Catapagurus tenuilamina Komai & Miller & Malay 2022, n. sp

Catapagurus tenuilamina n. sp. (Figs. 1–4, 12A) Material examined. Holotype. SIO-BIC C14512, male (sl 2.7 mm), off Pagan Island, Northern Mariana Islands, station crab trap, 18.0865N, 145.7652E, 58–89 m, 19 June 2015, field no. S25713.2, DNA voucher. Description. Gills biserial, 11 pairs. Shield (Fig. 1A) approximately as long as broad; anterior margin between rostral lobe and lateral projections concave; anterolateral margins sloping, continuing to convex lateral margin; posterior margin roundly truncate; dorsal surface polished, with longitudinal rows of tufts of short setae posterior to lateral projections; carapace lateral lobes moderately narrow, well calcified. Rostral lobe rounded, not reaching lateral projections. Lateral projections broadly triangular, each with terminal, submarginal spine. Posterior carapace 0.6 length of shield; posterolateral plates moderately wide anteriorly, drawn out into relatively thin bands reaching to posterior margins, posterior median plate short, only weakly calcified. Ocular peduncles (Fig. 1A) 0.7 times as long as shield, widened distally, constricted proximal to base of corneas; corneal width 0.4 of peduncular length. Ocular acicles narrow, spike-like, reaching 0.3 length of ocular peduncles, terminating acutely; widely separated basally. Interocular lobe clearly visible in dorsal view. Antennular peduncles (Fig. 1A) overreaching distal corneal margin by full length of ultimate article and 0.2 of penultimate article. Ultimate article 0.5 times as long as shield, 5 times as long as distal height, with tuft of 3 moderately long setae at dorsodistal lateral angle; dorsal surface glabrous. Penultimate article almost glabrous. Basal article with slightly produced, acute ventrodistal margin; statocyst lobe weakly inflated in proximal half of article. Antennal peduncles (Fig. 1A, B) overreaching distal corneal margin by 0.3 length of article 5. Articles 5 and 4 with few setae. Article 3 with few setae on unarmed ventromesial distal angle. Article 2 with produced, spiniform dorsolateral distal angle falling far short of midlength of article 4; dorsomesial distal angle with small spine. Article 1 with small spine at dorsolateral distal angle. Antennal acicle reaching distal end of article 4 and overreaching corneal base, terminating in spine. Flagella broken off and not preserved. Maxilliped 3 (Fig. 1C, D) with endopod moderately slender; merus with small dorsodistal spine; ischium with crista dentata consisting of 5 small, well spaced teeth; accessory tooth small, subdistal in position. Right cheliped (Fig. 2A–D) long, moderately stout for genus. Chela elongate subovate in dorsal view, 2.7 times as long as wide. Dactylus 0.6 length of palm, with moderately long to long setae on every surface, terminating in blunt calcareous claw; dorsal surface slightly convex transversely, without spines or tubercles; dorsomesial margin not delimited; mesial and ventral faces also smooth; occlusal margin with 2 obtuse calcareous teeth, slightly overlapped by fixed finger. Palm shorter than carpus, 1.8 times as long as wide; dorsomesial and dorsolateral margins not delimited, gently convex dorsal surface covered with minute granules extending onto lateral surface, and with few setae near base of fingers; mesial faces smooth ventrally; ventral surface gently convex, with scattered short to moderately long setae; fixed finger terminating in blunt calcareous claw, with sparse tufts or individual setae on every surface, occlusal margin with obtuse calcareous tooth at midlength, entire margin minutely denticulate. Carpus subequal in length to merus, widened distally, 2.6 times as long as distal width; dorsomesial and dorsolateral margins each delimited with row of tiny spines or tubercles, strongest distally, and with few short setae; dorsolateral margin more strongly elevated than dorsomesial margin; dorsal surface with scattered granules; lateral surface with scattered granules, ventromesial distal angle with 2 spinules; mesial surface with row of granules adjacent to dorsal margin and scattered granules distally, ventromesial distal angle with short row of 4 tubercles; ventral surface gently convex, smooth. Merus subtriangular in cross section; dorsodistal margin with conspicuous spine; dorsal surface with few subdistal transverse ridges followed by row of evenly spaced setae; lateral surface with sparse granules in distal half, ventrolateral margin minutely granulated, with 1 distal spine; mesial surface granular ventrally, otherwise almost smooth, ventromesial margin with 1 triangular spine at distal angle, otherwise minutely granulated; ventral surface with sparse granules and few short setae. Ischium with 1 small spine on granulate ventral surface, other surfaces smooth. Coxa (Fig. 1E) armed with small spine on ventromesial angle. Left cheliped (Fig. 3A–D) slender, about 0.9 length of right cheliped. Chela 4.8 times as long as wide; fingers nearly straight in lateral view. Dactylus 1.3 times as long as palm, distally curved in dorsal view, terminating in small corneous claw; surfaces almost smooth, with sparse setae; dorsomesial margin not delimited; occlusal margin with row of minute corneous teeth over almost entire length. Palm 0.5 length of carpus, 4.7 times as long as wide; dorsomesial and dorsolateral margins not delimited, transversely convex dorsal surface with faintly granulate; ventral surface slightly convex, smooth; fixed finger with sparse short setae, terminating in small corneous claw; occlusal margin with row of minute corneous teeth over entire length. Carpus subequal in length to merus; dorsomesial and dorsolateral margins delimited with row of spinules or granules (increasing in size and acuteness distally), dorsal surface with scattered coarse granules; lateral surface coarsely granulate in upper half, almost smooth in lower half, distoventral margin spineless; mesial surface nearly smooth except for granules adjacent to dorsal margin; ventral surface smooth, distoventral margin also spineless. Merus dorsodistal margin with 1 small spine; dorsal surface with row of several setae; lateral surface with sparse granules, particularly on ventral part, nearly straight ventrolateral margin with 1 small spine distally; mesial surface almost smooth except for granulate ventral part, nearly straight ventromesial margin with 1 small distal spine; ventral surface coarsely granulate. Ischium with 1 small subdistal spine on ventrolateral margin; ventral surface minutely granulate, other surfaces smooth. Coxa (Fig. 1E) with small spine on ventromesial angle. Pereopods 2 (Fig. 4A, B) slender, overreaching tips of outstretched chelipeds. Dactyli narrowly blade-shaped (length 11.5 times of width), subequal in length to propodi; in dorsal view, straight; in lateral view, slightly curved ventrally; dorsal margin and ventral margins unarmed; mesial faces concave, each with row of 23 moderately spaced, spiniform setae adjacent to dorsal margin, row of 20 minute spiniform setae adjacent to ventral margin; lateral surfaces with sparse short setae in distal half (Fig. 4B). Propodi slightly more than twice length of carpi, slightly narrowing distally in lateral view; dorsal and ventral margins smooth, former with 1 minute spiniform seta located at distal 0.25; lateral and mesial surfaces smooth; ventral margins each with row of few, widely spaced minute spiniform setae. Carpi short, about half-length of meri; dorsal surfaces minutely granulate, with 1 small dorsodistal spine; otherwise almost smooth. Meri each with 1 small dorsodistal spine and 2 unequal subdistal spines (proximal one largest), dorsal surface otherwise almost smooth, with row of evenly spaced moderately long setae; lateral and mesial surfaces smooth except for minutely granulate ventral parts; ventral surfaces minutely granulate, ventrolateral distal angle with tiny spine. Ischia unarmed. Right pereopod 3 (Fig. 4C, D) generally similar to pereopods 2 in general setation and armature, but slightly longer. Dactylus narrowly blade-shaped (length 13.8 of width), 1.1 times as long as propodi; mesial faces concave, with row of 23 spiniform setae, increasing in length distally, adjacent to dorsal margin, and with row of 20 minute spiniform setae adjacent to ventral margin; lateral surface with sparse short setae on distal part (Fig. 4D). Propodus about twice length of carpi; dorsal margins with 2 widely spaced, minute spiniform setae (one at distal 0.25 and other at about mid-length) and 1 minute spiniform setae distomesially; ventral margins with 2 minute spiniform setae subdistally. Carpus about half-length of merus; dorsal surfaces minutely granular, with 1 small dorsodistal spine. Merus with small dorsodistal spine and 2 evenly spaced subdistal spines; ventrolateral distal margin with 1 small spine. Ischium longer than those of pereopods 2, unarmed, ventral margin gently concave. Left pereopod 3 broken off, not preserved. Pereopods 4 (Fig. 1F) weakly semichelate; dactyli each with well developed preungual process far extending well beyond tip of corneous claw; propodal rasp consisting of single row of corneous scales on distal 0.8 of ventral margin. Pereopods 5 chelate. Males with long right sexual tube (right coxa; Fig. 1G, H) curved dorsally over pleon and overreaching pleonal midline, terminus simple, glabrous. Left coxa (Fig. 1G) without gonopore, with longitudinal row of short setae on ventral surface laterally. Thoracic sternite 6 (Fig.1I) anterior lobe broadly rounded, faintly bi-lobate, much shorter than large posterior lobe. Sternite 8 (pereopods 5) (Fig. 1G) consisting of two small lobes separated by shallow median groove, each with small tubercles anteriorly. Pleon with small, uniramous unpaired left pleopods 3 and 4, no pleopod 5. Uropodal protopods not protruding posteriorly. Telson (Fig. 1J) with lateral indentations suggesting separation of anterior and posterior portions; posterior lobes separated by moderately deep U-shaped median cleft, each terminating in subacute tip; lateral margins rounded, not converging posteriorly, with few short setae; longitudinal terminal margins unarmed. Colouration in life. Fig. 12A. Body and appendages generally brown. Cornea brown-gray. Chelipeds ventral surface paler; meri dark tinge on lateral and mesial faces. Ambulatory leg dactyli semi-transparent, each with brown median stripe and row of brown spots dorsally; propodi each with 3 longitudinal stripes on pale brown background; carpi each with tinge of white on lateral surface; meri mottled with dark and light brown. Distribution. Presently known only from off Pagan Island, Northern Mariana Islands, at depth of 58– 89 m. Etymology. From the combination of the Latin words, tenuis (= slender) and lamina (= blade), in reference to the slender but blade-shaped dactyli of the pereopods 2 and 3 of the new species. Used as a noun in apposition. Remarks. Catapagurus was heretofore represented by 25 species worldwide, of which 22 species are known from the Indo-West Pacific region (Asakura 2001; McLaughlin 2004a; McLaughlin et al. 2010; Komai & Rahayu 2021). The genus is divided into two informal species groups on the basis of the shape of the ambulatory dactyli, viz., the C. ensifer Henderson, 1893 group and C. misakiensis (Terao, 1914) species group (cf. Asakura 2001; Komai & Takeda 2006; Nucci & Melo 2012; Komai & Rahayu 2021). Catapagurus tenuilamina n. sp. is referred to the C. ensifer group because of the blade-shaped dactyli of the pereopods 2 and 3. The following 11 species are referred to the C. ensifer species group: C. albatrossae (Asakura, 2001), C. alcocki McLaughlin, in Hogarth et al., 1998, C. ensifer, C. granulatus Edmondson, 1951, C. haigae (Asakura, 2001), C. insolitus Komai & Osawa, 2009, C. kosugei (Asakura, 2001), C. latus Komai & Rahayu, 2021, C. lewinsohni (Asakura, 2001), C. sharreri A. Milne-Edwards, 1880, and C. tuberculosus (Asakura, 1999). Among these species, Catapagurus tenuilamina n. sp. is morphologically most similar to C. granulatus in the elongate ocular acicles, the possession of a ventromesial distal spine on each coxa of cheliped, and the relatively slender ambulatory dactyli, compared with typical members of the group such as C. ensifer, C. haigae (Asakura 2001), and C. latus Komai & Rahayu, 2021, and the general configuration of the telson. Nevertheless, the new species differs from C. granulatus in the following minor particulars: the ultimate article of the antennular peduncle is much more slender in C. tenuilamina n. sp. than in C. granulatus (Fig. 1A, B versus Asakura 2001: fig. 19B); the occlusal margin of the right cheliped fixed finger is armed with one obtuse calcareous tooth at the middle and otherwise minutely denticulate in C. tenuilamina n. sp. (Fig. 2C), whereas it is armed with a row of several calcareous teeth of various size in C. granulatus (Asakura 2001: fig. 29C); the dactylus of the pereopod 3 is more slender in the new species than in C. granulatus (Fig. 4C, D versus Asakura 2001: fig. 36B); the merus of the pereopod 2 is armed with 2 subdistal dorsal spines in C. tenuilamina n. sp. (Fig. 4A), rather than only 1 subdistal spine in C. granulatus (Asakura 2001: fig. 40D); and the telson posterior lobes are devoid of a terminal spine in the new species (Fig. 1J), rather than armed with a distinct corneous spine terminally in C. granulatus (cf. Asakura 2001: Fig. 44B). Catapagurus granulatus is presently known only from Hawaii, of which endemism to the area is suggested.