Tetragoniceps bermudensis Mussini, Niimi, Khodami, Kihara, Arbizu & Blanco-Bercial, 2025, sp. nov.

Tetragoniceps bermudensis sp. nov. Type locality. Bermuda, Roadside Cave (32.3468, -64.7131). Type material. Holotype, ovigerous female bearing egg sac. National Museum of Natural History (USNM 1752730). Etymology. The specific name bermudensis refers to the place where the new species was found followed by the Latin suffix - ensis, i. e. living in, or coming from, Bermuda. It is an adjective in the nominative singular. Diagnosis. A Tetragoniceps with caudal rami approximately 10 times longer than wide, P 5 with baseoendopodite and exopodite not fused into a single plate, cephalothorax with smooth dorsal surface, last segment of exopodites of P 2 to P 4 with 1 inner seta, endopodites of P 2 to P 4 with setal formula 1.021, and P 5 exopodite with 6 setae. Description. Female (Figs 3, 4). Total body length from base of rostrum to end of caudal rami approximately 750 µm. Body slender, subcylindrical, with no demarcation between metasome and urosome (Fig. 3), transparent when alive. Body surface smooth, with sensilla pattern as figured (Figs 3 A, B, 4). Body with 9 somites (prosome with cephalosome and P 1 - bearing somite fused, forming a cephalothorax, and with P 2 to P 4 bearing somites; urosome with P 5 - bearing somite, genital somite, 3 free urosomites, and anal somite with caudal rami). Posterior margin of body somites 4–8 with serrate hyaline frills. Urosome (Figs 3 A – C, 5 A, B) 5 - segmented, comprising P 5 - bearing somite, genital double-somite, 2 free abdominal somites, and anal somite. Genital field located medially, on anterior half of genital double-somite, with small median copulatory pore and paired genital pores laterally (Fig. 5 A). Anal operculum convex, with a row of fine spinules on distal margin (Fig. 5 B). Caudal rami (Figs 3 A – C, 5 B, C) approximately 10 times as long as wide at the widest portion (proximal end). Each ramus with 6 setae. Seta I completely reduced. Seta II laterally within the proximal half of each ramus. Seta III of similar length as seta II and located laterally within the terminal 20 % of each ramus. Dorsal seta VII longer than seta V, multi-articulated. Setae IV – VI arising apically, with IV and VI reduced in size and <30 % the length of seta V. Rostrum (Fig. 6 A) rounded, symmetrical, and distally concave; it bears 2 sensilla located near the outer margin. Antennule (Fig. 6 A) 9 - segmented. First segment elongate, with dentiform projection at outer distal corner. Aesthetascs on fourth and ninth segment. Armature formula 1 - [1], 2 - [8], 3 - [8], 4 - [2 + ae], 5 - [1], 6 - [3], 7 - [2], 8 - [1], 9 - [4 + ae]. Antenna (Fig. 6 B) with small, rectangular coxa and with long basis. Exopodite 1 - segmented, with 2 long bipinnate setae apically and 1 shorter unipinnate seta laterally. Endopod 2 - segmented. First endopodal segment unarmed. Second endopodal segment armed with 8 geniculate setae arising apically, the outer of which is basally fused with a slender seta, and armed with a small spinule on inner margin. Mandible (Fig. 7 A) with large sclerotised gnathobase. Pars incisiva with several acute teeth and several accessory spinules and dentations. Basis with 3 setae. Exopod short, 1 - segmented, with 1 small outer seta and 2 terminal setae. Endopod 1 - segmented, with 1 lateral and 5 terminal setae. Maxillule (Fig. 7 B) with praecoxa with arthrite armed with 6 distal spines, 2 bare terminal setae, and 1 subterminal bare seta. Coxal endite with 2 bare and 3 bipinnate terminal setae. Coxal epipodite represented by 1 bare seta. Basis with 4 bare, 1 unipinnate, and 2 geniculate terminal setae. Endopodite absent. Exopodite with 1 simple and 2 bipennate setae, and a row of long inner setules. Maxilla (Fig. 7 C), syncoxa with 3 endites, the first (proximal) bilobed, proximal lobe with two, distal lobe very reduced and armed with 1 seta. Second endite with 1 unipinnate and 1 bare seta. Third endite with 1 unipinnate and 2 bare setae, one shorter than the others. Allobasis with a claw-like spine, 1 long unipinnate seta, 1 long bare seta, and 2 short bare setae. Endopodite 1 - segmented, with 6 terminal setae. Maxilliped (Fig. 7 D) subchelate. Syncoxa with 2 pinnate setae distally. Basis showing the following proximo-distally: a row of several spinules, a long spine, a long seta, and a distal spinule. Endopodite 2 - segmented, second segment with 1 terminal claw, 1 terminal unipinnate seta, and 1 subterminal bare seta. P 1 (Fig. 8 A) coxa bare, basis with 1 bare outer seta. Endopodite 2 - segmented, exopodite 3 - segmented. First endopodal segment with outer setules, and 1 large inner bipinnate seta. Second endopodal segment with outer setules, and 2 geniculate unipinnate setae distally. First and second exopodal segments with 1 outer spine; first segment without, second segment with inner and outer setules. Third exopodal segment with 1 outer spine, 2 geniculate setae and 1 unipinnate seta distally, and both inner and outer margin setules. Setal formula listed in Table 1. P 2 (Fig. 8 B) coxa bare, basis with 1 bare outer seta and armed with 2 short spinules surrounding the endopodite. Endopodite 2 - segmented, exopodite 3 - segmented. First endopodal segment with 1 large inner seta. Second endopodal segment with inner setules, 1 outer spine and 2 bipinnate setae distally. First exopodal segment with a distal spinose outgrowth, 1 large outer spine, and an outer spinule. Second exopodal segment with a distal spinose outgrowth, 1 large outer spine, 1 pinnate inner seta, and a row of outer margin spinules. Third exopodal segment with 3 outer spines, 1 pinnate inner seta, 1 outer apical spine, 2 distal bipinnate setae, and rows of both inner and outer margin spinules. Setal formula listed in Table 1. P 3 (Fig. 8 C) coxa bare, basis with 1 bare outer seta. Endopodite 2 - segmented, exopodite 3 - segmented. First endopodal segment with 1 large inner seta. Second endopodal segment with 1 distal outer spine and 2 bipinnate setae distally. First exopodal segment with a distal spinose outgrowth and 1 large outer spine. Second exopodal segment with a distal spinose outgrowth and 1 large outer spine, 1 pinnate inner seta, and a row of outer spinules. Third exopodal segment with 3 large outer spines, 1 pinnate inner seta, 1 subapical bipinnate seta, 2 distal unipinnate setae, and a row of outer margin spinules. Setal formula listed in Table 1. P 4 (Fig. 8 D) coxa bare, basis with 1 bare outer seta and armed with short spinules surrounding the endopodite. Endopodite 2 - segmented, exopodite 3 - segmented. First endopodal segment with 1 inner unipinnate seta and short distal spinules. Second endopodal segment with 1 outer spine and 2 bipinnate setae distally. Exopodite approximately 3 times as long as the endopodite. First exopodal segment with a distal spinose outgrowth and 1 large outer spine. Second exopodal segment with a distal spinose outgrowth and 1 large outer spine, 1 pinnate inner seta, and rows of both inner and outer spinules. Third exopodal segment with 1 small outer spine, 1 unipinnate inner seta, 2 bare setae subapically, 3 unipinnate setae distally, and rows of both inner and outer spinules. Setal formula listed in Table 1. P 5 (Fig. 8 E), baseoendopodite very pronounced, armed with 1 outer basal seta; endopodal lobe with 1 long, bare seta apically and 1 small seta subapically, and with 3 setae on the inner margin. Exopodite pronounced, elongate, with 6 setae. P 6 (Fig. 5 A) each with rudimentary lobe carrying 2 bare setae, fused to basal plate.