Mystriophis caboverdensis Da Luz, Lopes, Jimenez & Psomadakis 2025, sp. nov.

Mystriophis caboverdensis Da Luz, Lopes, Jimenez & Psomadakis, sp. nov. urn:lsid:zoobank.org:act: 37740D65-0C8F-49E6-A518-F73DE487B370 New English name: Cabo Verde spoon-nose eel (Figs. 1–4, 6, Tables 1–3) Holotype. IEO1662, 723 mm TL, on the shelf between Boa Vista and Maio islands, Cabo Verde Archipelago, Eastern Central Atlantic Ocean (15°40’58.19”N, 23°01’10.81”W), R / V Dr. Fridtjof Nansen, Station 30, bottom trawl, 195 m depth, 30 November 2021. Diagnosis. The following combination of characters distinguishes Mystriophis caboverdensis sp. nov. from its congeners: dorsal-fin origin in front of pectoral-fin tip; inner and outer maxillary teeth subequal in size; head length 11.7 % of TL; snout length 16.1 % of HL (1.9 % of TL); interorbital width narrow, 6.8 % of HL (0.8 % of TL); predorsal length 13.7 % of TL; pectoral-fin length 22.9 % of HL (2.7 % of TL); distance between upper edge of gill opening and origin of dorsal fin 18.4 % of HL (2.1 % of TL); pectoral-fin rays 12; lateral-line pores to anus 64/63 (65/65 to anal-fin origin); vertebral formula 9–64–153; colouration dark brown with white streaks on the sides of head and distinct white spots along lower jaw and below eye; dorsal fin with wide black margin; surface sensory papillae on the nape, visible as a faint pale band crossing the head. Description. Morphometric and meristic data are presented in Table 1. Body moderately elongate, its depth 26.1 and 34.3 in TL at gill opening and anus, respectively. Branchial basket moderately expanded. Head and trunk shorter than tail; head and trunk 2.2, head 8.6, and tail 1.8 in TL. Head elongate and pointed, its dorsal and ventral profiles nearly straight (nape slightly convex); head ogive-shaped when viewed from above, its width 4.3 in HL. Snout short, blunt, laterally constricted near tip, overhanging beyond tip of lower jaw; snout subconical when viewed from above. Lower jaw included in upper jaw, its tip reaching beyond base of anterior nostril tube. Upper-jaw length 2.2 in head. Center of eye situated in anterior third of upper jaw. Lips well developed. Anterior nostril a short tube, laterally directed, inserted at deepest point of snout constriction (Fig. 2); posterior nostril opens along outer edge of upper lip, entirely covered by a flap whose center lies beneath anterior margin of eye. Eye relatively large, 10.6 in HL (Table 1), positioned dorso-laterally on head. Interorbital space flat and narrow, less than eye diameter. Median fins well developed, folding back into a deep dermal furrow, and ending about an eye diameter before the tail’s finless tip. Vertical through dorsal-fin origin slightly behind mid-pectoral fin length; Pectoral-fins moderate, oval in shape; upper edge of pectoral base inserted slightly above upper end of gill opening; the base lying posteroventrally at about 45° and ending well above upper half of gill opening. Gill opening crescent-shape, on lower half of body, slightly inclined backwards. Interbranchial distance about equal to unstretched gill opening. Cephalic pores (Fig. 3): SO 1+4; IO 3+3; POM 6+2 (7+2 on right side); STC 3; F 1. Surface sensory papillae well developed and contained within the white pigmented streaks and lines present on sides and top of head (see Fig. 5B). Lateral-line pores well-developed; 9 before gill opening in a high arching sequence, 64/63 before anus (pores not visible on posterior part of tail). Teeth conical, slightly recurved, quite robust, and unequal. Upper and lower jaw biserial, vomerine teeth uniserial. Intermaxillary (Fig. 3A) composed of 1 central and 3 fang-like teeth on each side at tip of snout (anteriormost central tooth and first 2 lateral teeth largest; the smaller lateral likely regenerating), followed a little farther back on the mesial line by a pair of smaller teeth placed in front of the first vomerine tooth. Vomerine teeth in a single row consisting of 2 widely separated, large fang-like teeth (the largest in the mouth) followed by 5 more closely set teeth (partially embedded by soft tissue), decreasing in size posteriorly (Fig. 3A). Maxillary with 38/36 and 28/30 teeth on inner and outer row, respectively; teeth on inner and outer rows subequal in size, the outer teeth more pointed and beginning at level of fifth (left) and third (right) inner tooth (4A). Dentary (Fig. 3B) with 37/34 and 26/22 teeth on inner and outer row, respectively; outer row much larger, consisting of 2/3 large, widely spaced teeth anteriorly (each preceded by a smaller replacement tooth on the left side) followed by 9/4 smaller, similar-size, closely-set teeth, these followed by 13/16 very small teeth progressively decreasing in size. The inner teeth beginning at level of third (left) and between the second and third (right) outer tooth (Fig. 3B). Fresh colouration (after defrosting). Nearly uniform dark brown, head and ventral side somewhat paler (Fig. 1); distinctive white oblique lines on sides of head: the first from corner of mouth onto cheek (to about mid-eye level), the second from the apical tip of the first line running posteriorly as a short dotted line (the two lines forming an angle <90°), the third as an irregular/dotted oblique line on the branchial region; distinct white spots or marks along lower jaw, on posterior nasal flap and posteroventral corner of eye (Fig. 4A); a faint pale dotted band on top of head at level of nape and a pair of white oblong patches diverging posteriorly on each side of ventral midline of throat and a single white patch, (overlain by pin point melanophores) at level of isthmus extending onto anterior part of abdomen (Fig. 4C); all white markings (i.e. spots, dotted lines and bands) associated to cephalic pores or surface sensory papillae; pattern of fine longitudinal wavy lines of darker tone forming the deep part of dermal folds on sides and top of head; supratemporal and anterior lateral-line pores white prominently encircled in dark brown (Fig. 4B); dorsal fin white basally, distal half black (Fig. 6); basal half of pectoral fin whitish, light brown on distal half (Fig. 4A); anal fin colour pattern mostly similar to dorsal fin. Colouration in preservative. Similar to fresh colouration but body lighter and white lines on the head less distinct. Size. Known from the holotype, a 72.3 cm TL adult female and a photographic record of a 100 cm specimen misidentified as Mystriophis rostellatus uploaded on FishBase www.fishbase.org (version 03/2025) by Pedro Niny Duarte. Etymology. Named for Cabo Verde, the type locality of the new species. Distribution (Fig. 5). Known from the holotype, collected by bottom trawl at 195 m depth in the southeastern part the Cabo Verde Archipelago (between Boa Vista and Maio Islands) and from a photographic record of a 100 cm TL specimen (see above) captured from Grande Islet, located in the southern part of the Cabo Verde Archipelago. Comparisons. Mystriophis caboverdensis sp. nov. is unique among Mystriophis species in having the dorsal-fin origin slightly behind mid-length of pectoral-fin (vs. above or behind pectoral-fin tip in M. rostellatus and M. crosnieri) (Figs. 1, 6, 7A, 8A, 11A). It is also distinguished from its congeners in having 153 total vertebrae (vs. 154–158 in M. rostellatus and 136–144 in M. crosnieri); 12/12 pectoral-fin rays (vs. 13 in M. rostellatus and 13–14 in M. crosnieri); 64/63 lateral-line pores before anus (vs. 55–58 in M. rostellatus and M. crosnieri); inner and outer row of maxillary teeth subequal in size (vs. teeth on outer row larger; see p. 208 in Blache 1971); predorsal length 117.4 % HL (vs. 123.9–135.3 % in M. rostellatus and 134.1–147.8% HL in M. crosnieri); distance between upper end of gill opening and origin of dorsal fin 18.4 % HL (vs. 23.9–35.3 % in M. rostellatus and 34.1–47.8 % in M. crosnieri). The new species is further distinguished from M. rostellatus in having a larger preanal length 45.8 % (vs. 40.4–44.3%) TL and eye diameter 9.4 % (vs. 6.7–8.7 %) HL and a greater width at isthmus 10.8 % (vs. 5.2–8.3 %) HL, as well as teeth tips ungrooved (vs. grooved; see fig. 3 in Blache 1971). Likewise, it is further distinguished from M. crosnieri in having a smaller HL 11.7 % (vs. 12.2–12.8 %) TL, snout length 16.1 % (vs 18.3–20.6 %) HL, interorbital width 6.8 % (vs. 8.7–11.8 %) HL and pectoral fin length 22.9 % (vs. 28.2–35.6 %) HL, body depth at anus 2.9 % (vs. 3.1–3.8 %) TL. Furthermore, based on comparisons with the M. crosnieri specimen examined by us, the new species has a narrower head (see Figs. 4B, 7C), its greatest width 2.7 (vs. 3.6 %) TL. In pigmentation, M. caboverdensis sp. nov. is distinguished from M. rostellatus and M. crosnieri in having an overall darker brown body when fresh (vs. dark ochre to light reddish brown) with white streaks and short dotted lines on the sides of head and distinct white spots along lower jaw and posteroventral corner of eye (vs. no white markings on head and body); dorsal fin with wide black margin (vs. dorsal fin with narrow black margin) (Fig. 6), also see Blache (1971: figs. 1, 6); sensory papillae on the nape individually undistinguishable, visible only as a faint pale band crossing the head (vs. sensory papillae on nape visible as a pale dotted-line crossing the nape with 2 shorter parallel branches running forward perpendicular to the main row) (Figs. 4B, 7C, 10A). The new species is further distinguished from M. rostellatus in having wavy longitudinal lines of darker tone (vs. lighter tone) forming the deep part of dermal folds on anterior part of body and from M. crosnieri in lacking yellowish tinge on top and sides of head (Figs. 6, 7, 8). Finally, M. caboverdensis sp. nov. is distinguished from Mystriophis sp. A (an undescribed species known from off Angola) in having a shorter predorsal length 13.7 % (vs. 24 %) TL and more total vertebrae 153 (vs. 141). Molecular analysis. The ML tree inferred from the COI sequences resolved into three major clades (Fig. 9A), largely with support bootstra