Leiocanthus satanicus Cepeda & Sánchez & Sørensen & Landers 2022, sp. nov

Leiocanthus satanicus sp. nov. Zoobank code: urn:lsid:zoobank.org:act: 9B48A215-F9C4-4BE2-8D5A-D650133B133 (Figs. 5–8) Synonymy Pycnophyes sp. A —Landers et al. 2018: Table 2. Leiocanthus W —in Landers et al. 2019: p. 5. Material examined. Holotype, adult female, collected on November 12, 2013 at St. 68-2013 in the northern Gulf of Mexico continental shelf: 29.2998° N, 88.7200°W (Table 1) at 59 m depth; mounted in Fluoromount G ®, deposited at the NHMD under catalogue number: NHMD-915202. Paratypes, three adult males and six adult females, one of the females collected at the same station as the holotype, remaining specimens collected at different stations (Table 1), mounted in Fluoromount G ® and deposited at NHMD under catalogue numbers: NHMD-915203–915211. Two additional specimens, one male and one female, mounted for SEM and deposited in the personal reference collections of SCL and MVS. Diagnosis. Leiocanthus with middorsal cuticular elevations on segments 1–6. Unpaired paradorsal setae on segments 4 and 6; paired setae in subdorsal position on segments 2, 4, 6 and 8, in laterodorsal position on segments 3, 5, 7 and 9, paralateral position on segment 1, lateroventral position on segments 2, 4, 6, 8 and 10 (two pairs in the latter), ventrolateral position on segments 1 and 5, ventromedial position on segments 4–7 and 9, and paraventral position on segments 3 and 8. Males with sexually dimorphic ventromedial tubes on segment 2, females with setae instead. Lateral terminal spines absent, minute and bulbous protuberances instead. Anterolateral margins of the tergal plate of segment 1 extended into horn-like, medially recurved, distally pointed projections; anterior margin of tergal plate strongly denticulated, posteriorly followed by a crenulated area; cuticular wrinkles at the central region of the tergal plate. Etymology. The specific epithet of the species refers to the Latin name Satâna, derived from the Hebraic הַשָּׂטָן (ha-shatán), which is a negative entity of the Abrahamic religions that seduces humanity to commit sin. Satan has been traditionally represented in graphic and literary arts as a fallen angel with conspicuous horns, which resembles the recurved anterolateral margins of the segment 1 tergal plate of the new species. Description. See Table 4 for measurements and dimensions and Table 5 for summary of seta, tube, glandular cell outlet, and sensory spot positions. Head. Only two specimens had the head everted, hence exact details on the morphology and arrangement of the mouth cone and introvert structures cannot be completely provided. Internal rings of mouth cone not observed. Ring 00 of mouth cone with nine, equally sized outer oral styles, each one composed of a single, flexible unit, wider at the base, bearing a fringed basal sheath, with a lateral incision about one third from the proximal end, progressively tapering towards a distally rounded tip (Fig. 6C). Outer oral styles located anterior to each introvert sector, except in the middorsal sector 6 where a style is missing. Introvert with six transverse rings of scalids and 10 longitudinal sectors defined by the position of the primary spinoscalids. Ring 01 with 10 primary spinoscalids, larger than the remaining ones, each one composed of a basal, rectangular, wide sheath and a distal, elongated, flexible, laterally compressed, distally rounded end-piece (Fig. 6D, F). Basal sheath of primary spinoscalids superficially fringed, bearing a rhomboid cuticular piece superficially fringed near the articulation point with the end-piece (Fig. 6D inset, F). Rings 02–06 with several regular-sized scalids, conspicuously smaller than the primary spinoscalids, also composed of a basal, rectangular, superficially fringed, wide sheath and a distal, elongated, flexible, distally rounded end–piece (Fig. 6F). Exact arrangement of regular-sized scalids cannot be provided due to the collapsed condition of the only available introverts. Despite this, the odd-numbered sectors seem to possess seven regular-sized scalids arranged as a double diamond (Fig. 6F). A ring of 14 trichoscalids posterior to the scalid rings (Fig. 6E), arranged as two in the odd-numbered sectors (except sector 1 with a single trichoscalid) and one in the even-numbered sectors of the introvert. Neck. Neck with four dorsal and two ventral sclerotized placids (Figs. 5A–B, 6G–H). Mesial dorsal placids sub-quadrangular, conspicuously higher than lateral ones (Figs. 5B, 6G), ca. 33–41 μm wide at the base; lateral dorsal placids rectangular (Figs. 5B, 6G), ca. 23–26 μm wide at the base. Ventral placids even more rectangular, longitudinally compressed, with the posterolateral margins straight to slightly curved towards the sternal plates of the first trunk segment (Figs. 5A, 6H), ca. 21–30 μm wide at the base. Trunk. Trunk rectangular, stout, triangular in cross–section, composed of 11 segments (Figs. 5A–B, 6A–B, 8A). Segment 1 with one tergal, two episternal, and one midsternal plates; remaining segments with one tergal and two sternal plates (Figs. 5A–D, 6A–B, 7A–K, 8A–F). Maximum sternal width at segment 3 (Table 4), almost constant in width throughout the trunk until segment 3, and progressively tapering along the last trunk segments (Figs. 5A–B, 6A–B, 8A). Sternal cuticular plates relatively narrow in relation to trunk length (MSW–3:TL interval ratio = 21.8–26.8) (Table 4), giving the animal a relatively slender appearance (Figs. 5A–B, 6A–B, 8A). Segments 1–11 with glandular cell outlets with a single round to oval opening: segments 1 and 9–10 with these glandular cell outlets in subdorsal and ventromedial positions, segments 2–8 in subdorsal and paraventral positions, and segment 11 in subdorsal position (Figs. 5A–D, 7A–J); intraspecific variation of this character was found in a couple of specimens that showed up to three round openings per glandular outlet (Fig. 7D); in addition, in some specimens the bilateral pattern was lost as the glandular cell outlet was missing in one side of some tergal plates. Segments 2–10 with paired, small, not always conspicuous cuticular ridges in ventrolateral position, with adjacent, minute glandular cell outlets (Fig. 5A–D). Minute, acicular cuticular hairs, widely covering the cuticular surface of segments 1–10 (except the most anterior halves of the episternal plates of segment 1 where hairs are absent), denser at the tergosternal junctions (Fig. 8B–F). Males with sexually dimorphic longitudinal bands of cuticle densely covered by smaller acicular hairs in ventromedial position of segment 2, under the tubes (Fig. 8C). Very conspicuous, rounded to oval muscular scars without hair-covering in laterodorsal and ventromedial positions (Figs. 5A–D, 7A–J). Pachycycli and ball-andsocket joints well-developed and thick on segments 2–10 (Figs. 5A–D, 7A–H). Apodemes absent. Posterior margin of segments straight, with primary pectinate fringes showing weakly serrated free flaps (Figs. 5A–D, 7A–H, 8A–F). Secondary pectinate fringes as three (dorsal) to two (ventral) transverse rows, finely serrated, becoming wavier at the sternal plates, extending posteriorly in triangular extensions near the location of the muscular scars (Figs. 5A–D, 8C, E, F). Segment 1 with middorsal elevation not projecting beyond the posterior margin of segment, with conspicuous paradorsal, butterfly-like atria of sensory spots (Figs. 5B, 7A). Anterolateral margins of the tergal plate forming conspicuous horn-like, medially recurved, distally pointed projections (Figs. 5A–B, 6A–B, I, 8A–B). Anterior margin of tergal plate strongly denticulated, posteriorly followed by a crenulated area (Figs. 5B, 6K). Anterior margins of sternal plates with several, small, cuticular depressions and some semi-circular ridges (Figs. 5A, 6H). Characteristic cuticular wrinkles at the central region of the tergal plate in subdorsal towards laterodorsal position (Figs. 5B, 6K). Midsternal plate almost rectangular, not extended at its base, with a small lateral indentation near its anterior margin, and a straight posterior margin (Figs. 5A, 6B, 8A). Paired setae in paralateral and ventrolateral positions (Figs. 5A–B, 7A, 8B). Sensory spots in paradorsal (one pair), subdorsal (two pairs, longitudinally aligned), laterodorsal (one pair), paralateral (one pair), ventrolateral (one pair) and ventromedial (one pair) positions (Figs. 5A–B, 7A, 8B). Sensory spots on this and remaining segments oval, with up to three pores surrounded by several rings of micropapillae. Segment 2 with middorsal elevation as on the preceding segment (Figs. 5B, 7D). Paired setae in subdorsal and lateroventral positions; subdorsal setae more mesial than subdorsal sensory spots; ventromedial setae only in females (sexually dimorphic) and located more lateral than the ventromedial sensory spots (Figs. 5 A-C, 7B, D). Sensory spots in paradorsal (one pair), subdorsal (two pairs), laterodorsal (one pair) and ventromedial (one pair) positions (Figs. 5A–C, 7B, D, 8C). Males with conspicuously large, sexually dimorphic tubes in ventromedial position (Figs. 5A, 8C). Segment 3 with middorsal elevation as on the preceding segments (Figs. 5B, 7D). Paired setae in laterodorsal and paraventral positions (Figs. 5A–B, 7C–D, 8C). Sensory spots in paradorsal (one pair), subdorsal (two pairs), laterodorsal (one pair) and ventromedial (one pair) positions (Figs. 5A–B, 7C–D, 8C). Intraspecific variation in the arrangement of the laterodorsal setae has been observed in two specimens, where these structures were laterally displaced, still in laterodorsal position but more lateral than the laterodorsal sensory spots. Segment 4 with middorsal elevation as on the preceding segments (Fig. 5B). Unpaired seta in paradorsal position, and paired setae in subdorsal, lateroventral and ventromedial positions; subdorsal setae flanked by the two pairs of subdorsal sensory spots, ventromedial setae more mesial than those of female segment 2 (Figs. 5A–B, 7C, 8D). Sensory spots in paradorsal (one pair), subdorsal (two pairs), laterodorsal (one pair) and ventromedial (one pair) positions (Figs. 5A–B, 7C, 8D). Segment 5 with middorsal elevation as on the preceding segments (Figs. 5B, 7F). Paired setae in laterodorsal, ventrolateral and ventromedial positions; ventromedial setae more lateral than those of segment 4 (not aligned longitudinally) (Figs. 5A–B, 7E–F, 8D). Sensory spots in paradorsal (one pair), subdorsal (two pairs), laterodorsal (one pair) and ventromedial (one pair) positions (Figs. 5A–B, 7E–F, 8D); the latter pair aligned with that of segment 3. Intraspecific variation in the arrangement of the laterodorsal setae has been observed in a single specimen, where these structures were laterally displaced, still in laterodorsal position but more lateral than the laterodorsal sensory spots. Segment 6 with middorsal elevation as on the preceding segments (Figs. 5B, 7H). Unpaired seta in paradorsal position, and paired setae in subdorsal, lateroventral and ventromedial positions (the former flanked by the subdorsal sensory spots, the latter longitudinally aligned with those of segment 4) (Figs. 5A–B, 7H); deviations from the bilateral symmetry in the position of the ventromedial setae has been observed in a single specimen that had one seta mesially displaced, though still in ventromedial position. Sensory spots in paradorsal (one pair), subdorsal (two pairs), laterodorsal (one pair) and ventromedial (one pair) positions (Figs. 5A–B, 7H); the latter pair aligned with that of segment 4. Segment 7 without middorsal process or elevation. Paired setae in laterodorsal and ventromedial positions, the laterodorsal ones more lateral than the laterodorsal sensory spots, and the ventromedial ones aligned with those of segment 5 and female segment 2 (Figs. 5A–B, 7H). Sensory spots in subdorsal (two pairs), laterodorsal (one pair) and ventromedial (one pair) positions (Figs. 5A–B, 7H); the latter pair aligned with that of segment 3. Intraspecific variation in the arrangement of the laterodorsal setae has been observed in a single specimen, where these structures were mesially displaced, still in laterodorsal position but more mesial than the laterodorsal sensory spots. Segment 8 without middorsal process or elevation. Paired setae in subdorsal, lateroventral and paraventral positions; the former flanked by the subdorsal sensory spots (Figs. 5A–B, 7G, 8E). Deviations from the bilateral pattern in the arrangement of the paraventral setae has been observed in a single specimen, which had the left sternal plate with the seta in ventromedial instead of paraventral position. Sensory spots in subdorsal (three pairs), laterodorsal (one pair) and ventromedial (one pair) positions (Figs. 5A–B, 7G, 8E); the latter pair aligned with that of the preceding segment. Segment 9 without middorsal process or elevation. Paired setae in laterodorsal and ventromedial position; the latter longitudinally aligned with those of segments 5 and 7 (Figs. 5A–B, 7I–J, 8E). Sensory spots in subdorsal (three pairs), laterodorsal (one pair), ventrolateral (one pair) and ventromedial positions (Figs. 5A–B, 7I–J, 8E, H). Nephridia externally opening as short cuticular tubes with fringed tips (Fig. 5A). Segment 10 without middorsal process or elevation. Tergal plates with elongated, dagger-like projections at midlateral posterior margins (Figs. 5A–B, D, 6A–B, J, 8A, F). Two pairs of setae in lateroventral position (Figs. 5A–B, D, 8F). One pair of sensory spots in subdorsal, laterodorsal, ventrolateral and ventromedial positions (Figs. 5A–B, D, 8F). Segment 11 with one pair of type 3 sensory spots in subdorsal position (Figs. 5B, 7K). Males with two pairs of sexually dimorphic penile spines and genital pores (Figs. 5A, 8F). Lateral terminal spines absent; minute, rectangular, distally rounded, bulbous protuberances emerge between tergal and sternal plates, in males superficially covered by hairs (Figs. 5A, D, 7K).