Pycnocraspedum 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 : 449-450

Genus Pycnocraspedum Alcock, 1889

Pycnocraspedum Alcock, 1889 : type species by monotypy Pycnocraspedum squamipinne Alcock, 1889 .

Itatius Matsubara, 1943 : type species by monotypy Itatius microlepis Matsubara, 1943 .

Paragenypterus Schwarzhans, 1981 : type species by monotypy Brotulidarum centonaensis Schwarzans, 1978, a fossil otolith-based taxon.

Diagnosis (adopted and altered from Nielsen et al. 1999). A genus of the subfamily Neobythitinae characterized by the following combination of characters: Body short with large head; upper jaw ending behind eye; hind margin of preopercle with 1 to 4, spines; 2 median basibranchial tooth patches, sometimes accompanied by additional small single or pair of lateral patches; very small, closely packed teeth resembling sandpaper surface on dentary, premaxilla, vomer and palatines; 4 to 6 developed gill rakers on first gill arch; 2–3 lower preopercular pores; no upper preopercular pore; 1 to 7 small pseudobranchial filaments; pectoral-fin rays 24 to 28; precaudal vertebrae 11 to 14 (mostly 12 to 13); 0 to 5 dorsal-fin rays in front of first vertebra; otoliths slender with long, uniform sulcus. Head and body completely covered with small cycloid scales, including bases of dorsal, anal and pectoral fins.

General description: A number of characters occur in all species of Pycnocraspedum in the same manner. In order to reduce redundancy, the following description summarizes those characters that are valid in all the species here studied.

Head stout, with straight, inclined dorsal profile. Opercle with sharp, slightly extruding spine. Eye moderately small. Maxilla extending far behind eye, strongly widened posteriorly upward and downward from axis and with a vertical posterior end. Narrow, poorly defined supramaxilla. Pores: 1 anterior supraorbital, no posterior supraorbital, 3 anterior infraorbital, 3 posterior infraorbital, 3 anterior mandibular, 3 posterior mandibular, 2–3 lower preopercular. Head completely covered with scales, including opercle, preopercle, cheeks, and maxilla. Scales on head larger than scales on body and peduncle.

Dentition. Minute sandpaper-like granular teeth on broad dentary and premaxillary bands, narrow palatine bands, and a narrow, boomerang-shaped vomerine patch. Basibranchial tooth patches 2 long median and 1 small lateral patch on left or right side, rarely a symmetrical pair.

Discussion: Following the synonymization of the genera Tauredophidium Alcock, 1890 and Xyelacyba Cohen, 1961 with Acanthonus Günther, 1878 by Girard et al. (2024) and the establishment of Tenuicephalichthys Schwarzhans & Møller 2024, the subfamily Neobythitinae now comprises 37 genera. The interrelationships of many of the neobythitine genera have remained elusive. Matsubara (1943) found Itatius (syn. Pycnocraspedum ) resembling Neobythites , differing from Neobythites in: “1) bones of head soft; 2) pseudobranchiae absent; 3) developed gill-rakers on first gill-arch fewer than 5; 4) dorsal inserted above the upper angle of the gill-opening.” Gosline (1954) postulated the existence of a group of oviparous brotulid genera which he thought are intermediate between oviparous and viviparous genera and counted Pycnocraspedum and Volcanus (syn. Luciobrotula ) to this group. Cohen (1964) added Petrotyx to this group and Cohen & Nielsen (1978) considered Pycnocraspedum belonging to a cluster with Luciobrotula , Petrotyx and Spottobrotula . Machida (1984) found Pycnocraspedum resembling Neobythites . Studies using molecular phylogenetic analysis of neobythitine taxa so far are few. Møller et al. (2016) did not include Pycnocraspedum . Girard et al. (2023) resolved Pycnocraspedum as sister taxon of Neobythites . Wong & Chen (2024) showed Pycnocraspedum in a clade with Brotulataenia and Lamprogrammus .

A comparison of the diagnostic key characters of Pycnocraspedum —developed gill rakers, number of precaudal vertebrae, origin of dorsal fin, presence/absence of preopercular spines, number of pectoral-fin rays, and otolith morphology—showed the highest degree of congruence with Neobythites (except origin of dorsal fin) and Monomitopus (except origin of dorsal fin and developed gill rakers) ( Table 1 ). Particularly the origin of the dorsal fin in front of the first vertebra is an almost unique character within Ophidiiformes , shared only with Leptobrotula . The dorsal-fin commences above the first vertebra in some species of the genera Glyptophidium , Sirembo and Spottobrotula otherwise it commences above the third vertebra or posteriorly in other ophidiiforms. A low number of developed gill rakers on the first gill arch is shared with several other genera such as Barathrites , Dannevigia , Hoplobrotula , Luciobrotula , Petrotyx and Sirembo . Long, slender otoliths are also found in Bassogigas , Epetriodus , Luciobrotula , Monomitopus and Neobythites , but only in Bassogigas , Neobythites and in some species of Monomitopus the slender otolith shape is paired with a long sulcus. This comparison would indeed support a relationship of Pycnocraspedum with Neobythites as the most likely outcome.

Species: We consider all previously described 5 extant species as valid for Pycnocraspedum and describe 2 new species: P. africanum sp. nov. from the Western Indian Ocean, P. armatum Gosline, 1954 , widely distributed in the Western and Central Pacific as far east as to Hawaii and south to New Caledonia, P. fulvum Machida, 1984 from Japan, P. microlepis ( Matsubara, 1943) from Japan is considered nominally valid but could not be reassessed due to the apparent loss of the unique type, P. phyllosoma ( Parr, 1933) from the Caribbean, P. rowleyensis sp. nov. from off northwestern Australia, and the type species P. squamipinne Alcock, 1889 from the Bay of Bengal. In addition, there is one fossil otolith-based species from the Early Pliocene of Italy: P. centonaense ( Schwarzhans, 1978) .