Pterocryptis vorax, Ng & Kahar & Tan, 2025

Pterocryptis vorax , new species

Figs. 1 View FIGURE 1 , 2a View FIGURE 2 , 3a–b View FIGURE 3

Silurichthys hasselti View in CoL (non Bleeker, 1858): Choy & Chin, 1994: 769; Kottelat & Lim, 1995: 241 (in part).

Pterocryptis furnessi View in CoL (non Fowler, 1905): Kottelat & Lim, 1995: 241 (in part); Ng & Tan, 2004: 5; Ng et al., 2018: 133 (in part); Sulaiman et al., 2018: 33 View Cited Treatment .

Holotype. ZRC 49210 View Materials , male, 129.0 mm SL, Borneo: Brunei Darussalam, Temburong District, Sungai Temburong drainage, Sungai Belalong sub-drainage , Sungai Mata Ikan , downstream of Kuala Belalong Field Studies Centre , 4°32'50"N 115°9'28"E, coll. H. H. Tan & K.K. P. Lim, 6–9 October 2001. GoogleMaps

Paratypes. UBDM 1.00314 , 4 males, 126.0–147.0 mm SL, 1 female, 134.0 mm SL, Borneo: Brunei Darussalam, Temburong District, Sungai Apan at Outward Bound Batang Duri ( tributary of Sungai Temburong ), 4°33'42"N 115°9'01"E, coll. R. Kahar & J. Tony, 24 September 2020 GoogleMaps ; ZRC 51192 View Materials , 1 male, 84.6 mm SL, 1 female, 104.5 mm SL, Borneo: Brunei Darussalam, Temburong District, Sungai Temburong drainage, Sungai Dabai , about 1–2 km upstream from confluence of Sungai Belalong and Sungai Temburong , 4°33'18"N 115°9'43"E, coll. H. H. Tan & K.K.P. Lim, 5 October 2001 GoogleMaps ; ZRC 51194 View Materials , 3 males, 103.0– 150.6 mm SL, 6 females, 66.3–111.0 mm SL, data as for holotype GoogleMaps ; ZRC 66621 View Materials , 4 females, 83.1–140.9 mm SL, Borneo: Brunei Darussalam, Temburong District, Sungai Temburong drainage, Sungai Belalong sub-drainage , Sungai Mata Ikan , downstream of Kuala Belalong Field Studies Centre , 4°32'50"N 115°9'30"E, coll. H. H. Tan et al., 9 October 2023 GoogleMaps ; ZRC 51193 View Materials , 1 female, 120.2 mm SL, Borneo: Brunei Darussalam, Temburong District, Sungai Temburong drainage, Sungai Belalong sub-drainage , Sungai Esu , about 15 minutes upstream of Kuala Belalong Field Studies Centre , 4°32'18"N 115°9'35"E, coll. H. H. Tan & K.K.P. Lim, 6 October 2001 GoogleMaps .

Diagnosis. Pterocryptis vorax is distinguished from all congeners in having a wider gape (posterior margin of rictal lobe extending beyond vertical from posterior margin of orbit, vs. to vertical from posterior martin of orbit in P. berdmorei and P. furnessi or not reaching posterior margin of orbit in all other congeners; Fig. 2 View FIGURE 2 ), and from all congeners except its other Bornean congener, P. furnessi (known from the Kemena River drainage eastwards to the Baram River drainage in Sarawak), in having a highly contrasting (mottled/reticulated) color pattern on the flanks (vs. uniform brown color or an almost indiscernible reticulate pattern), dark vertical band at the caudal-fin base (vs. absent), a deeper caudal peduncle (8.2–10.4% SL vs. 5.1–8.4), and 48–49 (vs. 50–60) vertebrae. It also differs from all congeners except P. buccata and P. cucphuongensis in having fewer anal-fin rays (46–57 vs. 56–85). Pterocryptis vorax further differs from P. furnessi in having a deeper lower jaw with a more gently curved anteroventral margin ( Fig. 2 View FIGURE 2 ), and densely distributed dark brown patches on the flanks that coalesce to form a reticulate pattern (vs. widely scattered dark brown patches that do not coalesce to form a reticulate pattern; Fig. 3 View FIGURE 3 ).

Description. Morphometric and summarized meristic data are given in Table 1 View TABLE 1 . Body subcylindrical in preanal region, laterally compressed posteriorly, maximum body depth located immediately anterior to anal-fin origin. Head moderately depressed. Dorsal profile straight, descending gently from dorsal-fin origin to snout tip. Anterior profile of snout rounded. Anterior pair of nostrils tubular and anteromedial to maxillary barbel base. Posterior pair of nostrils bordered by fleshy dorsal and ventral membranes, separated from anterior nostrils by approximately eye diameter and situated posteromedial to maxillary barbel base. Eyes small, subcutaneous; located in anterior half of head; visible dorsally, but not ventrally.

Mouth subterminal; gape horizontal. Lower lip thin and papillose; upper lip slightly thicker, broken into irregular plicae that may separate posteriorly into small papillae. Well-developed rictal fold present, consisting of large and fleshy upper lobe joined at corner of mouth with lower lobe posterior to vertical through posterior orbital margin; lower lobe subtended by short submandibular groove. Poorly-developed supralabial fold present, extending from posterodorsal corner of upper rictal lobe to vertical through one half eye diameter posterior to posterior orbital margin.

Teeth villiform. Dentary teeth in slightly curved, elongate bands narrowing posteriorly, reaching from symphysis almost to mouth corners; premaxillary teeth in broader, slightly curved rectangular bands; vomerine teeth in two distinctly separate ovoid patches.

Laterosensory pores on dorsal and lateral surfaces of head visible as unpigmented spots, Temporal sensory canal with two pores: anterior pore just anterior to vertical at posteriormost extremity of opercular flap edge and just dorsal to horizontal at posterior pore; posterior pore just posterior to vertical at posteriormost extremity of opercular flap and just dorsal to horizontal at hyomandibula-opercle facet. Supraorbital sensory canal with six pores: epiphyseal pore on top of head, slightly posterior to vertical through middle of eye; parietal pore little over one eye diameter posterior to epiphyseal pore; four pores from nasal bone: two immediately anteromedial and posteromedial, respectively, to anterior nostril and two immediately posterior and anterior, respectively, to posterior nostril. Infraorbital sensory canal usually with five pores, rarely four; anterior pore medial to maxillary barbel base; additional pore may be present posterior to eye. Preoperculomandibular sensory canal with nine pores: one immediately posterior to hyomandibula-opercle facet, four along posteroventral margins of opercle and interopercle, one lateral to inner mandibular barbel base, three along lower jaw. Symphyseal pore absent. Lateral line complete, extending to middle of caudal-fin base; minute branches visible, directed posteroventrally, and decreasing in number posteriorly. Lateral line canal ossicles not visible externally.

Maxillary barbels slightly flattened, reaching to base of first anal-fin ray. One pair of mandibular barbels present; located slightly anterolateral to gular fold; barbels flattened for most of length, reaching to base of last pectoral-fin ray.

Gill membranes separate and overlapping, free from isthmus. Gular fold well developed and broadly curved. Branchiostegal rays 10 (17). Gill rakers short, without odontodes; anteriormost rakers on lower first arch small and widely spaced; 1 + 4 (1) or 1 + 6* (1).

Distal margin of dorsal fin pointed, with i,2 (3) or i,2,i* (14) rays; segments of first ray not co-ossified to form spine. Distal margin of pectoral fin broadly convex, with 9,i (9) or 10,i* (8) rays and third branched ray longest. Adpressed pectoral fin reaching to vertical through middle of dorsal-fin base. Segments of the proximal two-thirds of first pectoral-fin element co-ossified, forming spine. Pectoral spine and articulated segments sexually dimorphic in mature individuals. Spine in males broad and somewhat flattened dorsoventrally, with 3–9 (4 in holotype) serrations on posterior edge, increasing in size distally; proximal articulated segments with 0–1 (0 in holotype) serrations on posterior edge. Spine in females or juveniles slender, without serrations on posterior edges of spine proper and proximal articulated segments. Distal margin of pelvic fin convex, with i,7,i (17) rays and third or fourth branched ray longest. Distal margin of anal fin straight, with iii,42,i (1), ii,46,i (3), iii,45,i (2), iii,46 (1), ii,48* (1), iii,46,i (1), ii,48,i (1), ii,49 (1), iv,46,i (1), ii,49,i (1), ii,50,i (1), iii,49,i (1), iii,50 (1), or ii,54,i (1) rays; posterior end of anal fin rounded, joined to caudal fin for length of last anal-fin ray, with two fins separated by a small notch. Integument over anal fin thickened proximally for slightly more than half of ray lengths; fin-ray erector muscles extending along anterior edges of anal-fin rays, ventralmost extent of muscles that of thickened integument. Caudal fin weakly emarginate; upper lobe slightly longer than lower lobe and principal rays i,6,7,i (17). Procurrent rays 4–6 (6 in holotype) in upper lobe and 3 in lower lobe.

Urogenital papillae of both sexes located immediately posterior to anus. Papilla of males with a pointed tip of and those of females with a rounded tip.

Vertebrae 13 + 35 = 48 (2), 14 + 34 = 48* (7), 13 + 36 = 49 (1), 14 + 35 = 49 (5) or 15 + 34 = 49 (2).

Coloration. Flanks and thickened integument over anal fin with irregular light and dark brown blotches forming dense reticulate pattern. Dorsum darker brown, but with reticulate pattern still visible. Belly and breast cream, with fainter, less distinct reticulate pattern. Males with a more contrasting reticulate pattern consisting of larger brown blotches less densely interconnected and females with a less contrasting reticulate pattern consisting of smaller brown blotches that are more densely interconnected.

Dorsal surfaces and sides of head brown, with darker blotches rarely present; anterior nostril tube and membranes of posterior nostril slightly darker. Melanophores less dense ventral to level of eye, with color of head grading to cream and fewer melanophores largely aggregated along lower jaw margin.

Maxillary barbel densely powdered with melanophores along entire length, imparting dusky appearance. Mandibular barbel cream, with scattered melanophores along entire length.

Pectoral-fin interradial membrane hyaline; fin rays lightly powdered with melanophores except for distal onefifth of ray lengths, imparting appearance of thin hyaline band along distal margin of fin. Pelvic fin with hyaline interradial membrane and melanophores dusting proximal three quarters of fin rays, with hyaline band along distal margin of fin. Dorsal-fin membrane hyaline; fin rays covered by dense melanophores. Anal-fin membrane hyaline, with fin rays ventral to thickened integument having irregular brown blotches. Caudal-fin membrane and rays powdered with melanophores so as to appear dusky, except for very thin hyaline band along distal margin; caudal base prominently marked by a broad, vertical dark band with convex anterior and posterior edges.

Distribution. Pterocryptis vorax is known from hillstream habitats in Ulu Temburong, Batu Apoi Forest Reserve and Kuala Belalong Field Studies Centre, in Temburong District, Brunei Darussalam (all of which are located within the Temburong River drainage; Fig. 4 View FIGURE 4 ).

Habitat and ecology. Pterocryptis vorax inhabits streams with clear and fast-flowing water over a rocky and sandy substrate, sometimes with bedrock splitting the stratum and forming small cascades ( Fig. 5 View FIGURE 5 ). Other fish species typically associated with such habitats include: Hampala bimaculata , Paracrossochilus acerus , Tor tambra ( Cyprinidae ), Nematabramis steindachnerii , Rasbora agyrotaenia ( Danionidae ), Gastromyzon lepidogaster , Neogastromyzon brunei , Parhomaloptera microstoma , Protomyzon griswoldi ( Gastromyzontidae ), Pangio mariarum ( Cobitidae ), Hemibagrus baramensis ( Bagridae ), Ompok platyrhynchus ( Siluridae ) and Macrognathus maculatus ( Mastacembelidae ). Four of 17 individuals in the type series radiographed contained gastropods in the gut. These were identified as Clea sp. ( Nassariidae ), a common aquatic inhabitant of hillstream habitats in Borneo. The possibility that this is due to opportunistic feeding, or if P. vorax is truly molluscivorous remains to be studied.

Etymology. The specific epithet is the Latin adjective meaning “swallowing greedily” or “devouring”, in allusion to the wider gape of this species compared to P. furnessi , its other Bornean congener.