Oncopagurus petilus, Lemaitre, 2014

Lemaitre, Rafael, 2014, A worldwide taxonomic and distributional synthesis of the genus Oncopagurus Lemaitre, 1996 (Crustacea: Decapoda: Anomura: Parapaguridae), with descriptions of nine new species, Raffles Bulletin of Zoology 62, pp. 210-301 : 267-273

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Oncopagurus petilus

new species

Oncopagurus petilus , new species

Figs. 31–34 View Fig View Fig View Fig View Fig , 51 View Fig

Type material. Holotype, eastern Pacific , SEPBOP, R/ V Anton Bruun, cruise 18B, sta 770, [off Ecuador], 03°15'S, 80°55'W, 945–960 m, trawl, 10 September 1966: M 4.6 mm ( USNM 1207983 View Materials ). GoogleMaps

Paratype, same sta as holotype: M 5.2 mm ( USNM 1207984 View Materials ) .

Description. Gills biserial. Shield ( Fig. 31A View Fig ) about as long as broad; dorsal surface weakly calcified medially, with scattered short setae; rostrum broadly rounded, weakly produced, with short mid-dorsal ridge; anterior margins weakly concave; lateral projections bluntly subtriangular; anterolateral margins sloping; posterior margin broadly rounded; ventrolateral margins of shield usually with small slender spine on one or both sides. Anterodistal margin of branchiostegite rounded, unarmed, setose.

Ocular peduncles ( Fig. 31A View Fig ) more than half length of shield, decreasing in width distally; with longitudinal row of long setae dorsally. Cornea not dilated, about as wide as distal width of peduncle. Ocular acicles subtriangular, each terminating in strong spine; separated basally by about basal width of 1 acicle.

Antennular peduncle ( Fig. 31A View Fig ) exceeding distal margin of cornea by 0.7 to nearly full length or ultimate segment when fully extended. Ultimate segment slightly less than twice as long as penultimate segment, with setae dorsally. Basal segment with strong ventromesial simple or bifid spine; lateral face with distal subrectangular lobe armed with small spine, and strong spine proximally. Ventral flagellum with 6 articles.

Antennal peduncle ( Fig. 31A, B View Fig ) exceeding distal margin of cornea by about half length of fifth segment when fully extended. Fifth segment unarmed except for scattered setae and laterodistal tuft of setae. Fourth segment armed with dorsodistal spine. Third segment with strong ventromesial distal spine. Second segment with dorsolateral distal angle produced, terminating in strong, simple spine; mesial margin with spine on dorsodistal angle. First segment with lateral face armed with small spine; ventromesial angle produced, with 2 small blunt spines laterally. Acicle long, exceeding distal margin of cornea by nearly half length of acicle, weakly curved outwardly (in dorsal view), terminating in strong spine; mesial margin armed with 6–9 spines, setose. Flagellum well exceeding extended right cheliped, articles with numeorus setae 1 or 2 flagellar articles in length.

Mandible ( Fig. 32A View Fig ) with 3-segmented palp; cutting edge calcified, with small calcareous tooth medially; molar process with small calcareous or corneous tooth medially. Maxillule ( Fig. 32B View Fig ) with external lobe of endopod obsolete, internal lobe with long, terminal seta. Maxilla ( Fig. 32C View Fig ) with endopod not exceeding distal margin of scaphognathite. First ( Fig. 32D View Fig ) maxilliped with endopod not exceeding exopod in distal extension. Second maxilliped ( Fig. 32E View Fig ) without distinguishing characters. Third maxilliped ( Fig. 32F View Fig ) with merus to dactyl each distinctly longer than broad; crista dentata with about 12 sharp, unequal teeth diminishing in strength distally; basis with 1 small mesial spine; coxa with spine. Sternite of third maxillipeds with small spine on each side of midline.

Chelipeds markedly dissimilar. Right cheliped ( Fig. 33A–C View Fig ) massive, chela operculate; dorsal surfaces of merus, carpus and chela, with moderate setation, setae more dense on fingers. Fingers curved ventromesially, each terminating in small, usually blunt corneous claw; cutting edges with 2 or 3 large calcareous teeth and several irregularly sized smaller sharp or blunt calcareous teeth, with closely set minute corneous teeth distally (corneous teeth interspersed with small calcareous teeth on fixed finger). Dactyl about as long as mesial margin of palm, set at oblique angle to longitudinal axis of palm; mesial margin broadly curved, well delimited by row of spines diminishing in size distally; dorsal face smooth except for setae; ventromesial face concave proximally. Fixed finger broad at base, dorsal face smooth except for setae, lateral margin well delimited by row of spines; ventral face elevated longitudinally on midline. Palm about as broad as long; dorsal surface smooth except for short setae; dorsolateral margin nearly straigth, well delimited by row of calcareous spines, dorsomesial margin delimited by row of small spines or tubercles; dorsomesial face nearly flat, slightly sloping mesially, with few, scattered small tubercles; ventral surface smooth except for scattered short setae. Carpus about 1.7 times as long as broad, dorsal surfaces covered with moderatley dense small spines or tubercles, dorsodistal margin with row of small spines; dorsolateral and dorsomesial faces rounded, with scattered small tubercles; ventral face slightly concave, with scattered small tubercles or spines. Merus with small spines or tubercles on dorsal surfaces, dorsodistal margin with row of small spines; ventromesial margin with row of blunt to sharp spines. Ischium with ventromesial row of small, blunt spines. Coxa with ventromesial row of setae and 2 small spines on lateral angle of ventrodistal margin.

Left cheliped ( Fig. 33D View Fig ) with moderately dense, long setae on dorsal margins of merus and carpus. Fingers each terminating in small corneous claw; dorsal and ventral surfaces unarmed except for scattered tufts of setae; cutting edge of dactyl with row of minute, fused corneous teeth; cutting edge of fixed finger with row of well-spaced small calcareous teeth. Dactyl about as long as length of mesial margin of palm; with setae dorsally. Palm unarmed dorsally except for dorsomesial setae; ventral face smooth. Carpus with dorsodistal spine; ventral face smooth. Merus unarmed dorsally except for seate; ventral face unarmed. Ischium and coxa unarmed except for ventromesial row of setae.

Ambulatory legs ( Fig. 34A–D View Fig ) similar right from left except for longer segments on right, extending to about tip of dactyls of right cheliped or slightly exceeding them; meri, carpi and propodi with setae on dorsal margins. Dactyls ( Fig. 34B, D View Fig ) broadly curved, about 1.5 times as long as propodi, terminating in sharp corneous claws; with dorsal and distal ventromesial row of setae, and 5–8 minute spinules on ventromesial margin. Propodi unarmed except for setae. Carpi unarmed except for setae and small dorsodistal spine. Meri unarmed except for setae and 2 or 3 small ventrodistal spines. Ischia with setae dorsally and ventrally, and small ventrodistal spine. Coxae with ventromesial row of setae. Anterior lobe of sternite XII (between second ambulatory legs, Fig. 31C View Fig ), setose, with subdistal spine.

Fourth pereopod ( Fig. 34E View Fig ) semichelate. Dactyl terminating in sharp corneous claw; with ventrolateral row of small corneous spinules. Propodus longer than broad, rasp with 1 row of rounded scales at least distally. Carpus with long setae on dorsal margin. Merus with rows of long setae on dorsal and ventral margins. Coxa with anteroventral row of setae. Anterior lobe of sternite XIII (between fourth pereopods, Fig.31C View Fig ) with row of setae.

Fifth pereopod ( Fig. 34F View Fig ) semichelate. Propodal rasp reaching to about mid-length of segment. Coxa with row of long setae on anteroventral and ventrodistal margins. Anterior lobe of sternite XIII (betwen fourth pereopods, Fig. 31C View Fig ) with row of setae.

Uropods markedly asymmetrical; left exopod ( Fig. 31D View Fig ) about 2.5 times as long as broad, rasp consisting of 3 or 5 rows of small scales. Telson ( Fig. 31E View Fig ) moderately asymmetrical, without transverse suture; dorsal surface with scattered setae; lateral margins with long setae medially; posterior lobes separated by shallow unarmed, U-shaped cleft; terminal margin of left lobe armed with 8 corneous spines, some slightly curved, terminal margin of right lobe with 5 small corneous spines.

Male with paired first and second gonopods; first gonopod ( Fig. 31F View Fig ) with distal portion subovate, and setose distal margins; second gonopod ( Fig. 31G View Fig ) with distal segment flat and with long setae distally, proximal segment with long setae distomesially. Females unknown.

Colouration. Unknown.

Habitat. Presumably gastropod shells.

Distribution. So far known only from the eastern Pacific, off Ecuador. Depth: 945– 960 m.

Remarks. The shape and relative length of the ocular peduncles, reduced corneas and long acicles exceeding the distal margins of the corneas of this new species, are reminiscent of Parapagurus species. In those features it is unique among Oncopagurus species. Although three other species ( O. minutus , O. conicus , and O. elongatus , new species) also have reduced or subconical corneas, none have as long antennal acicles as O. petilus , new species, a character that makes this new species distinct from other congeners distributed in the eastern Pacific.

Etymology. The specific name, from the Latin, petilus , thin, makes reference to the relatively thin or slender right cheliped.

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