Andamancalliax arafura, Poore, 2021

Poore, Gary, 2021, Indo-West Pacific and Australian species of Eucalliacidae with descriptions of four new species (Crustacea: Axiidea), Memoirs of Museum Victoria 80, pp. 1-41 : 2

Andamancalliax arafura sp. nov.

http://zoobank.org/urn:lsid:zoobank.org:act:1E5B7D96-E101-

45B8-AD22-7156C8B29B30

Figures 2 , 3

Material examined. Holotype. Australia, NT, Arafura Sea , 9.2055° S, 133.6483° E, 155–158 m, oozy mud ( RV Southern Surveyor stn 032 BS006 ), AM P.74526 (female, 3.7 mm, without major cheliped).

Description of holotype. Carapace smooth; gastric–abdominal regions together 4.3 times as long as width of these regions together; branchiostegite fully calcified; cervical groove at 0.62 carapace length, scarcely obvious on branchiostegite.

Rostrum acute, strongly tapering, two-thirds length of eyestalk. Anterolateral carapace lobe absent. Thoracic sternite 7 1.6 times as long as wide, with well-defined median sulcus over posterior half, smooth over medial half, weak lateral ridge anterior to coxal articulation crossing pit at quarter of width.

Pleonite 1 without anterior transverse groove, without sternal plates.

Eyestalk 1.8 times as long as greatest width, swollen laterally, tapering distally around cornea, with defined apical lobe; cornea wider than long. Antennular peduncle 1.8 times as long as width of both eyestalks; article 2 twice as long as wide; article 3 as long as article 2; article 3 with ventrolateral row of few setae, continued onto flagellum.Antennal peduncle 2.2 times as long as width of both eyestalks, overreaching antennule peduncle by most of article 5; scaphocerite ovoid, longer than wide; article 4 c. 5 times as long as wide; article 5 0.7 length of article 4. Maxilliped 3 basis with 4 mesial teeth along lower margin, ischium with strongly expanded proximo-lower lobe, tapering to two-thirds of its greatest proximal width; crista dentata of 3 short basal spines, plus 4 long sharp spines, first 2 recurved, last 2 overlapping merus; merus upper margin 1.5 times as long as greatest width; carpus–dactylus together reaching back to mid-ischium; dactylus as wide as long, with setose truncate apex; exopod third length of upper margin of ischium.

Major cheliped missing. Minor cheliped (right) ischium c. 2.8 times as long as distal width, lower margin with sharp subdistal spine; merus twice as long as broad, lower margin convex, unarmed; carpus 1.1 times as wide as upper length, margins carinate; propodus palm tapering, 0.9 times as wide as upper palm length, upper margin rounded, distomesial margin of palm oblique, distolateral margin of palm oblique, with triangular tooth at base of finger; fixed finger twice length of upper margin of palm, lateral cutting edge with proximal sharp oblique tooth, obtuse distal tooth; dactylus as long as fixed finger, 5 times as long as wide at base, cutting edge with obtuse rounded tooth at about two-thirds.

Pereopod 2 merus 2.2 times as long as maximum width; dactylus c. 5 times as long as upper margin of propodus. Pereopod 3 merus 2.3 times as long as maximum width; carpus 1.7 times as long as wide; propodus with lower margin concave, 1.3 times as long as mid-length; dactylus less than half as long as axial length of propodus. Pereopod 4 merus 3 times as long as maximum width; carpus 3 times as long as wide; propodus setose, with long distal spiniform seta among setose margin, as long as dactylus, with 2 long distal setae overlapping dactylus. Pereopod 5 chelate.

Pleopod 1 uniarticulate, tapering. Pleopod 2 endopod 2.6 times as long as wide; appendix interna at midpoint of endopod, reaching two-thirds remaining length of endopod. Pleopod 3 with appendix interna embedded in endopod.

Uropodal endopod ovoid, anterior margin more convex than posterior margin, widest at midpoint, 1.7 times as long as wide, without facial setae; exopod ovate, greatest dimension 1.6 times anterior margin, anterior margin straight, curving into distal margin, sharper curve between distal and posterior margins, with row of blade-like setae on distal posterior margin; dorsal plate defined by weak longitudinal ridge, extending half of exopod width, distal plate margin with a dozen scattered spiniform setae of various sizes. Telson 1.6 times as wide as long, broadest over anterior half, lateral margin evenly curving to posterior margin; posterior margin convex, with posterolateral clusters of long setae; dorsal surface smooth.

Etymology. For the Arafura Sea (noun in apposition).

Distribution. Australia, Arafura Sea. Shelf , 151– 158 m.

Remarks. The truncate setose dactylus of maxilliped 3, presence of a dorsal plate, spike-like rostrum and long fingers on the minor cheliped place the new species in Andamancalliax . The sole specimen differs from the illustrations of A. andamanica in the presence of a short exopod on maxilliped 3, a distal spine on the lower margin of the ischium of the minor cheliped, a tooth on the fixed finger of the minor cheliped, a more oval uropodal endopod and a less pronounced dorsal plate on the uropodal exopod. The few sharp spines that constitute the crista dentata are unique within Eucalliacidae ; the situation in A. andamanica was not reported. The dorsal plate of the uropodal exopod of A. arafura is less well developed than in A. andamanica , which was said to have the dorsal surface carinate and the anterior half elevated.

Figures

Figure 2. Andamancalliax arafura sp. nov. Holotype, Australia, NT, AM P.74526 (female, 3.7 mm): a, b, anterior carapace, eyestalks, antennule, antenna, pleonite 1, dorsal, lateral views; c, pleonite 6, telson, uropod (c’, detail of uropod exopod spiniform setae); d, thoracic sternite 7; e, f, minor cheliped (right), mesial, lateral views; g, pereopod 2; h, pereopod 3; i, j, pereopod 4, with detail of propodus, dactylus; k, pereopod 5. Scale bars = 1 mm.

Figure 3. Andamancalliax arafura sp. nov. Holotype, Australia, NT, AM P.74526 (female, 3.7 mm): a, b, left maxilliped 3, lateral, mesial views; c, left maxilliped 3, basis, merus, posterior view; d, pleonal sternite 1, pleopod 1; e, f, pleopods 2, 3. Scale bar = 1 mm.