Intercristacoxa koreana Back & Bang, 2026, sp. nov.

Intercristacoxa koreana sp. nov. Figs 11, 12, 13, 14, 15, 16, 17 Type locality. Subtidal, site B (37°14'23.23"N, 131°52'20.06"E, Fig. 1), depth 7–10 m, sand between cracks in stone, May 16, 2017. Type material. Holotype: • 1 ♀ (MABIK CR 00258582), dissected on ten slides. Paratypes: • 1 ♂ (MABIK CR 00258579), dissected on nine slides; • 1 ♀ (MABIK CR 00258581), dissected on nine slides; • 1 ♂ (MABIK CR 00258580), dissected on five slides. Three specimens (1 ♀, 2 ♂♂) dried, mounted on stub, and coated with gold for SEM. GenBank accession number. Mitochondrial cytochrome c oxidase subunit I genes (PX 210748 – PX 210750, PX 485050 – PX 485054), 18 S ribonucleic acid genes (PX 218726, PX 218727, PX 485043 – PX 485045). Description. Female. Total body (Fig. 11 A, B), nearly cylindrical, with minute sensilla dorsally, length from anterior margin of rostrum to posterior margin of caudal rami 920 μm, maximum width 160 μm measured at end of cephalothorax; rostrum (Fig. 11 C) well developed, defined at base, triangular, with two sensilla; cephalothorax wider than free somites, pleural areas of cephalic shield narrow and posterolateral angles rounded; second and third urosomites (genital double somite) separated dorsally and laterally, fused ventrally but discontinuous internal chitinous rib indicating original segmentation (Figs 11 B, 12 C), genital apparatus located at anterior of genital double somite; anal operculum deeply curved (Fig. 12 D). Caudal rami (Fig. 12 C, D), parallel, rectangular, ~ 1.3 × longer than maximum width; each ramus with seven setae: seta I minute; seta II bare, laterally; seta III bare, located near distal corner; seta IV bare; seta V bi-articulated, consists of spine-like seta at top and small naked seta attached at end; seta VI bare at inner distal corner; seta VII tri-articulated at base, bare. A 1 (Figs 12 A, 17 A): four-segmented; seg – 1 with one thorn-like process at distal outer edge; seg – 3 longest, with sub-cylindrical pedestal with ae fused at base to one naked seta; armature formula: 1 – [2], 2 – [9], 3 – [9 + (1 + ae)], 4 – [14]; apical ae not observed, but two apical long setae fused at base. A 2 (Fig. 12 B): three-segmented; coxa bare; allobasis without abexopodal seta; exp one-segmented with two small setae; free enp with four spines, three geniculate setae, and one bare seta. Labrum (Fig. 13 A) with a dense pattern of blunt processes in middle and numerous spinules of overlapping scales. Md (Fig. 13 B): gnathobase developed, with one uni-pinnate seta laterally and several teeth; basis of palp with one bare seta along inner margin; enp one-segmented, with three bare apical setae; exp represented by one bare seta. Mxl (Fig. 13 C): praecoxa trapezoidal; arthrite well developed with two juxtaposed bare setae on anterior surface, two pinnate setae laterally, and six elements around distal margin; coxa with one bare and one pinnate seta; basis with four setae; enp incorporated in basis, represented by small protrusion with three bare setae; exp one-segmented, with two bare setae. Mxa (Fig. 13 D): syncoxa with three endites; proximal endite vestigial, represented by one seta; second endite with one strong spine and two bare setae; distal endite with three setae; allobasis produced into strong curved claw, accessory armature consisting of two setae; and enp represented by three bare setae fused at base. Mxp (Fig. 13 E): three-segmented; syncoxa with one pinnate seta; basis slender, elongate, and bare; enp represented by an acutely recurved claw with two accessory setae. P 1 (Fig. 14 A): coxa with two outer serrate crests; basis with one outer and one inner pinnate setae, ornamented with small frills on base of enp; exp one-segmented, with three outer and two apical setae, ornamented with two protuberances; enp two-segmented, prehensile; enp – 1 elongate, unarmed; enp – 2 rectangular, with one curved claw and one geniculate seta. P 2 (Fig. 14 B): coxa bare; basis with one outer pinnate seta; exp one-segmented, with three spines and two setae; enp absent. P 3 (Fig. 14 C): coxa bare; basis with one outer bare seta; exp one-segmented, with two outer spines, one bare seta, and two pinnate setae; and enp one-segmented, with two pinnate setae. P 4 (Fig. 14 D): coxa bare; basis with one outer bare seta; exp one-segmented, with two outer spines and three pinnate setae; enp one-segmented, with one pinnate seta. Armature formulae as follows: P 5 (Figs 14 E, 17 B): basal part with one outer bare seta; endopodal lobes not fused medially, connected by intercoxal sclerite, with four pinnate setae, an abnormality observed in second innermost seta of paratype (Fig. 14 F, black arrow); exp defined at base, with six pinnate setae. P 6 (Fig. 14 G): P 6 vestigial, represented by a small bump with two bare setae. Male. Total body (Fig. 15 A) length from anterior margin of rostrum to posterior margin of caudal rami 890 μm, maximum width 155 μm measured at midway of cephalothorax. General body shape, ornamentation, and sensilla pattern same as in females, except for genital double somites and sexual dimorphism in A 1, P 3, P 4, P 5, and P 6. A 1 (Fig. 15 B, C): six-segmented, robust, chirocer; seg – 1 with one thorn-like process at distal outer edge; seg – 5 swollen, with pad-like process near anterior margin, three processes in middle, and ae fused at base to one bare seta, armature formula: 1 – [1], 2 – [10], 3 – [6], 4 – [2], 5 – [9 + (1 + ae)], 6 – [12], apical ae not observed. Setal formula and general shape of P 1 and P 2 similar to those of female. P 3 (Figs 16 A, 17 C): coxa bare; basis with one outer bare seta; exp one-segmented, with two spines and three setae; enp two-segmented; enp – 1 small, bare; enp – 2 elongated, armed with spinous apophysis, with two lateral pinnate setae, and one apical minute seta. P 4 (Figs 16 B, 17 C): coxa bare; basis with one outer bare seta; exp one-segmented, with two spines and three setae, ornamented with setules along inner margin; enp one-segmented, with one apical (stouter than female) and two lateral pinnate setae. P 5 (Figs 15 D, 17 D): benp represented by a small protrusion with one pinnate seta; exp defined at base, with four pinnate setae. P 6 (Fig. 16 C): asymmetrical, with functional right member articulating at base and closing off genital aperture, and left member fused at base to genital somite; each P 6 with two pinnate setae. Etymology. The species name refers to the country of the type locality.