Tiron lilljeborgi, 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 : 9-13

Tiron lilljeborgi sp. nov.

( Figs 2–3 )

Type fixation. Holotype, ♀.—Here designated.

Etymology. This species is named for Swedish zoologist Professor Wilhelm Lilljeborg who established the genus Tiron .

Material examined. Holotype, ♀, 7.5 mm. Australia, New South Wales, Twofold Bay off Eden, 37°03’50”S, 149°54’37”E, approximately 30 m, mud and fine wood chips, NSW State Fisheries , 2 May 1978, AM P27168. (Unique).

Description. Rostrum down curved, acutely pointed. Interantennal lobes triangular, bluntly rounded with row of marginal setae on apex. Eyes large oval, accessory eye of 2 separate ocelli.

Pleonites 1–3 with dorsoposterior double-spines and row of acute spines along posterior lateral margins.

Mouthparts. Maxilla 1 palp apex with 8 short, acute, finely deticulate setae; outer plate with 9 elongate, acute, strongly bifid spine-setae; inner plate with unbroken medial row of setae. Mouthparts otherwise normal.

Antenna 1 as long as pereonites 1–6 and half of 7 combined along dorsum, peduncle article 2 about 2/3 length of 1, article 3 3/4 length of article 2, article 1 with 1 plumose seta dorsally and 2 ventrolaterally; flagellum of 9 articles, article 1 with medioventral callynophore, articles 2 to 9 as long as peduncle, accessory flagellum of 4 articles. Antenna 2 as long as pereonites 1–7 and 1/3 of pleonite 1 combined along dorsum, peduncular article 4 twice as long as article 3, flagellum of 17+ articles, every second article from number 3 with a long slender robust seta dorsodistally, and often a shorter one ventrodistally; antenna otherwise sparsely furnished with small setae.

Coxal plates 1–3 of equal length, 4 slightly shorter and more tapering, all with dense row of long setae along distal margin; plate 6 posterior lobe larger than in 5.

Gnathopod 1 basis as long as merus and carpus combined, posterior margin with long setae proximally, with row of variously long setae in distal half of anterior margin; carpus broadest at proximal 1/3 point, anterior margin with a few setae only, posterior margin densely beset with long and short setae, lateral face with several setae in row, propodus half as long as carpus slender with 6 pairs of unequally long pectinate setae on posterior margin, dactylus with unguis half as long as propodus. Gnathopod 2 basis slightly longer than merus and carpus combined, posterior margin with row of long setae, anterior margin densely lined with long and short setae, carpus posterior margin rounded, deepest in middle with dense row of long and short setae, anterior margin with several setae, lateral face with a few setae in row, propodus slender, half as long as carpus, posterior margin with several groups of short and long setae, dactylus with unguis about half as long as propodus.

Pereopods 3–4 basis about 3.2 times longer than wide, as long as ischium, merus and carpus combined, with sparsely scattered small robust and simple setae of various length. Pereopods 5 and 6 basis ovoid, longer than wide, medially with row of a few short setae, carpus of pereopod 5 shorter than propodus, equal to propodus in pereopod 6, longer than propodus in pereopod 7. Pereopod 7 basis nearly circular, about as long as wide, medial surface with many scattered small setae, posterior margin smooth except micro-crenulation around distal curvature, entire posterior margin with numerous small setules.

Uropod 1 peduncle reaching as far as peduncle uropod 2, inner ramus the longer, reaching to middle of outer ramus uropod 3, lateral margin of peduncle with row of short robust setae, medial margin with several longer robust setae, rami with short (outer) and longer (inner) robust setae. Uropod 2 peduncle reaching to middle of uropod 3 peduncle, with row of lateral robust setae, inner ramus longer than outer, reaching as far as inner ramus of uropod 1, both rami with dorsolateral row of short robust setae. Uropod 3 peduncle about half as long as outer ramus, rami slender oval, outer ramus minutely longer than inner ramus, both reaching well beyond telson; both rami with dorsal row of long setae, outer ramus with dorsal row of 6 robust setae and ventrolateral row of 8 robust setae, inner ramus with dorsal row of 6 robust setae, midlateral row of small robust setae, and ventrolateral row of 5 robust setae.

Telson. Length about 6.6 times greatest depth in lateral view, reaching 2/3 along outer ramus of uropod 3, lobes with 2 small robust setae dorsally in distal half and a few simple setae.

Size. Largest ♂, 7.5 mm. ♀ not known.

Distribution. SE Australian shelf, approximately 30 m.

Figures

FIGURE 2. Tiron lilljeborgi sp. nov. Holotype, ♂. clv, head lateral view; clv & ant, head lateral view & antennae; gp1, gnathopod 1; gp2, gnathopod 2; mx1, maxilla 1; us, urosome, with dorsodistal margin of urosomite 3 enlarged.

FIGURE 3. Tiron lilljeborgi sp. nov. Holotype, ♂. cox 1–7, coxal plates 1 to 7; p3, pereopod 3 with apex enlarged (enl.); p4, pereopod 4; p5–7, pereopods 5 to 7; p7 med, medial view of pereopod 7 basis.