Liljeborgia (Lilljeborgiella) scylla Timm, Stewart, Lörz & Horton, 2026, sp. nov.

Liljeborgia (Lilljeborgiella) scylla sp. nov. Figs 1, 2, 3, 4, 5, 6 Type material. Holotype: Pacific • Immature male, 7 mm, carcass and two slides; Clarion-Clipperton Zone; 12.045°N, 117.424°W, depth 4223 m; 01 / 03 / 2015; OMS contract area, “ RV Thompson ”, Cruise ABYSSLINE- 2, Station AB 2 - EB- 06; epibenthic sledge; SMF 62821; COI (PQ 734561). Type locality. Abyssal Pacific Ocean, Clarion-Clipperton Zone, 12.045°N, 117.424°W, depth 4223 m. Diagnosis. Maxilliped palp article one with dorsal distal setae, article three anterior margin with setae in groups or pairs. Palmar margin of gnathopod 2 of young males with prominent notch followed by triangular protrusion. Pereopods 3 and 4 propodus posterior border with long setae. Pereopods 5–7 bases very narrow, lacking crenulations on the posterior margin. Pleosomites 2 and 3 posterodorsal area produced into a tooth; epimera 1–3 rounded posterodistally. Uropod 1 peduncle dorsomedial margin with several spines. Telson shallowly cleft, 30 %, inter-teeth spine probably barely reaching tip of medial tooth. Eyes absent. Description. Based on holotype immature male, 7 mm, SMF 62821. Head (Figs 1, 2, 3): Rostrum small, reaching 25 % of article 1 of peduncle of A 1. Eyes absent, colourless in alcohol. Antenna 1 primary flagellum with 25 articles, with aesthetascs; accessory flagellum with 11 articles. Antenna 2 article four of peduncle with setae and with dorsomedial and ventrolateral spines; article five with dorsomedial setae; flagellum with 13 articles. Lower lip covered in fine setules. Upper lip rounded, not setose. Mouthparts (Figs 2, 3): Mandible right anterior margin with six triangular teeth, one of them large; left anterior margin with seven triangular teeth. Incisor process with five raker spines. Article one of palp length ~ 6.04 × width (ratio length article one / article two ~ 0.93); article two with setae along the distal margin, length ~ 5.44 × width; article three with nine setae along the margin and at the distal part of the margin, length 4.5 × width, 0.82 × article two. Maxilla 1 palp second article with two long setae on lateral margin, five slender spines on apical and medial margins and six slender facial setae; outer plate with ten robust spines, of which six are strongly denticulate; inner plate with a single seta on tip. Maxilla 2 setose, outer plate with two setae on anterolateral margin. Maxilliped inner plate with three anterior spines and five marginal and submarginal plumose setae; outer plate with nine evenly-spaced short, stout spines on medial border, interspersed with seven medioventral slender setae; palp article one with two distal and dorsal setae; article two with dorsomedial setae, with non-distal setae on outer margin; palp article three 0.8 × article two with two transverse rows of dorsomedial setae, one consisting of seven strong, plumose setae; dactylus 0.8 × article three, with anterior and posterior margins distinctly curved, posterior margin covered with fine setules, anterior margin with setae in groups or pairs. Pereon (Figs 4, 5, 6): Gnathopod 1 coxa broadly quadrate with anteroventral notch that is associated with a seta; merus with three groups of two to five setae; carpus with confluent groups of setae; carpus prolongation reaching just beyond palmar defining spine group; propodus twice as long as wide; palm border very slightly convex; with small, hooked spines and slender, long setae; dactylus without teeth. Gnathopod 2 coxa broadly rectangular; merus and carpus with groups of setae; merus with two solitary setae; carpus with confluent groups of setae; carpus prolongation almost reaching palmar defining spine group; propodus length 1.79 × width; palm border convex, with small hooked spines and slender, long setae; palmar margin with a prominent notch followed by triangular protrusion that appears to accept the dactylus; dactylus without teeth; G 2 larger than G 1; ratio length of propodus of Gn 2 / length of propodus of Gn 1: 1.4. Pereopod 3 coxa with one seta at anteroventral border; merus 1.59 × carpus and 1.41 × propodus; carpus length 5 × width; propodus length 8.78 × width; dactylus slender, slightly curved, medium length, 0.63 × carpus and 0.56 × propodus; propodus with long setae along posterior margin small spine distally. Pereopod 4 coxa with anteroventral notch with one seta; merus 1.76 × carpus and 1.52 × propodus; carpus length 4.5 × width; propodus length 6.64 × width; dactylus slender, slightly curved, medium length, 0.67 × carpus and 0.58 × propodus; propodus with long setae along posterior margin; anterior border with one small seta. Pereopod 5 coxa with very small posterior notch, basis very narrow (length 4.97 × width), posterior border completely smooth without teeth or crenulations; carpus 0.55 × merus; carpus and propodus 1.08 × merus; propodus with long setae along posterior margin; anterior border with one small seta. Pereopod 6 coxa with small posterior notch; basis very narrow (length 5.2 × width), posterior border completely smooth without teeth or crenulations; carpus 0.96 × merus; propodus with seven broken off spines or setae at the anterior border, three groups of setae with one to three setae on the posterior border and six setae at the tip; dactylus with short seta. Pereopod 7 coxa without posterior tooth; basis very narrow (length 3.8 × width), posterior border completely smooth without teeth or crenulations; ischium with two small setae; carpus 0.97 × merus; propodus of pereopod 7 double the length of propodus of pereopod 6, propodus with five spines on the posterior border and six groups of setae consisting of one to two setae on the anterior border. Pleosome (Fig. 1): Pleonite 1 posterodorsal area with no tooth; epimeron 1 rounded, with posterior border slightly convex. Pleonite 2 posterodorsal area produced into a tooth; epimeron 2 rounded, with posterior border slightly convex. Pleonite 3 posterodorsal area produced into a tooth; epimeron 3 rounded, with posterior border almost straight (very weakly convex). Urosome (Figs 2, 5, 6): Urosomite 1 with a distinct middorsal tooth; peduncle of uropod 1 with two dorsolateral spines and one spine distally; four dorsomedial spines; outer ramus lateral margin with five spines and no medial spines, one small spine at the tip of ramus; inner ramus lateral margin without spines and medial margin with four spines. Urosomite 2 with a distinct middorsal tooth; peduncle of uropod 2 with two dorsomedial spines; outer ramus lateral margin with three small spines; inner ramus medial margin with five spines. Urosomite 3 lacking middorsal tooth; outer ramus medial margin without spines, lateral margin with five setae; inner ramus with four spines on lateral margin and two spines on medial margin; lateral and medial margins of both rami microsetose. Telson cleft to 30 % of its length; outer tooth of each lobe overreaching medial tooth; inter-teeth spine broken off or damaged at both sides but probably barely reaching tip of medial tooth. Etymology. The name scylla is a reference to the Liljeborgia species described by Cedric d’Udekem d’Acoz and Wim Vader: Liljeborgia charybdis d’Udekem d’Acoz & Vader, 2009. There is a well-known idiom - to choose between Scylla and Charybdis which means “ to choose the lesser of two evils ” and we think that the genus Liljeborgia would be incomplete with only a “ Charybdis ” and no “ Scylla ”. Scylla, like Charybdis, is a sea monster from Greek mythology that lives by a rock in the strait between Sicily and Italy. Remarks. The new species belongs to the subgenus Lilljeborgiella (d’Udekem d’Acoz 2010 a): several spines are present on the dorsomedial margin of the peduncle of uropod 1; some or all of the setae on the anterior margin of article three of the maxilliped palp form groups or pairs, and the palp of article one possesses distal outer setae; the setae on the posterior border of the propodus of pereopods 3 and 4 are rather long and the basis of the pereopods 5–7 is not broad. Liljeborgia scylla sp. nov. is morphologically very similar to the abyssal amphipod species L. holthuisi but can be clearly distinguished from it (Table 1). The most significant difference between the two species is the stoutness of the basis of pereopod 7. The basis is significantly narrower in L. scylla than in L. holthuisi: ~ 3.8 × as long as wide in L. scylla sp. nov. and 2.58 × as long as wide in L. holthuisi. The new species has a middorsal tooth on pleonites 1–3, but in L. holthuisi, these teeth are followed by a rounded edge. The urosomite 1 has a distinct middorsal tooth in L. scylla sp. nov. and no carina, while the urosomite 1 has a middorsal carina with two very small teeth on each side in L. holthuisi. The gnathopod 2 of L. scylla sp. nov. has a distinctive deep notch on the palmar margin. Liljeborgia holthuisi also has a similar but smaller protrusion in the same position as in L. scylla sp. nov. The original description of L. holthuisi is based on a single male specimen of 10.5 mm length. By examining more individuals of these two species, we may reveal whether the palmar notch is a sexually dimorphic character and whether there is ontogenetic variation. Liljeborgia scylla sp. nov. and L. holthuisi also share their occurrence in the abyssal waters of the Pacific Ocean. Liljeborgia holthuisi was collected at depths of 5825–5841 m in the Peru-Chile Trench (d’Udekem d’Acoz 2010 b). The new species was collected ~ 4500 km away in the Clarion-Clipperton Zone at a depth of 4137 m. The species L. cota J. L. Barnard, 1962 is also similar in having a shallow cleft of the telson (34 %). The gnathopod 2 in L. cota also has a very similar protrusion and notch that is more prominent in juvenile males, while older males have a smooth palm. Additionally, the gnathopod 2 of L. cota has a dentate dactylus, compared to the smooth dactylus of L. scylla sp. nov. While both species inhabit the Northeast Pacific Ocean, their depth distributions di