Pycnocraspedum armatum Gosline, 1954

Schwarzhans, Werner W., Psomadakis, Peter N. & Nielsen, Jørgen G., 2025, Revision of the bathydemersal fish genus Pycnocraspedum (Ophidiidae; Teleostei), with description of two new species, Zootaxa 5636 (3), pp. 443-472 : 455-458

Pycnocraspedum armatum Gosline, 1954

Figures 1 , 2 , 3 , 5 , 7 , 12 ; Tables 1, 2

Pycnocraspedum armatum Gosline, 1954: 80–81 , tables 1–2, figs. 2e, 3e, off the Mauna Loa lava flow, Kona coast, Hawaii. Pycnocraspedum armatum Gosline, 1954 : Gosline & Brock (1960), Cohen & Nielsen (1978), Machida in Okamura & Kitajima

(1984), Chave & Mundy (1994), Nielsen et al. (1999), Mundy (2005), Prokofiev (2005), Evseenko & Okyama (2006),?

Prokofiev (2022), Girard et al. (2023). Pycnocraspedum squamipinne (non Alcock, 1889): Nielsen (1997), Fricke et al. (2011).

Material examined (14 specimens, 77.5–334 mm SL): specimens originally identified as P. microlepis : 1 specimen BSKU 5055, 234 mm SL, Mimase Fish Market, Kochi City , Kochi Prefecture, Shikoku Island, Japan, bottom trawl, 27 December 1955 ; 1 specimen BSKU 38643, 245 mm SL, Mimase Fish Market, Kochi City , Kochi Prefecture, Shikoku Island, Japan, bottom trawl, 14 March 1983 ; specimens originally identified as P. armatum : 2 specimens LACM 44837-1 , 213– 334 mm SL, RV Townsend Cromwell , st. 52–64 (off Hawaii), 16 November 1989; holotype of P. armatum USNM 162717, 310 mm SL, off Kona Coast of Hawaii , about 1/ 2 mile off shore from point of entry into sea of the 1950 lava flow, 2 June 1950 ; 1 specimen USNM 227389 , 77.5 mm SL, 21.035°N 156.797°W (off Molokai, Hawaii), RV Townsend Cromwell, st. 40–67, 41 ft shrimp trawl, 199–233 m, 19 November 1968 ; 1 specimen USNM 227390, 134 mm SL, 20.98°N 156.758°W (off Maui, Hawaii), RV Townsend Cromwell, st. 35-1, 41 ft shrimp trawl, 205–209 m, 27 March 1968 ; 1 specimen USNM 227406, 243 mm SL, 21.0633°N 156.518°W (off Maui, Hawaii), RV Townsend Cromwell, st. 40–92, 41 ft shrimp trawl, 274–318 m, 25 November 1968 ; 1 specimen USNM 227408, 191 mm SL, 20.6617°N 156.684°W (off Lanai, Hawaii), RV Townsend Cromwell, st. 33– 38, 70 ft shrimp trawl, 289–296 m, 9 November 1967 ; 2 specimens USNM 227412 , 225 and 265+ mm SL, 21.53°N 158.38°W (off Hawaii), RV Townsend Cromwell , cruise 54, st. 8, 229– 247 m, 24 September 1972 ; 1 specimen USNM 455317, 165 mm SL, 21.0108°N 156.759°W (off Maui, Hawaii), RV Townsend Cromwell , st. 40–49, 41 ft shrimp trawl, 218 m, 17 November 1968 ; 1 specimen USNM 455319, 276 mm SL, 20.99°N 156.751°W (off Maui, Hawaii), RV Townsend Cromwell, st. 35-2, 41 ft shrimp trawl, 201–216 m, 28 March 1968 ; specimens identified as P. squamipinne : 1 specimen MNHN 1994-0762 , 99 mm SL, 22°10'58.8''S 167°15'0''E (off New Caledonia), Biocal , st. cp109, 495– 515 m, 9 September 1985 .

Diagnosis. Precaudal vertebrae 11–14, total vertebrae 52–59; dorsal-fin rays 95–103; anal-fin rays 71–79; pectoral-fin rays 25–26; long gill rakers on first gill arch 4–5; pseudobranchials 4–7; 2–5 dorsal-fin rays in front of first vertebra; HL 23.8–26.9% of SL; body depth at vent 19.4–23.3% of SL; predorsal length 17–22.4% of SL; rear margin of preopercle with 4 spines and fleshy flap between spines 2 and 3; transversal scale rows above origin of anal fin 60–68, and above lateral line 15–20; otoliths> 15 mm in length: OL:OH = 1.95–2.2, dorsal rim crenulated or undulating.

Description. Relatively robust fish with stout tapering tail and rounded snout. Maximal size of fishes investigated 334 mm SL. Preopercular rim with 4 spines, 2 spines positioned at bend and 2 further up, with fleshy flap in between.

Meristics (14 specimens, including holotype of P. armatum ): precaudal vertebrae 13 (11–14); total vertebrae 56 (52–59); dorsal-fin rays 98 (95–103); anal-fin rays 71 (71–79); pectoral-fin rays 26 (25–26); caudal-fin rays 10; D/V = -3 (-2– -5); D/A = 29 (23–31); V/A = 17 (15–17); long gill rakers on first gill arch 5 (4–5); pseudobranchial filaments 5 (4–7); transversal scale rows above origin of anal fin 60–68, and above lateral line 20 (15–20); pyloric coeca 12 (12–16).

Morphometrics (4– 14 specimens) in % of SL: HL 24.6 (23.8–26.9); body depth at vent 22.7 (19.4–23.3); diameter of eye 4.4 (3.9–4.8); upper jaw length 13.4 (11.8–15); interorbital width 7.7 (6.1–7.7); pelvic-fin base to anal-fin base 21.2 (21.1–28); predorsal length 18.4 (17–22.4); preanal length 46.3 (40–48); prepelvic length 21.2 (19.3–23.3); pectoral-fin length 16 (16–18.1); pelvic-fin length 17.5.

Otolith morphology (4 specimens). Size up to 18 mm in length; OL:OH = 1.95–2.2 in specimens larger than 15 mm in length, 1.6 in specimens smaller than 7 mm in length; OH:OT = 2.3–2.9. Moderately thin, oval, elongated, anteriorly moderately projecting, posteriorly distinctly pointed, anterior and posterior tips inferior. Dorsal rim regularly curved, more or less strongly crenulated, undulating in largest specimen; ventral rim shallower and smoother than dorsal rim. Ornamentation of rims decreasing with size. Inner face moderately bent in horizontal direction, and slightly bent in vertical direction, with long, undivided sulcus reaching moderately close to anterior and posterior rims of otolith. Sulcus with shallow, undivided, uniform colliculum with flat to slightly concave dorsal rim and slightly convex ventral rim and rounded anterior and posterior tips. OL:CL = 1.3–1.45. Dorsal field with narrow, indistinct depression; ventral field smooth. Outer face less convex than inner face, smooth in large specimens, with many radial furrows and central tubercles in small specimens.

Coloration. Live coloration dark brown, sometimes light, speckled ( HURL 2019). Color of preserved specimens light brown.

Discussion. Specimens studied from BSKU (5055 and 38643) originally identified as P. microlepis from the Mimase fish market in Kochi, were probably trawled in Tosa Bay, which is not far from the type locality of P. microlepis given as east of Kii Peninsula. The two specimens from BSKU match Matsubara’s description (1943) of the unique holotype reasonably well in many aspects except for the number of pseudobranchial filaments (absent in the holotype according to Matsubara vs. 5–6 in the BSKU specimens) and pyloric coeca (20 vs. 13 in the BSKU 38643 specimen). Matsubara’s description is very detailed, and therefore we consider the two specimens in question from BSKU to represent P. armatum rather than P. microlepis . The nature of P. microlepis thus remains elusive.

Gosline (1954) described P. armatum from off Hawaii based on fishes killed by the eruption of Mauna Loa in 1950. He compared P. armatum to the type species P. squamipinne but not to P. microlepis , which was originally described as Itatius microlepis . The description of the unique holotype did not contain meristics and it is difficult to assess morphometric data based on the drawing. Pseudobranchial filaments were not mentioned for P. armatum but were mentioned in the description of the genus as ‘rudimentary’. A restudy of the holotype as well as multiple subsequently collected specimens of Pycnocraspedum from the Hawaiian Islands in the collections of LACM and USNM revealed a good match with the specimens from Japan (BSKU). Machida (1984) listed a difference of pyloric caeca of 12 for P. armatum and 20 for P. microlepis and 4 preopercular spines in P. armatum (vs. 2 in P. microlepis ) based on the original descriptions. The specimens BSKU 5055 and 38643 from Japan have 5 to 6 pseudobranchial filaments and the specimen BSKU 38643 has 13 pyloric coeca (information provided by N. Nakayama). Therefore, we consider P. microlepis ( Matsubara, 1943) as a nominally valid species distinct from P. armatum Gosline, 1954 and place the two specimens from BSKU with P. armatum .

Pycnocraspedum armatum is distinguished from its congeners by the higher number of dorsal-fin rays (95–103 vs. <93) except P. phyllosoma . Anal-fin rays also tend to be higher in number in P. armatum and P. phyllosoma (70–79 vs. 57–71). The dorsal-fin origin has a more anterior position in P. armatum compared to the other species with 2 to 5 fin rays before of the first vertebra (vs. 0 to 3 in other species) and a predorsal length of 17–22.4, mostly <21. Otoliths> 15 mm in length of P. armatum and P. phyllosoma are more compressed than in P. africanum and P. squamipinne (OL:OH = 1.95–2.2 vs. 2.4–2.7). The distinction of P. armatum from P. phyllosoma is relatively subtle despite their wide geographic separation (see below) and confined to differences in the number of transversal scale rows (60–68 vs. 72–75), scale rows above the lateral line (15–20 vs. 20–21) and spines on the preopercle (4 vs. 3).

Distribution. Pycnocraspedum armatum appears to be widely distributed from Japan to Hawaii and southward to New Caledonia, and possibly Central West Pacific according to HURL (2019).

Figures

FIGURE 1. Radiograph figures of selected specimens of the genus Pycnocraspedum to visualize position of dorsal-fin rays in relation to first vertebra; “1” denotes the first dorsal-fin ray above the first vertebra; numbers with negative denotation represent dorsal-fin rays in front of the first vertebra. 1A) Pycnocraspedum armatum, USNM 227390; 1B) Pycnocraspedum phyllosoma USNM 227413; 1C) Pycnocraspedum squamipinne, ZMUC P771871; 1D) Pycnocraspedum fulvum (holotype), BSKU 27497.

FIGURE 2. Gill rakers, pseudobranchial filaments and dentition details. 2A) Extracted first gill arch from Pycnocraspedum squamipinne, ZMUC P771871; 2B, 2E) Dentition of premaxilla, vomer and palatines of Pycnocraspedum armatum, USNM 227412, 2E is close-up to show sandpaper like texture of granular teeth; 2C–2D) Pseudobranchial filaments in Pycnocraspedum armatum, USNM 227412.

FIGURE 3. Detail figures and drawings of preopercular spines and lower preopercular pores in Pycnocraspedum; preopercular spines are numbered from 1 through 4 from the lower angle of the preoperculum upwards; abbreviation lpp = lower preopercular pore. 3A–3B) Pycnocraspedum armatum, USNM 227412, 3A1-3A2 specimen 1 left side, 3A3 specimen 1 right side (mirror imaged), 3B specimen 2; 3C–3D) Pycnocraspedum phyllosoma, 3C USNM 421587, 3D USNM 421586; 3E) Pycnocraspedum fulvum (holotype), BSKU 27497; 3F–3G) Pycnocraspedum africanum sp. nov., 3F holotype, MNHN 2000-5691, 3G paratype, MNHN 2000-5692; 3H) Pycnocraspedum rowleyensis sp. nov., holotype, WAM I.28059.021; 3I–3K) Pycnocraspedum squamipinne, 3I lectotype, BMNH 1890.7.31.1, 3J ZMUC P771871, 3K ZMUC P771737.

FIGURE 5. Otoliths, inner faces (if not noted otherwise) shown from right side. 5A–5C) Pycnocraspedum africanum sp. nov., 5A holotype, MNHN 2000-5691 (5A2 dorsal view), 5B paratype MNHN 2000-5692, 5C tentatively assigned specimen, IRSNB (5C2 dorsal view, 5C3 anterior view); 5D–5E) Pycnocraspedum armatum, 5D USNM 227412 (5D2 ventral view), 5E USNM 227390 (5E2 ventral view); 5F) Pycnocraspedum fulvum (holotype), BSKU 27497 (5F2 ventral view, 5F3 anterior view); 5G) Pycnocraspedum rowleyensis sp. nov., holotype, WAM I.28059.021 (5G2 ventral view); 5H) Pycnocraspedum phyllosoma, USNM 421587 (5H2 ventral view, 5H3 anterior view); 5I–5K) Pycnocraspedum squamipinne, 5I lectotype, BMNH 1890.7.31.1 (5I2 ventral view), 5J ZMUC P771871, 5L ZMUC P771739 (5L2 ventral view), 5K ZMUC P771738 (5K2 ventral view); 5M) †Pycnocraspedum cetonaense (holotype) SMF P.5694 (5M2 dorsal view, 5M3 anterior view).

FIGURE 7. Pycnocraspedum armatum Gosline, 1954; 7A, 7C) USNM 227412, 225 mm SL, 21.53°N 158.38°W, 229–247 m; 7B) radiograph of holotype, USNM 162717, 310 mm SL, off Kona coast, Hawaii.

FIGURE 12. Geographic distribution of the species of Pycnocraspedum. One symbol can represent more than one location.