Pycnocraspedum squamipinne Alcock, 1889

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 : 465-467

Pycnocraspedum squamipinne Alcock, 1889

Figures 1 , 3 , 5 , 11 , 12 ; Tables 1, 2

Pycnocraspedum squamipinne Alcock, 1889: 386 ; figured in Alcock 1898: pl. 21, fig. 1 as Neobythites squamipinnis, Bay of Bengal, 20°17'30"N, 88°50'E, RV Investigator, depth 193 fathoms (353 m).

Pycnocraspedum squamipinne Alcock, 1889 : Menon & Yazdani (1968), Menon & Rama-Rao (1970), Menon & Rama-Rao (1975), Nielsen et al. (1999), Evseenko & Okiyama (2006), Psomadakis et al. (2020), Teena et al. (2021), Prokofiev (2022).

Material examined (6 specimens, 122–243 mm SL): 1 specimen lectotype, BMNH 1890.7 .31.1, 20°17'30"N 88°50'E ( Bay of Bengal ), RV Investigator, 353 m ; 1 specimen ZMUC P 771737, 226 mm SL, off Myanmar, Bay of Bengal , 18°16'N, 93°43'E, R / V Dr. Fridtjof Nansen, survey 2015404, st.19, bottom trawl, 127–130 m, 3 May 2015 ; 2 specimens ZMUC P 771736 and P 771738, 120– 195 mm SL, off Myanmar, Bay of Bengal , 18°14'N, 93°38'E, R / V Dr. Fridtjof Nansen, survey 2015404, St. 18, bottom trawl, 466–469 m, 3 May 2015 ; 1 specimen ZMUC P 771739, 225 mm SL, off Myanmar, Bay of Bengal , 16°26'N, 93°57'E, R / V Dr. Fridtjof Nansen, survey 2015404, st. 42, bottom trawl, 274–277 m, 6 May 2015 ; 1 specimen ZMUC P 771871, 196 mm SL, off Myanmar, Bay of Bengal , 16°26'N, 93°57'E, R / V Dr. Fridtjof Nansen, survey 2018411, st. 26, bottom trawl, 241– 229 m, 29 Aug. 2018 .

Diagnosis. Precaudal vertebrae 12–13, total vertebrae 47–51; dorsal-fin rays 90–92; anal-fin rays 57–65; pectoral-fin rays 25–30; long gill rakers on first gill arch 4; pseudobranchials 1–2; 1–3 dorsal-fin rays in front of first vertebra; HL 29.6–31.5% of SL; body depth at vent 17.3–18% of SL; predorsal length 25–29% of SL; transversal scale rows above origin of anal fin 52–58 (58–60 in paralectotypes according to Teena et al. 2021), and above lateral line 13–17 (11–15 in paralectotypes according to Teena et al. 2021); pyloric coeca 12–13; preopercle with 1 weak spine above first lower preopercular pore and broad concave section above; otoliths relatively small, at> 10 mm in length: OL:OH = 2.4–2.5, dorsal rim shallow, smooth.

Description. Relatively robust fish with stout tapering tail and rounded snout.Maximal size of fishes investigated 243 mm SL. Head stout, with straight, inclined dorsal profile. Preopercle with 1 weak spine above first lower preopercular pore, with broad concave section above and obtuse angle below second preopercular pore.

Meristics (6 specimens): precaudal vertebrae 12 (12–13); total vertebrae 49 (47–51); dorsal-fin rays 92 (90–92); anal-fin rays 65 (57–65); pectoral-fin rays 28 (25–30); caudal-fin rays 10; D/V = -2 (-1– -3); D/A = 24–31; V/A = 16–17; long gill rakers on first gill arch 4; pseudobranchial filaments 1 (1–2); transversal scale rows above origin of anal fin 52–58, and above lateral line 13–17; pyloric coeca 12–13.

Morphometrics (5 specimens) in % of SL: HL 29.6 (29.6–31.5); body depth at vent 17.3 (17–18); diameter of eye 4.9 (4.5–5.1); upper jaw length 15.4 (15.0–15.4); interorbital width 5.2 (5.2–6.2); pelvic-fin base to anal-fin base 26 (26–32.5); predorsal length 27 (25–29); preanal length 46–52; prepelvic length 20–21.5; pectoral-fin length 15.2 (15.2–18); pelvic-fin length 11.4–14.

Otolith morphology (3 specimens). Size up to 12 mm in length; OL:OH = 2.4–2.5 in specimens larger than 10 mm in length, 1.8 in specimens smaller than 6 mm in length; OH:OT = 2.6–2.8. Otolith relatively thin, elongated, anteriorly rounded, posteriorly rounded or slightly pointed; anterior and posterior tips along horizontal axis. Dorsal rim shallow, nearly flat or depressed at times, moderately lobed in small specimens; ventral rim shallow, regularly curved. All rims smooth. Inner face nearly flat, less bent than outer face. Sulcus moderately long, horizontal, with shallow, undivided, uniform colliculum with flat to straight dorsal rim and slightly convex ventral rim and rounded anterior and posterior tips. OL:CL = 1.5–1.6. Dorsal field without distinct depression; ventral field smooth. Outer face more convex than inner face, smooth.

Coloration. Live coloration unknown. Color of preserved specimens light brown.

Discussion. Teena et al. (2021) presented a re-description of P. squamipinne based on two of the three syntypes from the Bay of Bengal at ZSI (Kolkata) and 15 additional newly collected specimens off southern India. The values given for the syntypes (now paralectotypes) fall well into the range of the specimens studied by us, although they are larger at 270 and 277 mm SL than our specimens. The detailed figures of Teena et al. including the otolith of a 200 mm SL specimen match our descriptions reasonably well. However, the maximal range given by them for meristics and morphometrics in their table 1 exceeds all values that we recognized for P. squamipinne . Possibly, the maximum value refers to their largest specimen of 380 mm SL, which is also of an unusual size for this relatively small species. The cause for this discrepancy is unknown, but one possible explanation could be that the specimen(s) in question represent another species of the genus, for instance P. africanum . However, to resolve such speculation requires the review of the original specimens.

As analyzed here, P. squamipinne shows a number of characters that distinguish it well from its congeners. These are the low number of vertebrae (47–51 vs. 51–59), the low number of anal-fin rays (57–65 vs. 68–79, except 63 in P. fulvum ), the low number of pseudobranchial filaments (1–2 vs. 4–7), the low number of transversal scale rows (52–58) and scale rows above the lateral line (13–17), the large head (HL in % of SL = 29.6–31.5 vs. 22.7– 27.6), slender shape (body depth in % of SL = 17–18 vs. 18.9–23.3), and the predorsal length in % of SL (25–29 vs. 17–25). The rear margin of the preopercle is relatively thin and weak with only one distinct spine (the second from below as described in the chapter “Key characters”; Fig. 3 ). Also, the otolith morphology is distinctly different from that of its congeners being characterized by a shallow, nearly flat dorsal rim, the inner face less bent than the outer face (vs. inner face strongly or more bent than outer face) and a relatively short sulcus (OL:CL = 1.5–1.6 vs. 1.3–1.45). Furthermore, P. squamipinne does not seem to grow to the sizes of its congeners (maximal verified size is SL 277 mm SL vs. 345–420 mm SL).

Distribution. Pycnocraspedum squamipinne has been mentioned across a wide distribution range in the Indo-West Pacific from East Africa to New Caledonia. However, in our study we found that all records from outside of the Bay of Bengal represent different species: P. africanum in East Africa and mostly P. armatum elsewhere outside of the Bay of Bengal. It thus appears that P. squamipinne is endemic to the Bay of Bengal. Subject to review of certain specimens mentioned by Teena et al. (2021) it is possible that a second species of Pycnocraspedum may occur off India.

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 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 11. Pycnocraspedum squamipinne Alcock, 1889, lectotype, BMNH 1890.7.31.1, 20°17'30"N 88°50'E, 353 m.

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