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

Intercristacoxa orientalis sp. nov. Figs 2, 3, 4, 5, 6, 7, 8, 10 Type locality. Subtidal, site A (37°14'22.69"N, 131°51'53.09"E, Fig. 1), depth 7–10 m, sand between cracks in stone, 16 November 2017. Type material. Holotype: • 1 ♀ (MABIK CR 00258585), dissected on nine slides. Paratypes: • 1 ♂ (MABIK CR 00258583), dissected on nine slides; • 1 ♀ (MABIK CR 00258584), dissected on eight slides for confirmation. 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 210751, PX 210752, PX 485055 – PX 485058) and 18 S ribonucleic acid genes (PX 218728 and PX 218729). Description. Female. Total body (Fig. 2 A, B) nearly cylindrical, with minute sensilla dorsally, covered by pattern of sensilla and pores as illustrated, length from anterior margin of rostrum to posterior margin of caudal rami 1,000 μm, maximum width 180 μm measured at midway of cephalothorax; hyaline frill bumpy (Fig. 2 C); rostrum (Fig. 2 D) well developed, defined at base, triangular, with distal third tapering, with two sensilla; cephalothorax wider than free somites (Fig. 2 A), pleural areas of cephalic shield narrow and posterolateral angles rounded; second and third urosomites (genital double somite) separated dorsally and laterally (Fig. 2 A, B), fused ventrally but discontinuous internal chitinous rib indicating original segmentation (Fig. 5 A), genital apparatus located mid-ventrally at anterior half of genital double somite, genital pores covered by P 6 (Fig. 5 E); anal operculum not developed (Fig. 3 D). Caudal rami (Figs 3 D, 5 B), parallel, ~ 2.6 × longer than maximum width, surface armed with minute spinules (also see Fig. 10 C in male); each ramus with seven setae; seta IV fused at base to seta V; seta V bi-articulated, consists of spine-like seta at top and small pinnate seta attached at end (Fig. 2 E); seta VI bare at inner distal corner, seta VII tri-articulate at base, positioned dorsally on upper one – third of caudal rami. A 1 (Figs 3 A, B, 9 A); slender, four-segmented; seg – 1 large, with one thorn-like process at distal outer corner; seg – 3 with sub-cylindrical pedestal with ae fused at base to one long naked seta; seg – 4 representing two fused segments but middle horizontal ridge indicating original segmentation; armature formula: 1 – [1], 2 – [8], 3 – [9 + (1 + ae)], 4 – [13], apical ae not observed. A 2 (Fig. 3 C): allobasis with two rows of spinules, without abexopodal setae; exp one-segmented, with two bare setae; and enp with four spines, three geniculate setae, and one bare seta. Labrum (Figs 4 A, 9 B): dense pattern of blunt processes in middle and distal patches of overlapping scales. Md (Fig. 4 B): gnathobase small, with one uni-pinnate seta laterally and several multi-cuspidate teeth; palp basis with one bare seta on inner margin; enp one-segmented, with three bare setae; exp incorporated into basis, represented by small protrusion with one bare seta. Mxl (Fig. 4 C, D): praecoxa trapezoidal; arthrite well developed with two juxtaposed bare setae on anterior surface, two pinnate setae laterally, and six elements along distal margin, ornamented with a row of setules along inner margin; coxa with one bare and one pinnate setae; basis with three distal setae fused at base and two proximal setae; enp incorporated in basis, represented by small protrusion, with one pinnate and two bare setae; exp one-segmented, with one bare and one pinnate setae. Mxa (Fig. 4 E): 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 (Figs 4 F, 9 C): three-segmented; syncoxa with one pinnate seta; basis slender, elongate, bare; enp represented by an acutely recurved claw with two accessory setae. P 1 (Figs 6 A, 9 C – E): coxa with two serrate crests (Fig. 9 C, white arrow); basis with one outer and one inner pinnate setae, ornamented with small frills on base of enp (Fig. 9 D); exp one-segmented, with three outer and two apical setae, ornamented with two protuberances (Fig. 9 D, white arrow); enp two-segmented, prehensile; enp – 1, elongate, ~ 5.2 × as long as wide, bare; enp – 2, rectangular, with one curved claw and one seta (Fig. 9 E). P 2 (Fig. 6 B): coxa bare; basis with one outer pinnate seta; exp one-segmented, with three spines and two pinnate setae, ornamented with a tuft of setules laterally; enp absent. P 3 (Fig. 6 C): coxa bare, basis with one outer bare seta; exp one-segmented, with two outer spines and four pinnate setae; enp one-segmented, with three pinnate setae. P 4 (Figs 6 D, 9 E): coxa bare; basis with one outer bare seta; exp one-segmented, with two outer spines and four pinnate setae; enp one-segmented, with two pinnate setae. Armature formulae as follows: P 5 (Figs 5 C, D, 9 F): basal part with one outer bare seta; endopodal lobes not fused medially, connected by intercoxal sclerite, with five pinnate setae; length of middle seta abnormal in paratype (Fig. 5 D, black arrow); exp defined at base, with six pinnate setae. P 6 (Fig. 5 A, E): P 6 vestigial represented by a small bump with two bare setae. Male. Total body length (Figs 7 A, 10 A) from anterior margin of rostrum to posterior margin of caudal rami 810 μm, maximum width 133 μm measured at midway of cephalothorax. General body shape, ornamentation, and sensilla patterns as in female, except for genital double somite; sexual dimorphism in A 1, P 3, P 4, P 5, and P 6. A 1 (Figs 7 C – G, 10 B), six segmented, robust, chirocer; seg – 1 with one thorn-like process at distal outer corner; seg – 5 swollen, with pad-like process near anterior margin; three processes in middle; ae fused at base to one bare seta, armature formula: 1 – [1], 2 – [9], 3 – [6], 4 – [2], 5 – [11 + (1 + ae)], 6 – [11], apical ae not observed. Rostrum (Fig. 7 B): apically blunter than that of female. Setal formula and general shape of P 1 and P 2 similar to those of female. P 3 (Figs 8 A, B, 10 D): coxa bare; basis with one outer bare seta; exp one-segmented, with two spines and four setae; enp two-segmented; enp – 1 small, bare; enp – 2 elongated, armed with spinous apophysis, one lateral pinnate, and one apical minute setae. P 4 (Figs 8 C, 10 E): coxa bare; basis with one outer bare seta; exp one-segmented, with two spines and four setae; enp one-segmented, with one apical seta (stouter than female) and two lateral pinnate setae. P 5 (Figs 8 D, 10 F): benp presented by a small protrusion with two pinnate setae; exp defined at base, with four pinnate setae. P 6 (Figs 8 E, 10 F): asymmetrical, with functional right member articulating at base and closing off genital aperture, and left member fused at base to genital somite; P 6 with two pinnate setae. Etymology. The specific name is derived from the Latin adjective orientalis, meaning eastern, referring to the type locality in East Asia.