Paguropsina, Lemaitre, Rafael, Rahayu, Dwi Listyo & Komai, Tomoyuki, 2018

Lemaitre, Rafael, Rahayu, Dwi Listyo & Komai, Tomoyuki, 2018, A revision of " blanket-hermit crabs " of the genus Paguropsis Henderson, 1888, with the description of a new genus and five new species (Crustacea, Anomura, Diogenidae), ZooKeys 752, pp. 17-97 : 64-65

Genus Paguropsina gen. n.

Diagnosis.

Thirteen pairs of quadriserial gills [no pleurobranchs on thoracomere VIII (last)], gills consisting of series of twin lamellae each deeply divided distally into finger-like extensions (e.g., Fig. 25E). Shield well calcified, subovate; dorsal surface somewhat vaulted. Rostrum prominent, subtriangular, arched, and dorsally ridged. Lateral projections of shield each terminating in short vertical keel-like ridge usually armed with few small spines. Branchiostegite with dorsal margin (e.g., Fig. 23B) divided into two calcified plates: one anterodorsal plate poorly delimited ventrally, followed by small, subtriangular plate with distinct central pit. Posterior carapace with well calcified posteromedian plate, and well calcified lateral lobe on each side adjacent to shield. Ocular peduncles stout, half length of shield; corneas strongly dilated (diameter typically ca. 0.8 times length of ocular peduncle, including cornea); ocular acicles relatively small, subtriangular, armed with small or often minuscule dorsodistal spine. Antennal peduncles slender, delicate, not exceeding distal margins of corneas; acicles short, not reaching level of cornea. Mouthparts: maxillule with well-developed and strongly recurved external lobe of endopod; maxilliped 1 with exopodal flagellum, endopod medially bent at nearly right angle, with distinctly developed epipod; maxilliped 3 ischium with well-developed crista dentata, lacking accessory tooth, exopod broad, ca. 2.4 times as long as broad. Epistome unarmed. Chelipeds symmetrical or nearly so, subequal in size, armed with scarce to moderately dense setation and numerous well-spaced small spines or tubercles; coxae each with ventral surface having uncalcified median longitudinal fissure starting on distal margin and incompletely covering length of ventral surface. Pereopods 2 and 3 long and slender; dactyl of pereopod 3 distinctly longer than dactyl of pereopod 2. Sternite XI (between pereopods 3; e.g., Fig. 21D) wide, separating coxae of pereopods 3 by length of 1 coxa; anterior lobe flat, consisting of narrow rod-like plate (typically 8-10 times as broad as long), posterior lobes weakly divided medially by shallow groove into two subrectangular (wider than long), glabrous lobes. Pereopod 4 chelate, extending to subdorsal position to manipulate carcinoecium, lacking rasp-like surfaces; dactyl with cutting edge unarmed; fixed finger with cutting edge unarmed or with 1 corneous spinules; coxae (e.g., Fig. 27B) with anteroventral margin sharply delimited, keel-like. Sternite XII (between pereopods 4; e.g., Fig. 21D, 27B) broad, ridge-like, weakly divided medially, with fringe of setae. Pereopod 5 chelate, with weakly developed propodal rasp. Pleon curling under but not dextrally or sinistrally twisted; pleonal somite 1 not fused to last thoracic somite, with partly calcified tergite and pleura. Male with well-developed paired gonopods 1 and 2, and reduced (uniramous or biramous) pleopod 3-5 on left side only, when present. Female with paired gonopores; with paired uniramous pleopods 1 modified as gonopods; left side with unpaired, well developed, biramous pleopods 2-4 (ovigerous), rarely with vestigial pleopod 5; right side with no unpaired pleopods 2-5; brood pouch large, covering pleopods 2-4 and entire egg mass. Uropods and telson symmetrical; exopods long, slender; endopod small, curved. Telson subrectangular, lacking or with obscure lateral indentations; posterior margin weakly divided into nearly straight or very broadly rounded lobes.

Type species.

Paguropsina pistillata gen. et sp. n. Gender: feminine.

Species included.

In addition to the type species, the genus includes P. inermis gen. et sp. n.

Etymology.

The generic name is derived from the genus name Paguropsis , and using the Latin feminine suffix -ina, in reference to the relatively small size of individuals of the two species of this new genus.

Distribution.

Subtropical to tropical western Pacific. Depth: 52 to 849 m.

Remarks.

The two new species included in this genus have relatively small specimens ranging in shield length from 1.8 to 6.1 mm, with subovate shields, and a general delicate morphology with slender antennal peduncles and pereopods 2 and 3, weakly armed chelipeds having short, simple setation not obscuring the surface features of the segments, stout ocular peduncles, and wide corneas. Aside from the general, subtle appearance, species of Paguropsina gen. n. can be separated from those of Paguropsis primarily by four characters that are drastically different from those in species of Paguropsis . These are: the shape of the gills (lamellae deeply divided distally into finger-like extensions vs. distally divided into filamentous or stub-like extensions in Paguropsis ); the shape of the exopod of the maxilliped 3 (broad, 2.4 times as long as broad vs. slender, 4 or more times as long as broad in Paguropsis ); the width of sternite XI (ca. length of one coxa of pereopods 3 vs. less than half length of one coxa in Paguropsis ); and armature of the cutting edges of dactyl and fixed finger of chela of pereopod 4 (cutting edges of dactyl and fixed finger unarmed or with one distinct corneous spinule vs. cutting edge of dactyl with row of small corneous spines and cutting edge of fixed finger with sharp spines arranged like bear claw in Paguropsis ). In several other respects species of Paguropsina gen. n. and Paguropsis also differ albeit the differences are more subtle. The lateral projections of the shield each terminate in a short vertical keel-like ridge in species of Paguropsina gen. n., whereas the lateral projections terminate in a small spines without a keel in Paguropsis species. Additionally, it appears based on the material examined of both new species herein described under this new genus, that the location of pleopods tends to be fixed on the left side [see “Variations” under each species), whereas in species of Paguropsis the pleopods can frequently be present on either side.