Tasmanida norfolkae, Ahyong, Shane T., 2007

Ahyong, Shane T., 2007, Decapod Crustacea collected by the NORFANZ Expedition: Galatheidae and Polychelidae, Zootaxa 1593, pp. 1-54 : 45-47

Tasmanida norfolkae sp. nov.

( Fig. 23 )

Type material. Holotype: NMNZ, female (8.2 mm), West Norfolk Ridge, 34°37.20’S, 168°57.03’E, 521–539 m, TAN0308/154 #25, 3 Jun 2003.

Description. Carapace: Transverse ridges well spaced, with short striae on hepatic region, with sparse plumose setae and few longer iridescent setae; cervical groove distinct; with pair of distinct, blunt epigastric spines behind supraocular spines; parahepatic and branchial regions with 12 or 13 small tubercles or blunt spines; with prominent, blunt postcervical spine and large, blunt, longitudinally carinate gastric spine. Frontal margins deeply concave, laterally weakly sinuous; rostral spine blunt, dorsally carinate, dorsally inclined, apex not exceeding eyes; supraocular spines slightly divergent, short, blunt, about one-quarter rostral length. Anterolateral spine stout, extending slightly beyond apices of supraocular spines. Margins of carapace anterior to cervical groove with 3 spines (including anterolateral; posterior 2 blunt); with 5 blunt spines posterior to cervical groove; posterior margin unarmed.

Sternum: Sternite 3 anteriorly biconcave; lateral margins rounded; posterior margin straight, fully contiguous with anterior margin of sternite 4. Sternite 4 trapezoid, smooth, without striae. Sternites 5–7 smooth. Ridges demarcating sternites smooth.

Abdomen: Tergite 2 with row of 4 blunt spines on anterior border and 2 short striae lateral to submedian spines; with 1 uninterrupted transverse stria; pleuron with 3 striae. Tergite 3 with row of 4 blunt spines on anterior border, each with lateral stria; with transverse striae, interrupted near level of outer anterior spine. Tergite 4 with row of 4 blunt spines on anterior border and median spine posteriorly; with transverse row of short striae behind anterior spines. Tergite 5 unarmed; with short, scattered striae.

Eye: Maximum corneal diameter 0.4 distance between apices of anterolateral spines; peduncle with long distal setae and a short setose stria.

Antennule: Basal segment elongate, slightly overreaching cornea; distomesial spine short; with 2 distolateral spines, dorsal subequal to distomesial spine, ventral minute; midlateral margin with 2 small spines.

Antenna: Distomesial spine of basal segment slender, reaching to level of apex of basal antennular segment. Segment 2 with distolateral and longer distomesial spine; distomesial spine not overreaching segment 3. Segment 3 with distomesial spine. Segment 4 with distolateral spine. Flagellum, short, as long as cheliped dactylus, reaching anteriorly to midlength of cheliped carpus.

Maxilliped 3: Ischium with strong distal flexor spine; extensor margin unarmed. Merus ovate, unarmed; length slightly exceeding twice height.

Pereopod 1 (cheliped): Slender, about 1.8 times carapace length; with short squamae; sparsely setose. Dactylus dorsal margin unarmed; occlusal margin finely denticulate, without gape. Propodus palm 1.9 times as long as high, longer than pollex; pollex margin unarmed. Carpus about 2 times as long as wide. Merus with short distal tooth on dorsal, ventral and mesial margins.

Pereopods 2–4: Similar, decreasing in length posteriorly; segments with sparsely distributed plumose and longer iridescent setae, primarily along extensor margin of merus. Merus with distal flexor spine; distal extensor margin with spine on pereopod 2, blunt on pereopods 3 and 4. Carpus with blunt, distal extensor and flexor projection; with few striae. Propodus 5.5–7.0 times as long as high; extensor margin unarmed, sparsely setose; flexor margin with 6 or 7 small movable spines. Dactylus 0.8–0.9 propodus length; flexor margin with 9 or 10 movable spines, distalmost spine proximal to base of unguis; terminal 0.2 of flexor margin unarmed.

Pereopod 5: Setal brush on propodal flexor surface extending from proximal third to distal third of pollex. Dactylus and proximal extensor surface of palm with plumose setae.

Etymology. Named norfolkae , derived from the type locality, the West Norfolk Ridge.

Remarks. Tasmanida norfolkae gen. et sp. nov. most closely approaches species of Neonida Baba & de Saint Laurent, 1996, Bathymunida Balss, 1914 , and Onconida Baba & de Saint Laurent, 1996, in sharing a slender rostral spine, deeply concave orbital margins, and a brush of setae on the flexor surface of the pereopod 5 propodus. Tasmanida differs from Bathymunida and Neonida in the following features: the distal mesial margin of the basal antennal segment is produced as a long spine that overreaches antennal segment 4, rather than a short, angular prominence or spine that does not reach the midlength of antennal segment 2; maxilliped 3 merus is unarmed and is about twice rather than one and a half times as long as high; and the cardiac region lacks a median prominence. Of the aforementioned taxa, T. norfolkae appears to be most similar to species of Onconida , particularly O. prostrata Baba & de Saint Laurent, 1996, sharing the unarmed cardiac region, the long mesiodistal spine on the basal antennal segment, short antennal flagellum, and ovate, unarmed maxilliped 3 merus. Tasmanida , however, is readily distinguished from Onconida by the following features: abdominal tergites 2 and 3 are spinose; the anterior margin of abdominal tergite 4 bears four instead of two spines; the distomesial spine of the basal antennal segment is much longer, reaching the apex rather than the midlength of the basal antennular segment; and the anteromedian margin of sternite 4, rather than being narrow, is broad and contiguous with the entire posterior margin of sternite 3. The presence of the dactylar spine on pereopod 5, a feature of male Onconida , remains to be determined for Tasmanida .

Baba & de Saint Laurent (1996) and Baba (2005) highlighted the taxonomic significance of the setation of the pereopod 5 chela, including the presence of a setal brush on the flexor face of the propodus in genera most similar to Tasmanida . Whereas Tasmanida also bears a setal brush on pereopod 5, that of Tasmanida is composed of simple rather than plumose setae (though setae on the dactyl and other parts of the propodus are plumose). Males of Neonida , Bathymunida , and Onconida lack pleopod 1. Male Tasmanida are presently unknown, but in view of the morphological features shared with Neonida , Bathymunida , and Onconida , males of the new genus are predicted also to lack pleopod 1.

The single known specimen of Tasmanida norfolkae was collected with Munida icela sp. nov., Munidopsis treis , and Agononida nielbrucei .

Distribution. Presently known only from the West Norfolk Ridge; 521– 539 m.

Figures

FIGURE 23. Tasmanida norfolkae gen. et sp. nov., female holotype, 8.2 mm, TAN 0308 / 154 (NMNZ). A, dorsal. B, carapace, right lateral view. C, left antennule and antenna, ventral view. D, distal portion of left basal antennular segment, lateral view. E, right third maxilliped, lateral view. F, sternum. G, telson. H, right cheliped, lateral view. I – K, right pereopods 2 – 4. L, right pereopod 5, chela. Scale: A, B, H – K = 2.0 mm; C – G, L = 1.0 mm.