Trapezionida diluta, Macpherson & Rodríguez-Flores & Machordom, 2024

Macpherson, Enrique, Rodriguez-Flores, Paula C. & Machordom, Annie, 2024, DNA barcoding and morphology revealed the existence of seven new species of squat lobsters in the family Munididae (Decapoda, Galatheoidea) in the southwestern Pacific, ZooKeys 1188, pp. 91-123 : 91

Trapezionida diluta sp. nov.

Fig. 5

Trapezionida aff. gordoae : Machordom et al. 2022: table 2, suppl. figs S1-S6.

Material.

Holotype: New Caledonia. Lifou 2000 Stn DW 1462, 9 November 2000, 20°47.1'S, 167°03.2'E, 70-120 m: male, 4.3 mm (MNHN-IU-2016-9652) . Paratypes: New Caledonia. Lifou 2000 Stn DW 1462, 9 November 2000, 20°47.1'S, 167°03.2'E, 70-120 m: 3 males, 3.5-4.6 mm, 1 ovigerous female, 3.9 mm (MNHN-IU-2014-13974) .

Description.

Carapace: 1.2 × as long as broad, moderately convex, with a few secondary striae between main transverse ridges. Ridges with short non-iridescent setae and few scattered long iridescent setae. Intestinal region without scales. Gastric region with four or five pairs of epigastric spines, longest pair behind supraocular spines, one pair between longest pair; one median protogastric spine. One parahepatic, one anterior branchial, and one postcervical spine on each side. Frontal margins oblique. Lateral margins slightly convex and convergent posteriorly. First lateral spine at anterolateral angle, long, not reaching level of sinus between rostrum and supraocular spines; second spine well developed, in front of anterior branch of cervical groove, < ½ length of first spine. Branchial margins straight, with three or four spines. Rostrum spiniform horizontal, ~ 0.4-0.6 × length of remaining carapace, not dorsally carinated. Supraocular spines reaching midlength of rostrum and not reaching end of cornea, subparallel, slightly upwards directed. Pterygostomian flap unarmed, ending in round tip.

Thoracic sternum: 0.8 × as long as wide. Surface of thoracic sternites IV-VI smooth, only a few short scales on sternite IV. Sternite III 3.5 × as wide as long. Sternite IV trapezoidal, anterior margin contiguous to sternite III along ¾ of its length; 2.5 × as wide as long, and 2.0 × as wide as sternite III.

Pleon: Ridges of pleomeres unarmed; tergites II and III each with uninterrupted transverse ridge on tergite behind anterior ridge: tergites IV and V with anterior ridge only; posteromedian margin of tergite VI straight.

Eye: Ocular peduncle longer than broad. Cornea dilated; maximum diameter 0.4 × distance between bases of anterolateral spines.

Antennule: Article 1 (distal spines excluded) very long, ~ 0.5 × carapace length, 3.5 × as long as wide (excluding spines), clearly overreaching end of cornea, with two distal spines, mesial spine longer than lateral; two spines on lateral margin, proximal one short, located at midlength of segment, distal one long, not reaching end of distal spines.

Antenna: Article 1 with distomesial spine barely exceeding article 2. Article 2 with distomesial spine, exceeding article 3; distolateral spine as long as or slightly larger than distomesial, exceeding article 3. Articles 3 and 4 unarmed.

Mxp3: Ischium with well-developed spine on flexor distal margin. Merus shorter than ischium; flexor margin with two spines, median slightly stronger than distal spine; extensor margin unarmed. Carpus unarmed.

P1: 2.3-3.0 × carapace length, with scattered long plumose setae, and some long iridescent setae; some short setae on spines and scales. Merus 1.0-1.1 length of carapace, 2.0-2.2 × as long as carpus, with some dorsal and mesial spines; distal spines strong, distomesial spine barely reaching proximal fourth of carpus. Carpus 0.8-1.0 length of palm, 2.3-2.5 × as long as broad; with spines along mesial and dorsal sides. Palm 2.3-2.8 × as long as broad, with row of small dorsal spines; one row of spines along mesial and lateral margins, continuing along movable and lateral fingers, respectively. Length of fingers 1.1-1.3 × that of palm.

P2-P4: Long and slender, with some short setae and some scattered iridescent setae along extensor margins of all articles. P2 2.1-2.2 × carapace length. Meri shorter posteriorly (P3 merus 0.8-0.9 × length of P2 merus, P4 merus 0.8-0.9 × length of P3 merus); P2 merus 0.7-0.8 × carapace length, 5.8-6.5 × as long as broad, 1.2-1.3 × as long as P2 propodus; P3 merus 6.0-6.2 × as long as broad, 1.2-1.2 × as long as P3 propodus; P4 merus 4.5-4.7 × as long as broad, as long as P4 propodus. Extensor margins of meri with row of 5-7 proximally diminishing spines on P2-P3, one or two spines on P4; flexor margins with three or four spines followed proximally by several eminences; lateral sides unarmed. Carpi with three or four spines on extensor margin of P2-P3, one distal on P4; lateral surface with several granules sub-paralleling extensor margin on P2-4; flexor margin with well-developed distal spine. Propodi 6.5-7.6 × as long as broad; extensor margin unarmed; flexor margin with eight-ten slender movable spines on P2-P4, one fixed distal spine. Dactyli slender, length 0.7-0.8 × that of propodi; flexor margin with 10-11 movable spinules along entire border, with ultimate spinule at base of unguis, penultimate spine equidistant between antepenultimate and ultimate spines; P2 dactylus 7.4-7.5 × as long as wide. P4 merocarpal articulation exceeding anterior end of cervical groove; P4 merus> ½ length of P2 merus.

Genetic data.

COI, 16S.

Etymology.

From the Latin, dilutus, thin, in reference to the shape of the antennular peduncle.

Remarks.

Trapezionida diluta belongs to the group of species having the anterior ridge of the pleomere II tergite unarmed, the thoracic sternites smooth and the antennular article 1 very slender, exceeding eye, and with the distomesial spine longer than the distolateral spine. The new species is close to T. macilenta sp. nov., from Papua-New Guinea (see below under the Remarks of this species).

Distribution.

New Caledonia, 70-120 m.

Figures

Figure 5. Trapezionida diluta sp. nov., male holotype, 4.3 mm (MNHN-IU- 2016 - 9652), New Caledonia A carapace and pleon, dorsal view B sternal plastron C cephalic region, showing antennular and antennal peduncles, ventral view D right Mxp 3 ischium and merus, lateral view E right P 1, dorsal view F right P 2, lateral view G dactylus of right P 2, lateral view H left P 3, lateral view I right P 4, lateral view. Scale bars: 1.0 mm (A, B, F, H, I); 0.5 mm (C, D, G); 2.0 mm (E).