Glandulotiron curvispinus, Just, 2022

Just, Jean, 2022, Tirons of the world: a review of ‘ tironid’ amphipods, description of new genera and species, and establishment of a new subfamily Tironinae Stebbing, 1906 stat. nov. (Crustacea, Synopiidae), Zootaxa 5139 (1), pp. 1-89 : 55-56

Glandulotiron curvispinus sp. nov.

( Figs 31–32 )

Type fixation. Holotype, sex not determined.—Here designated.

Etymology. This species is named for the large, recurved dorsal spine on urosomite 3.

Material. Holotype, sex not known, 4.2 mm, Australia, New South Wales, Jervis Bay, off Moona Creek, southeast of Huskisson , 35°03’S, 150°40’E, 8 m, fine sand with detritus and coarse shelly broadly rippled sand, just inside low rock reef covered with large brown algae, hand dredge, SCUBA, J. Just, P.B. Berents & R. T. Springthorpe, stn AU65, 15 November 1984. AM P105643 , (unique.)

Description. Head evenly curved dorsally, surface smooth rostrum broadly rounded, turned slightly forward; projecting interantennal lobes absent, lower corner of lateral head margin broadly rounded; eyes or single ommatidia not seen.

Mouthparts. Maxilla 1 palp apex with 3 short, serrate spine-seta and 1 pointed lateral spine-seta. Maxilliped outer plate with 2 spatulate spine-setae, inner plate with 2 similar spine-setae (not illustrated). Mouthparts otherwise appear normal.

Antenna 1 as long as pereonites 1–5.5 combined along dorsum, peduncle article 2 about 2/3 length of 1, article 3 about 5/6 length of article 2, article 1 with single penicillate seta ventrally and dorsally; flagellum as long as peduncle article 1 and half of article 2, of 4+ articles, accessory flagellum of 2+ articles, first article as long as peduncle article 3. Antenna 2 about 1.4 length of antenna 1, peduncular article 4 the longest, flagellum of 4+ articles, a few articles with single slender robust seta dorsodistally; antenna otherwise sparsely setose.

Coxal plates 1–4 distally with a single or two setae, without brim of fine setules.

Gnathopod 1 carpus 0.8 length of basis, with a few long setae on posterior margin; basis essentially naked; propodus about 0.5 length of carpus, with a single pectinate setae on midposterior margin; dactylus with unguis 0.6 length of propodus, moderately curved. Gnathopod 2 similar. Both gnathopods very sparsely setose except along posterior margin of carpus.

Pereopods 3–4 nearly naked, basis about as long as remaining articles combined; merus and propodus of equal length, carpus about 2/3 length of either with single robust seta in anterodistal corner.

Pereopod 5 basis broadest distally, posterior margin straight, posterodistal corner rounded rectangular. Pereopod 6 basis not widening distally, posterior margin straight, posterodistal corner broadly rounded rectangular, merus as long as carpus and propodus combined, carpus the shortest article. Pereopod 7 basis broadest in proximal half, tapering to weakly rounded posterodistal corner, ischium and merus combined as long as carpus and propodus together, propodus 2/3 length of carpus. All three pereopods sparsely setose with robust setae. Pereopods (5)6–7 propodus with 2 long robust setae in posterodistal corner; dactylus somewhat more oval then in other species of the genus.

Urosomite 3 dorsal spine long, pointed, recurved, with a few long setae; both spine and dorsal part of urosomite covered with small cuticle scales.

Uropod 1 rami of equal length, as long as peduncle, reaching to 1/2 along uropod 3 outer ramus. Uropod 2 peduncle reaching as far as uropod 1 peduncle, rami of subequal length, reaching 1/3 along uropod 3 outer ramus. Uropod 3 peduncle about 0.6 as long as outer ramus, rami reaching beyond apex of telson; outer ramus basal article with row of 4 robust setae dorsally, and 2 tiny robust setae ventrally, small second article with 3 dorsal robust setae; inner ramus reaching to 6/7 of basal article of outer ramus, dorsal margin with a single long plumose seta and 2 robust setae apically.

Telson. Length about 3.0 times greatest depth in lateral view, reaching 2/3 along outer ramus of uropod 3, with single robust seta and doublet of plumose setae dorsally on each lobe, apices with 1 long and 1 short robust seta.

Size. 4.2 mm.

Distribution. Australia, New South Wales, Jervis Bay, 8 m.

Remarks. The single specimen is damaged with soft-parts nearly completely dissolved. It differs from the other species of Glandulotiron by the somewhat forward pointing rounded rostrum, the lack of an interantennal projecting lobe, and an unusual forward curving dorsal spine on ursomite 3, but I tentatively refer it to Glandulotiron on account of the mouthparts (observed in situ only), coxal plates, and uropods with the distinctive second article on uropod 3 outer ramus.

Figures

FIGURE 31. Glandulotiron curvispinus gen. et sp. nov. Holotype. us, urosome. Habitus scale: 1 mm.

FIGURE 32. Glandulotiron curvispinus gen. et sp. nov. Holotype. gp1, gnathopod 1; p4–p7, pereopods 4–7.