Catapagurus thysanodactylus, Lemaitre, 2025

Catapagurus thysanodactylus n. sp.

( Figs 4-6)

urn:lsid:zoobank.org:act:

TYPE MATERIAL. — Holotype. Philippines • ♂ 3.0 mm; Panglao Island , off San Isidro; PANGLAO 2004; stn T10 ; 09°33.4/33.8’N, 123°49.6/51.5’E; 117-124 m depth; 15.VI.2004; mud and fine sand; 15.VI.2004; MNHN-IU-2022-4539.

Paratypes. Philippines • ♂ 1.6 mm; same station as holotype; MNHN-IU-2022-4545 • 7♂ 1.9-2.4 mm, 6 ovig ♀ 1.8-2.3 mm; between Panglao and Pamilacan islands; PANGLAO 2004; stn T27 ; 09°33.4’N, 123°51.0’E; 106-137 m depth; fine sand and mud with echinoderms; 25.VI.2004; MNHN-IU-2022-4540 GoogleMaps .

ETYMOLOGY. — The specific epithet is from the Greek thysanos, meaning fringe, in reference to the fringe of setae present on the dactyls of pereopods 2 and 3.

DISTRIBUTION. — Known so far from south of Panglao Island, central Philippines; depth: 106- 137 m.

HABITAT. — Housing unrecorded, probably empty gastropod shells; on fine sand and mud, with echinoderms.

DESCRIPTION OF HOLOTYPE

Shield ( Fig. 4A)

Slightly broader than long; anterior margin between rostral lobe and lateral projections weakly concave; anterolateral margins sloping; posterior margin roundly truncate; dorsal surface slightly convex, smooth, with sparse tufts of moderate short setae. Rostral lobe broadly rounded, reaching about level of lateral projections. Lateral projections broadly triangular, terminating in small, sharp spine. Carapace lateral lobes narrow, reaching slightly beyond midlength of shield. Posterior carapace with poorly calcified median plate; cardiac sulci distinctly cal - cified, reaching posterior margin. Branchiostegites unarmed.

Ocular peduncles ( Fig. 4A)

Short, stout, 0.6 to 0.7 length of shield, broadened distally; cornea dilated, diameter approximately 0.7 of peduncular length; ocular acicles, slender, terminally acute, reaching approximately mid-length of ocular peduncles, naked, separated basally by twice basal width of acicle.

Antennular peduncles ( Fig. 4A)

Overreaching distal corneal margins by approximately half lengths of penultimate segments; dorsolateral surfaces and dorsolateral distal angles of ultimate segments naked or with few short setae; penultimate segment glabrous; basal segment with spine at ventromesial distal angle.

Antennal peduncles ( Fig. 4A)

Overreaching distal corneal margins by nearly full lengths of ultimate (fifth) segments; fifth and fourth segments naked or scattered short setae; third segment with ventrodistal angle produced, with blunt terminal spine; second segment with dorsolateral distal angle produced, terminating in strong spine, dorsomesial distal angle with small spine; first segment unarmed. Antennal acicles strong, weakly curved outward, reaching or slightly overreaching distal margins of corneas, with few distal setae; mesial and lateral faces unarmed. Antennal flagella reaching distal end of right chela; flagella naked or with scattered short setae each less than one flagellar article in length.

Mouthparts

Not dissected. Third maxilliped with basis bearing one spine-like tooth; ischium crista dentata with 6-8 teeth slightly increasing in size distally, and prominent accessory tooth; merus with blunt dorsodistal angle.

Chelipeds ( Fig. 5)

Distinctly dissimilar, sparsely setose; left considerably slenderer than right; fingers with scattered setae, each terminating in small, blunt corneous claw crossed when fingers closed.

Right cheliped ( Fig. 5A, B) elongate, exceeding left cheliped in distal extension by approximately half length of right dactyl. Dactyl approximately 0.6 length of palm; dorsal surface convex, mostly with scattered minute granules except for denser granulation on dorsomesial surface; mesial margin not delimited, rounded and minutely granular; ventral surface similar to dorsal; cutting edge armed with two larger, unequal calcareous teeth proximally, otherwise with small, closelyset, irregular calcareous teeth distally. Palm approximately 1.3 times as long as carpus; fixed finger with inconspicuous granular surfaces, cutting edge armed with one small calcareous tooth medially, and serrated small teeth distally; dorsal and ventral surfaces convex, glabrose, dorsomesial and dorsolateral margins not delimited; ventral surface weakly granular. Carpus slightly shorter than merus; dorsal, lateral and mesial surfaces minutely granulose, dorsolateral and dorsomesial margins faintly delimited by minute granules; ventral surface weakly granular. Merus triangular in cross-section; dorsal, lateral and mesial surfaces with minute granules, with sharp dorsodistal spine; lateral and mesial surfaces smooth or at most with scattered minute granules; ventral surface granular. Ischium with one row of small spines on ventrolateral margin. Coxa unarmed.

Left cheliped ( Fig. 5C) approximately same length as right when fully extended, sparsely setose; fingers crossing at tips when closed, each terminating in sharp, inwardly curved corneous claw. Dactyl approximately 1.5 times as long as palm; dorsal, mesial, and ventral surfaces nearly smooth or finely granular, with few scattered setae; cutting edge with one row of minute, closely set corneous teeth. Palm approximately 0.6 times as long as carpus; dorsal surface weakly convex; surfaces all finely granulose (granules more conspicuous on dorsomesial surface), with scattered setae; fixed finger with surfaces minutely granulose, cutting edge with more or less evenly and well-spaced minute calcareous teeth. Carpus slightly shorter than merus, surfaces minutely granulose (granules more conspicuous on dorsomesial surface); dorsomesial margin weakly defined, rounded; dorsolateral margin weakly delimited. Merus triangular in cross-section, surfaces minutely granulose; dorsodistal angle unarmed. Ischium unarmed. Coxa unarmed.

Ambulatory legs ( Fig. 6 A-D)

Pereopods 2 and 3 similar except pereopod 2 somewhat shorter. Dactyls slender, not blade-shaped; in lateral view slightly curving ventrally on distal one-third; subequal in length to propodi, each terminating in sharp corneous claw; dorsal and ventral margins each with fringe of short setae, ventromesial margins unarmed; lateral and mesial faces smooth. Propodi with surfaces smooth, with one row of short setae on dorsal and ventral margins. Carpi surfaces minutely granular, denser on dorsal surfaces; with blunt dorsodistal angle. Meri with surfaces smooth; dorsal margin with three conspicuous spines on distal third, sparsely setose; ventral margins with two or three minute spines medially (pereopod 2) or unarmed (pereopod 3).

Pereopod 4 ( Fig. 6E, F)

With distinctly developed preungual process at base of claw ( Fig. 6F); dactyl terminating in short, curved corneous claw; propodal rasp consisting of one row of ovate scales. Sternite of third pereopods ( Fig. 4B) with anterior lobe broadly subovate, setose distally.

Male pereopod 5, sexual tube, and pleopods ( Fig. 4B, C)

Male pereopod 5 with coxae ( Fig. 4B) roughly symmetrical; right coxa with sexual tube, left with gonopore obscured by fringe of setae; sexual tube ( Fig. 4B, C) long, slender, semitransparent, directed outward and curving over dorsal portion of pleon, terminating in curved finger-like tip. Male with three weakly developed left pleopods 3-5, pleopods 3 and 4 with rudimentary internal rami, pleopod 5 uniramous.

Females

With pleopods 2-5 (pleopods 2-4 ovigerous).

Uropods ( Fig. 4D)

Asymmetrical; exopods with moderately developed rasps.

Telson ( Fig. 4D)

Longer than broad, with distinct deep lateral indentations; posterior lobes acutely subtriangular, separated into two lobes by distinct, deep V-shaped median cleft, outer margins nearly straight; posterior lobes each terminating in sharp spine, inner margins with row of two or three bristle-like setae.

Color

Unknown.

REMARKS

Among the species of Catapagurus that do not have blade-like dactyls on the P2 and P3, this new species is morphological more similar to C. danida McLaughlin, 2002 . In this new species: the anterolateral projections each has a weak spine, whereas in C. danida the spine is larger; the cornea are dilated, whereas those of C. danida are at most slightly dilated; the dorsal surfaces of propodus and palm of the chelipeds are virtually smooth, whereas there are distinct spinules in C. danida ; the sinus separating the posterior lobes of the telson is V-shaped, whereas it is U-shaped in C. danida .