Crosnierita adela, Ahyong, Shane T., Taylor, Joanne & Mccallum, Anna W., 2013

Ahyong, Shane T., Taylor, Joanne & Mccallum, Anna W., 2013, New species and new records of deepwater munidid squat lobsters from north-western Australia: Onconida, Bathymunida, Crosnierita, Plesionida and Torbenella, Zootaxa 3734 (1), pp. 23-37 : 27-29

Crosnierita adela sp. nov.

( Fig. 2 )

Material examined. HOLOTYPE: NMV J56116 , male (cl 12.7 mm, pcl 9.0 mm), Barrow L1 transect, 21°00.816– 00.780'S, 114°39.150–38.898'E, 258–271 m, Sherman sled, SS05/2007/011 (acq. 008), 10 Jun 2007.

Description of holotype. Carapace: Slightly wider than long (width 1.2 pcl). Rostral spine broken but apex exceeding eyes, with low dorsal carina; supraocular spines parallel, well developed, length about half rostral length. Surface with transverse ridges well spaced, with short granular scale-like striae on hepatic and anterior branchial regions, striae minutely setose; cervical groove distinct. Pair of distinct, blunt epigastric spines behind supraocular spines; blunt postcervical spine and large, laterally compressed gastric process, apex broken. Cardiac region with prominent dorsal process, apices broken but indicating 2 spines or processes. Upper orbital margins deeply concave, laterally sinuous; lower orbital margins visible dorsally, mesially with spatulate, distally acute process. Anterolateral spine stout, broad, lateral margins convex, apex extending to level of apices of supraocular spines. Margins of carapace anterior to cervical groove with spine (excluding anterolateral); 4 spines posterior to cervical groove; posterior ridge with small median spine.

Sternum: Sternite 3 anteriorly sinuous; shallow median notch; laterally rounded; posterior margin arcuate, medially contiguous with anterior margin of sternite 4. Sternite 4 trapezoid, smooth, with few scattered striae. Sternites 5–7 smooth, without striae. Ridges demarcating sternites smooth.

Abdomen: Tergites 2–3 with row of 4 blunt spines on anterior border, lateral spines shorter than submedian spines, apices damaged in holotype; straight stria lateral to submedian spines; posteriorly with uninterrupted transverse stria and indistinct interrupted stria; pleuron with 2 main striae and several short striae. Tergite 4 badly damaged, with median spine posteriorly. Tergites 5–6 unarmed, smooth. Telson subdivision distinct, with 12 plates.

Eye: Maximum corneal diameter one-third distance between apices of anterolateral spines; eyelashes absent; peduncle glabrous.

Antennule: Basal article elongated, slightly overreaching cornea; distomesial spine short; distolateral spine about twice length of distomesial spine; midlateral margin with distinct spines, distal longest.

Antenna: Distomesial spine of basal article sharp, reaching beyond midlength of article 2. Article 2 with distolateral and longer distomesial spine; distolateral spine overreaching article 3; distomesial spine overreaching article 4. Articles 3–4 unarmed. Flagellum, short, distalmost segments broken; flagellum apparently shorter than carapace length.

Maxilliped 3: Ischium with strong distal flexor spine; extensor margin unarmed. Merus ovate, with promiment, slender flexor plus distal extensor spine; length (excluding spines) 1.6 times width. Carpus with distal extensor spine. Crista dentata with row of low denticles.

Pereopods 1, 2, 4, 5: Not known.

Pereopod 3: Compressed, articles with sparsely distributed plumose setae, extensor margin of merus with several long iridescent setae. Merus length (excluding spines) about 4 times width, extensor margin with row of 7 or 8 graded spines, distalmost longest; flexor margin with sharp distal spine, otherwise unarmed. Carpus extensor margin with row of 4 spines including distal spine. Propodus 6 times as long as wide, 0.8 times merus length; extensor margin unarmed, sparsely setose; flexor margin with 6 small movable spines and 2 movable spines. Dactylus broken distally; flexor margin with at least 5 small movable spines; extensor margin crenulated.

Pereopod 5: Not known.

Etymology. Derived from the Greek, adelos, for “unknown” or “obscure”, alluding to the largely unknown features of the pereopods.

Remarks. We describe a new species based on the present incomplete specimen with some hesitation. The specimen remains are sufficient, however, to identify it as new, best placed in Crosnierita . The absence of most pereopods, especially the chelae of pereopod 5, which usually carry diagnostic genus characters, unfortunately renders generic assignment somewhat provisional. Of the three other known species of the genus, C. adela sp. nov. resembles C. dicata Macpherson, 1998 , and C. tucanae Macpherson, 2004 , and differs from C. yante (Macpherson, 1994) and C. urizae (Macpherson, 1994) in having prominent cardiac and gastric spines. It differs from both C. dicata and C. tucanae in having broad and stout, rather than slender, anterolateral spines on the carapace; two rather than three or one cardiac spines, respectively; and a median spine on the posterior ridge of the carapace. The new species further differs from C. dicata in the smooth (with only a few short striae anteriorly) rather than densely striated sternal plastron, and further differs from C. tucanae in having one instead of two lateral spines on the anterior ridge of abdominal somite 2. The setation of the pereopod 5 chelae is unfortunately presently unknown in C. adela .

Crosnierita adela superficially resembles some species of Bathymunida , B. avatea in particular, in the crested shape of the median gastric and cardiac processes on the carapace, and presence of a median posterior spine on abdominal tergite 4 (present in all Crosnierita but within Bathymunida , unique to B. avatea ). Crosnierita adela is readily distinguished from B. avatea based on other generic characters of Crosnierita such as the well-developed supraorbital spines (short, low in Bathymunida ), prominent extensor marginal spines on the walking legs (absent or poorly developed in Bathymunida ), well-developed lateral spines on the basal antennular article (absent or poorly developed in Bathymunida ) and distinctly subdivided telson (indistinct in Bathymunida ).

Distribution. Presently known only from the type locality, off north-western Australia; 258– 271 m.

Figures

FIGURE 2. Crosnierita adela sp. nov., male holotype, cl 12.7 mm, pcl 9.0 mm (NMV J 56116). A, dorsal habitus; B, right orbit, dorsal view; C, right lateral habitus; D, sternal plastron, damaged; E, telson; F, left antenna and antennule, ventral view; G, left maxilliped 3; H, left crista dentata; I, right pereopod 3. Scale: A – C, I = 5.0 mm; D – G = 2.5 mm; H = 1.0 mm.