microserrate setae terminally; both narrow endites extend past distal margin of broad endite (Fig. 63G).

Maxilliped 1 basis produced as broad lobe distally, lobe medial margin with 8 plumose setae, lateral margin of lobe with 4 pappose setae, distal margin with complex setae; ischium absent; merus with 1 plumose seta laterally; carpus 2.3 merus length, covered with pappose and comb setae, with 1 plumose seta laterally; propodus 0.5 carpus length, with pappose and simple setae; dactylus 0.6 propodus length, with 3 short simple setae terminally (Fig. 63H).

Maxilliped 2 basis with 9 plumose setae distally; ischium unarmed; merus 10.0 ischium length, with 2 simple setae medially and 1 plumose seta laterally; carpus 1.5 merus length, with 12 plumose setae medially and 1 plumose seta laterally; propodus 0.7 carpus length, with simple and plumose setae; dactylus 0.7 propodus length, with 3 simple setae terminally (Fig. 64A).

Maxilliped 3 basis longer than all other articles together, medial margin lined with plumose setae, lateral margin with fine hair like setae, with plumose setae distally, not expanded; ischium 0.02 basis, unarmed; merus 8.0 ischium length, plumose setae medially and laterally; carpus 2.1 merus length, with plumose setae medially and laterally; propodus 0.8 carpus length, with plumose setae medially and laterally; dactylus 0.5 propodus length, with simple setae; exopod as long as basis, basal article with 1 plumose seta, flagellum with plumo-annulate setae (Fig. 64B).

Pereopod 1 basis longer than next 4 articles together, medial margin lined with plumose setae, lateral margin with plumose setae; ischium 0.05 basis length, with 1 plumose seta; merus 4.0 ischium length, with plumose setae medially and laterally; carpus 1.6 merus length, with simple setae medially; propodus 0.8 carpus length, with simple setae; dactylus subequal to propodus, with simple setae; exopod shorter than basis, basal article with 8 plumose setae, flagellum with plumo-annulate setae (Fig. 64C).

Pereopod 2 basis as long as all other articles together, with plumose setae; ischium 0.04 basis length, with 1 microserrate seta; merus 3.5 ischium length, with 1 microserrate and 1 plumose setae; carpus 2.9 merus length, with 5 microserrate and 3 simple setae; propodus 0.25 carpus length, with 2 pedunculate and 2 simple setae; dactylus 3.2 propodus length, with simple setae; exopod shorter than basis, basal article with 5 plumose setae, flagellum with plumo-annulate setae (Fig. 64D).

Pereopod 3 basis 2.2 all other articles together, margin with 13 pappose setae; ischium 0.04 basis length, with 2 simple setae; merus 5.5 ischium length, with simple setae; carpus 0.5 merus length, with 2 simple and 2 annulate setae; propodus equal to carpus, with 1 annulate seta; dactylus 0.4 propodus length, with complex terminal seta (see detail in fig. 64F); exopod rudimentary, 0.09 basis length, of 2 articles, with simple setae (Fig. 64E).

Pereopod 4 basis 2.05 all other articles together, with plumose setae; ischium 0.04 basis length, with 1 plumose seta; merus 4.0 ischium length, with 2 simple and 3 annulate setae; carpus 0.6 merus length, with 2 annulate setae; propodus equal to carpus, with 1 annulate seta; dactylus 0.4 propodus length, with complex terminal seta (see detail); exopod rudimentary, 0.1 basis length, of 2 articles, with simple setae (Fig. 64F).

Pereopod 5 basis 1.4 other articles together, with 1 simple, 1 plumose and 1 pappose setae; ischium 0.07 basis length, with 1 plumose seta; merus 2.0 ischium length, with 2 simple setae; carpus 2.0 merus length, with 3 annulate setae; propodus 0.5 carpus length, with 1 annulate seta; dactylus 0.5 propodus length, with simple setae (Fig. 64G).

Telson 2.3 length of pleonite 6, with 6 microserrate with subterminal setule lateral setae, 3 microserrate with subterminal setule terminal setae (Fig. 64H).

Uropod peduncles 2.4 length of pleonite 6, equal to telson length, with 15 setae with single subterminal setule medially. Uropod endopod of 3 articles, 1.1 peduncle length; article 1 longer than 2 and 3 together, with 20–22 setae with single subterminal setule medially; article 2 0.3 article 1 length, with 5–7 setae with single subterminal setae medially, 1 pedunculate and 1 simple setae laterally; article 3 equal to article 2, with 3 setae with single subterminal setule medially, 1 pedunculate and 1 simple setae laterally, terminal seta with single subterminal setule, 0.7 article 3 length. Uropod exopod 0.9 length of endopod; article 1 0.2 length of article 2, with 2 simple setae; article 2 with simple setae on both margins, terminal seta 0.5 article 2 length (Fig. 64H).

Etymology. The species is named in honor of Iorgu Petrescu, in recognition of his extensive contributions to cumacean systematics.

Depth. 3658–3674 m

Distribution. Weddell Sea; Tasman Plain, off Australia.

Remarks. This species is similar to Platytyphlops echinatus and P. tuberculatus, in that the ornamentation of the carapace is dorsal to the marginal carina, and there are no other obvious ridges. Platytyphlops petrescui can easily be distinguished from P. tuberculatus by the antennule; in P. tuberculatus the first article of the antennule is greatly expanded, but in P. petrescui the first article is the same width as the second article. Platytyphlops petrescui can be distinguished from P. echinatus by the type and pattern of ornamentation, the setation of the antennule, and the proportions and armature of the telson. In P. echinatus the carapace and dorsal surfaces of the pereonites are covered in spines, the antennule peduncle has only two small setae, the accessory flagellum is shorter than the main flagellum, the telson is distinctly shorter than the uropod peduncles, and there are only two pairs of lateral setae on the telson; in comparison, in P. petrescui the dorsal surfaces of the carapace, pereonites and pleonites are covered in blunt tubercles, the antennule peduncle bears many long plumose setae, the flagella are equal in length, the telson is as long as the uropod peduncles, and the telson has six pairs of lateral setae.