Peltorhamphus, Munroe, 2021

Munroe, Thomas A., 2021, Systematic revision of the flatfish genus Peltorhamphus Günther, 1862 (Teleostei: Pleuronectiformes: Rhombosoleidae), including description of a new species from Southeastern New Zealand, with biological and ecological summaries for the species, Zootaxa 4905 (1), pp. 1-104 : 70-82

Peltorhamphus sp. A.

Roberts et al. 2015:S178 (listed, checklist fishes of New Zealand).

Munroe 2015b:1698 (species account including colour photograph; size; diagnostic features; in key; brief summaries of biology, distribution and habitat; New Zealand).

Roberts et al. 2018:127 (listed, online checklist of fishes of New Zealand).

McMillan et al. 2019:249–250 (brief mention; size <200 mm TL; distinguished from P. latus and P. novaezeelandiae , respectively).

Diagnosis. Peltorhamphus kryptostomus n. sp. is distinguished from congeners by the combination of: a deep body, with greatest depth anterior to midpoint and with moderately rapid posterior taper; anterior profile of snout smoothly rounded; second ocular-side pectoral-fin ray filamentous and shorter than greatest body depth; 1–5 conspicuous, finger-like filaments on inner anteroventral margin of fleshy skinfold on ocular-side lower jaw; absence of scales on blind sides of dorsal- and anal-fin rays; relatively large eyes with well-developed pupillary operculum; relatively narrow interorbital space (usually <diameter of lower eye) with 2–4 scales; usually with 4–6 scales in diagonal row between anteroventral margin of lower (non-migrated) eye and dorsal margin of rostral flap above mouth; gillrakers on first arch long, pointed, robust, with first and sometimes second raker on upper limb overlapping dorsalmost raker(s) on lower limb of first arch); relatively low meristic values (37–38 total vertebrae, 86–97 dorsal- and 59–67 anal-fin rays, 64–82 lateral-line pores, usually 23–24 supracranial pterygiophores, 14–20 total gillrakers on first gill arch, 4–6 on upper limb of first arch); relatively large and wide head; wide caudal peduncle; light-brown to lightgray ocular-side background colouration with numerous, minute, pinkish spots over entire surface, and with many scales on ocular side of head and body with black pigment on bases of ctenii; dorsal and anal fins in both sexes with either a pattern of a single darkly pigmented ray alternating with 4–8 lighter-pigmented rays, or with rays uniformly pigmented; and with black pigmentation on inner lining of ocular-side opercle and entire roof of mouth.

Holotype ( Fig. 25 ). NMNZ P.046433; (75.8 mm SL, immature female); Otago Harbour, Aramoana Flats , 45º47.25’S, 170º41’E; 1 m; 05 Feb 2010.

Paratypes (measurements in mm SL in parentheses). NMNZ P.005412; (105.6); Canterbury, Akaroa , 43º50’S, 172º56’E; 30 Jun 1965 .

NMNZ P.051867; (113.0); Canterbury, Akaroa , 43º50’S, 172º56’E; 30 Jun 1965 .

NMNZ P.046453; (91.9); Otago, Oamaru Harbour , 45º06.35’S, 170º58.75’E; Jan 1965 .

NMNZ P.004292; (101.9); Otago, Blueskin Bay , Otago Peninsula , 45º43.28’S, 170º40.33’E; 20–22 m; 09 May 1990 .

MA125778 (formerly NMNZ P.046455); (74.6); Otago, Long Beach, Otago Peninsula , 45º45.18’S, 170º38.93’E; 2–5 m; 11 May 1990 .

NMNZ P.046434; (59.1); Otago Harbour, Aramoana Flats , 45º47.25’S, 170º41’E; 05 Feb 2010 .

NMNZ P.046436; (50.8); Otago Harbour, Aramoana Flats , 45º47.25’S, 170º41’E; 05 Feb 2010 .

NMNZ P.046439; (33.2); Otago Harbour, Aramoana Flats , 45º47.25’S, 170º41’E; 05 Feb 2010 .

USNM 427115 (formerly NMNZ P.046437); (56.1) ; Otago Harbour, Aramoana Flats , 45º47.25’S, 170º41’E; 05 Feb 2010 .

NMNZ P.046429; (132.0); Southland, between Waikawa Harbour and Chaslands Mistake, Caitlins, 46º40.55’S, 169º14.50’E; 40 m; 19 Mar 2010 .

(See also Non-type material under Material examined.)

Description. Meristic data summarized in Table 1. Values for holotype listed first and in bold here and in Table 1. Supracranial pterygiophores 23, range 21–26, usually 23–24 (60 of 74 individuals). Pterygiophores inserted into first interneural space 3, range 1–3, usually 2–3 (73 of 74 individuals). Pterygiophores inserted anterior to first haemal spine 9, range 6–11, usually 8–9 (55 of 74 individuals). Dorsal-fin rays 95, range 86–97, usually 88–97 (74 of 75 individuals). Anal-fin rays 62, range 59–67. Caudal-fin rays 18, range 17–20, usually 18 (69 of 74 individuals). Ocular-side pectoral-fin rays 9, range 7–11, usually 8–11 (62 of 64 individuals), rarely 7 (2 individuals). Blindside pectoral-fin rays 7, range 7–10, usually 8–9 (55 of 64 individuals). Ocular-side pelvic-fin rays 6 (74 of 74 individuals). Blind-side pelvic-fin rays 4, range 3–4, usually 4 (71 of 73 individuals). Abdominal vertebrae 10, range 9–11, usually 10 (71 of 75 individuals including holotype with 3+7 arrangement), rarely 9 (3 of 75 individuals with 3+6 abdominal vertebrae), or 11 (1 individual with 3+8 abdominal vertebrae). Caudal vertebrae 27, range 26–29, usually 27–28 (73 of 75 individuals). Total vertebrae 37, range 36–38, usually 37–38 (74 of 75 individuals), rarely 36 (1 individual). Finger-like filaments on inner anteroventral margin of fleshy skinfold on ocular-side lower jaw 3, range 0–4, usually 1–4 (57 of 63 individuals), rarely with 5 filaments (1 of 63 individuals), or without filaments (5 of 63 individuals; but see remarks below). Gillrakers on upper limb of first arch on blind side 4, range 4–6, usually 5 (46 of 64 individuals). Gillrakers on lower limb of first arch on blind side 11, range 10–14, usually 11–13 (58 of 64 individuals), rarely 10 or 14 (3 individuals each). Total gillrakers on first arch on blind side 15, range 14–20, usually 16–18 (53 of 64 individuals). Interorbital scales 3, range 2–4, usually 3 (43 of 63 individuals). Scales in diagonal row between anteroventral margin of lower (non-migrated) eye and dorsal margin of rostral flap above mouth 5, range 3–6, usually 4–5 (57 of 60 individuals). Scales between mid-dorsal margin of dorsal eye and dorsal margin of head 8, range 7–11, usually 8–10 (53 of 59 individuals). Lateral-line pores 78, range 64–82, usually 67–82 (52 of 53 individuals).

Morphometric data summarized in Table 12, compared with that of other species in Table 2 , discussed in further detail in the Morphometric variation section below, and plotted for select features in Figs. 27 A–J. Body oval ( Figs. 25–26 ), laterally compressed; with relatively short trunk (TKL 65.3–76.2% of SL, X = 71.8%); greatest body depth (BD 42.5–50.4% of SL, X = 46.7%) varying ontogenetically, larger fish having proportionally deeper bodies than smaller fish ( Fig. 27A ); greatest body depth in anterior one-third of body, usually equal with vertical through anterior third of ocular-side pectoral fin, and with moderately rapid posterior taper beyond this point, and with rather steep taper anterior to this point. Caudal peduncle very short, relatively wide (CPD 9.5–11.9% of SL, X = 10.7%). Head large, wide, rounded anteriorly or with blunt point on horizontal between eyes ( Figs. 25–26 ); dorsal profile of head above horizontal between eyes steeply convex to point about equal with vertical at posterior border of eyes, then rising more gradually to point about equal with posterior margin of opercle. Head relatively short (HL 26.1–32.5% of SL, X = 28.4%); proportionally smaller in smaller individuals ( Fig. 27B ); HL shorter than head width (HW 34.2–49.3% of SL, X = 44.2%); HW increasing slightly with increasing fish size ( Fig. 27C ); HW/HL = 1.2–1.8, X = 1.56. Head width dorsal to upper eye (DHW 25.0–43.4% of HL, X = 34.3%) moderately wide ( Figs. 25–26 ); DHW increasing slightly with increasing fish size ( Fig. 27E ); no secondary scales on primary scales above or just dorsoposterior to dorsal eye. Snout moderately long (SNL 27.8–33.6% of HL, X = 30.9%); SNL growth isometric relative to increasing HL ( Fig. 27F ); snout broadly rounded, or with blunt point on anterior profile and covered with strong, ctenoid scales; greatest length of snout at horizontal between eyes; about 8–10 scales between anterior margin of eyes and profile of snout. Ocular side of snout with conspicuous rostral flap whose dorsoposterior margin nearly surrounds and nearly conceals entire mouth, except for posteriormost end of jaws; rostral flap anteriorly with short, fleshy rostral hook (RHL14.2–30.3% of HL, X = 21.4%) covering tip of jaws anteriorly, and with posterior end extending ventrally to point about at vertical through posterior nasal sac. Ventroposterior section of rostral flap also with an inverted U-shaped vertical opening, exposing only posteriormost tips of jaws ventrally. Two ocular-side nostrils anterior to interorbital space, asymmetrically placed closer to dorsal margin of lower eye ( Fig. 5C ). Anterior ocular-side nostril a short tube with terminal, relatively long, membranous leaf-like flap reaching posterior nostril when depressed posteriorly, and with fleshy membrane at its base. Ocular-side posterior nostril a nearly vertical slit surrounded by thin membrane. Two blind-side nostrils; not conspicuous. Anterior blind-side nostril, located above anterior one-third of lower jaw, a short tube with delicate terminal flap; posterior blind-side nostril, located above midpoint of jaw, a horizontal slit surrounded by fleshy membrane. Eyes relatively large (ED 13.5–23.3% of HL, X = 18.6%); ED decreasing proportionally with increasing fish size ( Fig. 27G ); eyes elliptical, not contiguous; usually with anterior margins of eyes nearly equal in position, or with anterior margin of upper eye slightly in advance of anterior margin of lower eye; with conspicuous, well-developed pupillary operculum ( Fig. 2B ) in both juveniles and adults. Interorbital width relatively narrow (IO 5.6–11.2% of HL, X = 8.8%), ontogenetically variable ( Fig. 27H ) and increasing proportionally with increasing HL; IO usually <eye diameter at all sizes. Mouth moderate in size (UJL 24.1–33.3% of HL, X = 28.9%); UJL increasing proportionally with increasing HL ( Fig. 27I ); jaws asymmetrically developed towards blind side; all but posterior margin of jaws on ocular side nearly completely concealed by rostral flap; blind-side jaws straighter, only slightly decurved posteriorly. Diagonal distance between anteroventral margin of lower (non-migrated) eye and dorsal margin of rostral flap above mouth (EUM 9.3–18.4% of HL, X = 14.9%), relatively broad in all but the smallest individuals, increasing in size ontogenetically ( Fig. 27J ). Mouth opening on ocular side small, an inverted U-shape ( Fig. 28B ), opening at vertical through anterior base of ocular-side nostrils. Ocular-side lower lip smooth, without labial papillae. Teeth, present only on blind-side jaws, slender, villiform, in 2–4 irregular rows; teeth in anteriormost rows slightly larger than posterior teeth in same row. Fleshy skinfold on inner anteroventral margin of ocular-side lower jaw with 1–5 finger-like filaments ( Fig. 3A ). Postorbital length relatively long (POL 12.9–16.3% of SL, X = 14.4%), about 33–38% of HW. Upper head lobe (UHL 22.0–26.4% of SL, X = 24.7%) wider than lower head lobe (LHL 11.5–18.8% of SL, X = 15.1%).

Superficial neuromasts on blind side of head inconspicuous, but with visible lappets; neuromasts usually in consistent arrangement of three, more or less, parallel longitudinal rows dorsal to horizontal through nostrils, and with another series located just posterior to jaws. Dorsalmost row of neuromasts, located close to body margin, beginning on snout and extending posteriorly to about midpoint of head; middle longitudinal row of neuromasts beginning on anterior snout and extending posteriorly nearly to three-fourths of head length; ventralmost longitudinal row located in shallow groove beginning just posterior to nostrils and extending to about midpoint of head, with fewer, more closely spaced neuromasts than in other rows. Another series of neuromasts in curved row following contour of jaws; ventralmost neuromasts in this series located just ventral to posterior margin of jaws, with remaining neuromasts in this series more or less following ventral curvature of jaws nearly to distal tip of jaws. Several prominent free neuromasts on blind side of head situated dorsal and posterior to neuromast series located behind jaws, submarginally along ventral surface of opercle, and on ventral portion of lower jaw.

Gillrakers not toothed, present on both limbs of gill arches on ocular and blind sides. Gillrakers on upper limb of first blind-side gill arch robust and similar in shape and size to those on lower limb ( Fig. 12D ). Upper gillrakers on first blind-side arch long, cylindrical, with thickness uniform over most of their lengths; tips pointed, sometimes recurved; posteriormost gillraker of upper limb reaching ventrally to, or slightly beyond, dorsalmost gillraker on lower limb of same gill arch, or sometimes reaching tip of second dorsalmost gillraker on lower limb. Gillrakers on lower limb of first gill arch slightly longer than those on upper limb, except ventralmost 2–4 gillrakers on lower limb of first blind-side gill arch usually much smaller and more rounded than others on this limb. Posterior margin of operculum usually fringed with conspicuous, small, membranous flaps and short, thin, finger-like cirri.

Dorsal-fin origin at tip of rostral hook, located ventral to visible part of mouth opening. Anteriormost rays, from first to approximately 15 th ray, with distinct cup-shaped, fleshy membrane approximately to their midpoints and with their distal halves curved, filamentous, and noticeably free from connecting membrane; remainder of rays connected with membrane at approximately three-fourths the length of each ray and without cup-shaped, fleshy membrane at their midpoints. Anal-fin rays connected by membrane nearly at their distal tips. No scales on blind sides of dorsal- and anal-fin rays. Caudal fin rectangular, moderately long (CFL 17.6–32.2% of SL, X = 22.0%) compared with that of congeners; scales covering both sides of caudal fin proximally for one-fourth or less length of fin, and with scales extending distally on rays to about three-fourths of their lengths. Both pectoral fins well developed; ocularside fin with conspicuous, elongate, second ray reaching just slightly posterior to vertical through body midpoint; length of second ray (OSP 15.0–35.0% of SL, X = 28.8%) increasing proportionally with increasing SL ( Fig. 27D ); OSP shorter than greatest body depth in adults, but nearly equal to body depth in small juveniles; remaining rays gradually decreasing in length ventrally. Blind-side pectoral fin much shorter than ocular-side fin (BSP 8.4–14.9% of SL, X = 11.8%), with rays spaced much closer together than those of ocular-side fin, and without elongate rays. Both pelvic fins well developed; unequal in position and size; surrounding anus; not connected to each other. Ocularside pelvic fin on body midline with its origin nearly at anterior tip of isthmus. Base of first blind-side pelvic-fin ray located at point equal to space between fifth and sixth ocular-side rays, sometimes equal with base of sixth ocular-side ray. Ocular-side rays widely separated and with distal tips free from membrane; first and second rays noticeably shorter than others; rays of ocular-side pelvic fin more robust than those of blind-side fin; posteriormost ocular-side pelvic-fin ray with broad, membranous connection to first anal-fin ray. Blind-side pelvic fin much shorter and with rays spaced more closely together than those in ocular-side fin; first blind-side ray notably slender and short, rays 2–4 becoming progressively more robust, fourth ray longer than others; blind-side pelvic fin without membranous connection to anal fin, but fourth ray, from base to approximately middle of ray, with membranous connection to body region near anus.

Ocular and blind sides of head and body with transforming ctenoid scales with strong ctenii in adults and juveniles of both sexes. Blind-side preopercle and subopercle of adult males with strongly ctenoid scales; whereas, adult females with weakly ctenoid or cycloid scales on preopercle, and with ctenoid scales on subopercle.

Anus on blind side, slightly off body midline, bordered medially by blind-side pelvic fin.

Lateral line straight, except for slight elevation anteriorly above pectoral fin; posteriorly, lateral-line pores extending nearly to 4/5ths of length of ocular-side middle caudal-fin ray, and on blind side to proximal one-third of length of middle caudal-fin ray.

Morphometric variation. Detailed examination of variation in morphometric features based on 34 P. kryptostomus, 33.2–145.1 mm SL, revealed allometric growth evident in most features examined ( Figs. 27 A–J). Values for body depth measurements (BD; Fig. 27A ) varied from 41.6% to 50.4% of SL, and showed positive allometric growth throughout the size range of fish examined. Differences in BD from smallest to largest individuals (ca. 13%) reflects continued deepening of the body with increasing size.

Head length (HL; Fig. 27B ) measurements varied between 26.6% and 32.5% of SL and had less variation (ca. 7%) than did BD measurements. Head length showed slight negative allometry over the size range measured. Smallest fish (to ca. 60 mm SL) had HL values between 26.6–32.5% of SL, whereas fish> 120 mm SL usually had HL values of 26–30% of SL. Smaller fish have proportionally larger heads relative to SL than do larger P. kryptostomus . Head width values (HW; Fig. 27C ) were 41.1–49.3% of SL over the size range measured. Although the data showed slight, but continuous, positive allometric growth of HW over SL, the difference between the smallest and largest fish was only 9%, indicating that HW increases relatively slowly compared to increasing fish size.

Length of the elongate ray in the ocular-side pectoral fin (OSP; Fig. 27D ) also shows continuous, positive allometric growth for fish 33.2–145.1 mm SL. For these, OSP values ranged from 14.4% to 35.0% of SL, representing considerable variation (21%) compared with that observed for other features.

Of six other morphometric features of the head measured ( Figs. 27 E–J), all but SNL displayed allometric growth. Dorsal head width (DHW; Fig. 27E ) and interorbital width (IO; Fig. 27H ) both showed positive allometry throughout the size ranges. Width of the head region dorsal to the eyes varied considerably, with 18% difference between the smallest and largest fish. Variation in IO measurements (5.6–11.2% of HL) was considerably less than that for DHW, but the proportionate growth of this feature steadily increased with increasing fish size. Data for eye to upper mouth values (EUM; Fig. 27J ) revealed that this region of the head undergoes continuous, positive allometric growth with increasing fish size (total range 9.3–18.4% of HL), values varied about 9% between the smallest and largest fish. Continued positive increases in DHW, IO, and EUM values proportional to increasing fish size reflect broadening of head width with growth; this broadening is especially evident in the regions dorsal to, and between, the eyes.

Values for snout length (SNL; Fig. 27F ) were 27.8–33.6% of SL and growth of this feature appears to be isometric, with no clear trends apparent in the plotted data. Measurements of lower eye diameter (ED; Fig. 27G ) varied about 10%, with a negative trend in proportionate growth evident between smaller and larger fish. Values for upper jaw length (UJL; Fig. 27I ) ranged about 9% between smaller and larger fish (24.1–33.3% of HL), and were positively allometric throughout the size range examined.

Colour based on freshly thawed specimens (NMNZ P.046433; USNM 427115; NMNZ P.046439). Background colouration of ocular side of head and body light brown to light gray ( Figs. 25 , 26 B–C). Ocular side with numerous, minute, pinkish spots over entire surface. Base of ctenii at posterior border of many scales on ocular side of head and body black. Neuromasts outlined with black pigment. Scales on various areas of ocular side of head and body highlighted with faint patches of brassy-gold and pinkish pigment. Ocular side of body, from about one-third length of longest ocular-side pectoral-fin ray and continuing to caudal peduncle, with irregular arrangement of clusters consisting of 4–5 black scales semi-enclosing an inner, brighter, pinkish-brown area. Most of ocular side of caudal peduncle with three darkly pigmented areas. Ocular side also with three, conspicuous, larger, irregular, dark blotches along lateral line. Two anteriormost blotches with numerous, small pink spots and scattered white pigment; some specimens also with small pink spots associated with posteriormost blotch.Anteriormost dark blotch located on lateral line about equal with point at mid-length of elongate ocular-side pectoral-fin ray, second blotch just posterior to vertical through body midpoint, and posteriormost blotch located just anterior to caudal peduncle. Second blotch, largest of the three, vertically elongate, ranging from 1–3 scales in width along horizontal axis and extending vertically in length 3–4 scales both dorsally and ventrally from lateral line. Lateral-line pores in region of dark blotches also black. Region around and including axil of ocular-side pectoral fin with black pigment much darker than that on body. Anterodorsal region of head with lighter colouration compared with that on ventroposterior region. Anterior ocular-side nostril tubular with three distinct patches of black pigment along its length. Dorsal surface of eyes, cornea and pupillary operculum gray; pupil outlined with small band of reflective silvery pigment. Mouth margined with black pigment. Exposed portion of ocular-side jaws gray with black margin on vertical portion. Roof of mouth black. Ocular-side inner opercular lining black. Gill filaments dusky gray with central rachis black. Blind side of body uniformly white; some scales on head and body with whitish iridescent sheen. Outer surface of operculum whitish to silvery. Blind-side inner opercular lining without conspicuous pigment. Fleshy finger-like filaments on inner anteroventral margin of skinfold on lower jaw white, conspicuously contrasted against darker colour of lower jaw and operculum.

Ocular side of dorsal fin on head with fine black spots on both fin rays and membrane. Spots more densely concentrated on rays than on connecting membrane. Remainder of fin with series of a single darkly pigmented ray alternating with 1–6 lighter pigmented rays. Anteriormost 5–10 rays with small, white flap of tissue on distal tips; some rays, beginning with those posteriorly on head and continuing caudally, with yellowish-orange pigment on entire (most cases) posterior side of rays. Anal fin with same colour pattern as that on dorsal fin, except for fewer darkly pigmented rays. Most posterior anal-fin rays yellowish, posteriormost rays entirely yellow with a cluster of dark melanophores on their tips. Ocular side of caudal fin with small, black spots along entire length of rays; very few spots on connecting membrane. Axil of ocular-side pectoral fin sometimes with small patch of black or blackish-brown pigment, rays with same general colour as that on adjacent body. Two dorsalmost rays with pinkish overtones and three small areas of black pigment along their lengths. Distal tips of rays black. Ocular-side pelvic fin with similar colouration as that on dorsal and anal fins, except first pelvic-fin ray yellowish-pink. Blind sides of dorsal and anal fins uniformly white; caudal fin mostly white, except for fine black spots on membrane. Blind-side pectoral fin white. Blind-side pelvic fin iridescent white, except anterolateral side of first ray pink.

Colour of preserved specimens ( Fig. 26B ; USNM 427115). Ocular-side background colouration uniformly greenish- or yellowish-brown to grey sometimes with up to three, large, irregular, dark blotches on lateral line, and with smaller dark blotches irregularly placed over ocular surface. Axil of ocular-side pectoral fin with small patch of black or blackish-brown pigment. Some anterior sensory pores ringed and clearly outlined with brown pigment. Inner lining of ocular-side opercle and roof of mouth black; inner lining of blind-side opercle without conspicuous pigment. Dorsal and anal fins with pattern of single, darkly streaked ray alternating with 4–6 lightly pigmented rays; this alternating pattern more prominent in anterior half of these fins. Blind side uniformly white or yellowishwhite.

Size and maturity. Peltorhamphus kryptostomus reaches a maximum size of about 145 mm SL ( Table 4). No sexual dimorphism in size was observed for 56 specimens for which size and sex information was obtained ( Table 4). The largest specimen examined is a female 145.1 mm SL, the largest male 135.2 mm SL. Of 56 specimens, 19 are males (52.9–135.2 mm SL) and 37 are females (33.2–145.1 mm SL).

Of the females, 16 (33.2–113.4 mm SL), are immature ( Fig. 13D ). Seven immature females smaller than 80 mm SL show little, if any, elongation of their ovaries; nine females (75.8–113.4 mm SL) have partially elongate ovaries. Mature females (N = 21), i.e., those with elongate ovaries, are 85.7–145.1 mm SL. Females attain sexual maturity beginning at sizes between 85–100 mm SL; three of four females 80–90 mm SL, and three of 10 females 91–100 mm SL, are mature. Seven females in the latter size range, the largest 95.7 mm SL, have ovaries still undergoing posterior elongation and were assessed as immature. Of 16 females Ξ 101 mm SL, 15 are sexually mature, having fully elongate ovaries, including some with visible ova in various stages of development. The exceptional female in this group, of 113.4 mm SL, has only partially elongate ovaries. Based on these limited data, female P. kryptostomus begin to mature sexually at sizes as small as 86 mm SL. By sizes Ξ 101 mm SL, all, with rare exception, have reached sexual maturity.

Etymology. The name “ kryptostomus ” is derived from the Greek “ krypto ” meaning hidden and “ stomus ” meaning mouth, in reference to the mouth on the ocular side being mostly hidden by the broad rostral flap.

Distribution ( Fig. 14D ). Peltorhamphus kryptostomus is endemic to New Zealand waters, with a restricted distribution in nearshore coastal waters and bays along the southeast coast of South Island from off Akaroa (43°50ꞌS) to off the Caitlins at 46°40.55ꞌS, 169°14.50ꞌE.

Habitat and bathymetric distribution. Peltorhamphus kryptostomus is a shallow-water species that occurs in 1.5–40 m ( Table 5). The majority of specimens (70 of 81) examined in this study were caught between 11 m and 20 m; 8 of 81 were collected in 1.5–5.0 m, 2 of 81 were taken at 21 m; only 1 of the 81 was taken at 40 m.

Of 49 fish with size and depth information ( Table 13), it appears that small fish occur in shallower waters than do larger fish. All eight fish smaller than 80 mm SL were collected at the shallowest depths (1.5–5.0 m). Fish larger than 81 mm SL were collected deeper in 11–40 m, the majority in 11– 20 m. The 12 largest fish (121–145 mm SL) were captured between 11–40 m, with only three specimens (101–140 mm SL) collected deeper than 20 m.

Biology. Other than information summarized above, little else is known about the ecology of this species.

Remarks. James (1972) recognized three species, and only for specimens identified as a ‘population’ of P. latus from Blueskin Bay (mostly fish> 115 mm SL) was any significant variation in body proportions apparent. For this ‘population,’ James reported that body depth, snout length, and upper jaw length were relatively greater than comparable morphometric features noted for other populations of P. latus . Differences in eye size between the Blueskin Bay ‘population’ and others were also noted.

My examination of specimens from Blueskin Bay, including some of those previously identified by James as P. latus (including two paratypes), reveals that most, especially many of the larger specimens, are P. kryptostomus . This species occurs sympatrically and sometimes syntopically in Blueskin Bay with P. latus . Since both species were included in James’ samples from Blueskin Bay, morphometric comparisons between this ‘population’ and other populations of P. latus were compromised. The question then is, did the differences James observed in body depth, snout length, upper jaw length, and eye size for his Blueskin Bay ‘population’ of P. latus actually reflect differences between two sympatric congeners?

To address this question, 18 morphometric features of specimens of all sizes identified in this study as P. kryptostomus and P. latus were compared. Data were taken from specimens of each species collected throughout their respective geographic ranges, including P. latus from Blueskin Bay, and all morphometric values expressed as percent of SL or HL. Comparisons of morphometric features (summarized in Table 2 ) revealed large overlaps between these species in most characters examined. The four morphometric characters (BD, SNL, ED, UJL), specifically identified by James (1972) as being significantly different between the Blueskin Bay ‘population’ (= composite sample including two species) versus those of other populations of P. latus , were examined in greater detail to assess their value as diagnostic characters useful for separating the two species.

Among these features, ranges for BD measurements overlapped nearly completely between the two species (BD 42.5–50.4% of SL in P. kryptostomus vs. 39.7–50.1% in P. latus ), with the mean value only slightly greater in P. kryptostomus (X = 46.7% of SL) compared with that in P. latus (X = 44.1%). Likewise, significant overlaps and only slight differences between these species were also observed in SNL (7.8–10.4% of SL, X = 8.8% in P. kryptostomus vs. 6.8–10.2% of SL, X = 8.5% in P. latus ) and ED (3.8–6.6% of SL, X = 5.2% for P. kryptostomus vs. 5.0–7.2% of SL, X = 5.3% for P. latus ). When ED was expressed as a ratio of HL, the smaller eye of P. kryptostomus (ED 13.5–23.3% of HL, X = 18.6% vs. ED 17.7–27.3% of HL, X = 21.9% in P. latus ) became slightly more apparent ( Fig. 24D ). However, the large overlap rendered this feature ineffective as a diagnostic character for distinguishing these species. Measurements of UJL ( Fig. 24D ), although slightly larger in P. kryptostomus compared with those of P. latus (UJL 7.3–9.2% of SL, X = 8.2% vs. 6.0–8.9% of SL, X = 7.1% in P. latus ), also overlapped between species, and was also determined ineffective as a good diagnostic character. Of four morphometric features James (1972) found to differ significantly between the purported Blueskin Bay ‘population’ versus that of other populations of P. latus , none provide sufficient separation to be usefully diagnostic.

The large degree of overlap observed in the present study ( Table 2 ) among many of the other morphometric features of these two species reveals the overall similarity between P. kryptostomus and P. latus in body shapes. Based on their similarities, it is understandable why James, despite recognizing some differences between Blueskin Bay specimens and those from other areas, concluded these differences only represented population variation and not that of co-occurring species.

Despite these similarities, ample support for recognizing P. kryptostomus as a species distinct from P. latus includes two other morphometric features not examined by James (1972): IO width ( Fig. 24B ) and EUM distance ( Fig. 24A ). The eyes of P. kryptostomus are more widely separated (IO space 5.6–11.2% of HL, X = 8.8%) compared with the nearly contiguously positioned eyes of P. latus (IO 3.8–7.9% of HL, X = 5.4%). Peltorhamphus kryptostomus also has a much larger separation between the anteroventral margin of the lower eye and the upper margin of the rostral flap above the mouth (EUM 9.3–18.4% of HL, X = 14.9%) compared with the smaller EUM (6.0–11.7% of HL, X = 9.0%) for P. latus . Other differences, including size and position of gillrakers on the first arch, scale counts in IO and EUM spaces, presence vs. absence of finger-like filaments on the inner anteroventral margin of the lower jaw, presence of ctenoid scales on the blind-side preopercle and posterodorsal region of the blind-side opercle in P. kryptostomus (vs. cycloid scales in both locations in P. latus ) are suitable diagnostic features that distinguish these as distinct species. Further differences between these species are highlighted in the Comparisons section below.

Two lots, NMNZ P.005147 and BMNH 1970.12.15.2, each containing a single specimen from Blueskin Bay, Otago, South Island, are part of the paratype series of P. latus selected by James (1972). These two specimens are herein re-identified as P. kryptostomus , but are not designated as paratypes of P. kryptostomus .

As mentioned above, one character distinguishing P. kryptostomus and P. latus is the presence in P. kryptostomus (vs. absence in P. latus ) of finger-like filaments on the inner skinfold of the anteroventral margin of the lower jaw. Although this feature is prominent in the majority of specimens examined, five of the 63 (8%) specimens of P. kryptostomus examined, lacked these finger-like filaments. This was thought to result from their condition and/or long-term preservation. These fish were collected and preserved in the 1970s, and some were also partially dissected for otolith extraction. Despite lacking obvious filaments, these specimens possessed other characters that distinguish them as P. kryptostomus . Uncompromised data from these specimens, other than that for the finger-like filaments, were included in tallies for P. kryptostomus .

Comparisons. Features that distinguish P. kryptostomus from its congeners were discussed in detail in the Comparisons sections for P. novaezeelandiae , P. tenuis , and P. latus , respectively. In addition to its smaller size and scale type on the blind side (discussed above), P. kryptostomus differs from P. novaezeelandiae by its lower and nearly non-overlapping counts of dorsal- and anal-fin rays, and counts for lateral-line scales (compare frequency distributions for respective meristic features for these species in Table 1). Peltorhamphus kryptostomus also has more gillrakers on the upper limb of the first gill arch (4–6, usually 4–5 vs. 1–6, usually 3–4, in P. novaezeelandiae ). The gillrakers on the first arch of P. kryptostomus are long and pointed, and some overlap the uppermost gillraker(s) on the lower limb of the first arch, whereas in P. novaezeelandiae the gillrakers on the first arch are short, triangularshaped and those on the upper limb are noticeably shorter and rounder and not overlapping those on the lower limb of the arch (compare Figs. 12A and 12D ). Peltorhamphus kryptostomus also differs from P. novaezeelandiae in having fewer supracranial pterygiophores (21–26, usually 23–24 vs. 23–29, usually 25–28). Peltorhamphus kryptostomus can further be distinguished from P. novaezeelandiae in having black pigment on the entire inner lining of the ocular-side opercle and on the entire roof of the mouth, which is lacking in P. novaezeelandiae . It is further distinguished from P. novaezeelandiae by its larger, more conspicuous pupillary operculum, and, in adults, by its narrower interorbital width (usually IO <eye diameter compared with that of larger juveniles and adult P. novaezeelandiae whose IO is greater than the eye diameter).

Peltorhamphus kryptostomus is readily distinguished from P. tenuis by differences in ocular-side colour patterns. Peltorhamphus kryptostomus has uniform colouration without longitudinal lines vs. P. tenuis often with faint series of longitudinal lines. Differences are also in pigmentation of the inner opercular lining and mouth; P. kryptostomus with roof of mouth and ocular-side inner opercular lining black vs. P. tenuis with dusky inner opercular lining and unpigmented roof of mouth. Peltorhamphus kryptostomus also differs from P. tenuis in having fewer total vertebrae (37–38 in P. kryptostomus vs. 40–43); fewer dorsal-fin rays (88–97 vs. 98–116); fewer lateral-line scales (64–82 vs. 82–105); more gillrakers on the lower limb of the first gill arch (10–14, usually 11–13 vs. 5–12, usually 8–11); and in having fewer supracranial pterygiophores (21–26, usually ± 25 vs. 25–31, usually 26–29).

These species also have conspicuous differences in morphometric features, with P. kryptostomus having a much deeper body (BD 42.5–50.4% of SL, X = 46. 7%) compared to the narrower, elongate body (BD 31.2–42.3% of SL, X = 36.3%) of P. tenuis ( Fig. 20C ); P. kryptostomus has a much shorter second ocular-side pectoral-fin ray usually much shorter than the body depth versus a longer (usually Ξ body depth) second ocular-side pectoral-fin ray in P. tenuis ; P. kryptostomus also has a slightly longer head (HL 26.1–32.5% of SL, X = 28.4% vs. HL 20.9–27.9% of SL, X = 24.7%; Fig. 20B ), and a wider caudal peduncle (CPD 9.5–11.9% of SL, X = 10.7% vs. 6.9–10.2% of SL, X = 8.7%). Other differences in morphometric features (HW; SNL; RHL; etc.) between these species appear in the summarized data presented in Table 2 . Qualitative differences between these species include the absence (vs. presence in P. tenuis ) of scales on blind sides of the dorsal- and anal-fin rays (best developed in specimens> 70 mm SL); presence (vs. absence) of a pupillary operculum; and by differences in size, robustness and position of gillrakers on the upper limb of the first gill arch (compare Figs. 12D vs. 12B).

Of species in the genus, P. kryptostomus is most similar to P. latus : both reach similar maximum sizes ( Table 4) and both feature similar lower meristic values compared with those of P. novaezeelandiae and P. tenuis ( Table 1). Both species also have similar body shapes with their greatest body depths being located anterior to the body midpoint and with a more rapid posterior taper beyond this point (compare Figs. 21–22 with Figs. 25–26 ).

Despite similarities in size and body shapes, P. kryptostomus is distinguished from P. latus by differences in meristic and morphometric characters, including several features of the head ( Figs. 28 A–D), and in pigmentation. Features useful for separating the two species include the usual presence of 1–4 finger-like filaments on the inner anteroventral margin of the fleshy skinfold on the ocular-side lower jaw in P. kryptostomus , absent in P. latus ; in usually having 4–5 scales between the anteroventral margin of the lower eye and dorsal margin of the mouth opening vs. 2–3 scales in this space in P. latus (compare Figs. 28A and 28B ); in having the ventralmost gillraker on the upper branch of the first gill arch overlapping the dorsalmost gillraker of the lower branch of this arch vs. ventralmost gillraker on upper branch of first gill arch not overlapping dorsalmost gillraker of lower branch of this arch in P. latus (compare Figs. 12D vs. 12C); in having fewer supracranial pterygiophores (21–26, usually 23–24 vs. 23–29, usually 24–28, in P. latus ); and more (14–20, but usually 15–18) total gillrakers compared with that of P. latus (8–16, usually 10–14). Peltorhamphus kryptostomus also has ctenoid scales on the blind-side preopercle and posterodorsal opercle, whereas P. latus has cycloid scales in both locations.

Morphometric features that distinguish these species include differences in EUM ( Fig. 24A ), ED ( Fig. 24B ), and IO width ( Fig. 24C ), illustrated in Figs. 28 A–28B, and to a lesser degree by differences in UJL ( Fig. 24D ). The EUM distance (9.3–18.4% of HL, X = 14.9%) is larger in P. kryptostomus compared with that (6.0–11.7% of HL, X = 9.0%) of P. latus ( Fig. 24A ); and, P. kryptostomus also has a smaller eye (ED 13.5–23.3% of HL, X = 18.6%; Fig. 24B ) than does P. latus (17.7–27.3% of HL, X = 21.9%). Interorbital width in P. kryptostomus ( Fig. 24C ) is wider (IO 5.6–11.2% of HL, X = 8.8%) compared with that (IO 3.1–7.9% in HL, X = 5.0%) of P. latus . Usually, P. kryptostomus also has a larger UJL compared ( Fig. 24D ) with that of P. latus .

Most specimens of P. kryptostomus lack darkly streaked dorsal- and anal-fin rays altogether (vs. dorsal and anal fins of P. latus with conspicuous series of a single, darkly streaked ray alternating with multiple (4–8) lightly pigmented rays throughout the lengths of the dorsal and anal fins). When specimens of P. kryptostomus have darkly streaked fin rays, they are fewer in number and not as regularly spaced as are those in P. latus .

Key to species of Peltorhamphus

1a Second ocular-side pectoral-fin ray elongate, longer than (in specimens ± 130 mm SL), or equal to (in specimens> 130 mm SL), maximum body depth; no pupillary operculum; specimens larger than about 70 mm SL with small, ctenoid scales on basal halves of blind sides of dorsal- and anal-fin rays ( Fig. 2C ); ocular-side colouration with series of faint longitudinal lines; usually 40–42 total vertebrae................................................................. Peltorhamphus­tenuis

1b Second ocular-side pectoral-fin ray elongate, but usually noticeably shorter than maximum body depth; pupillary operculum present or absent; no scales on blind sides of dorsal- and anal-fin rays; ocular-side colouration without series of faint longitudinal lines; less than 40 total vertebrae......................................................................... 2

2a Inner anteroventral margin of fleshy skinfold on ocular-side lower jaw without finger-like filaments (viewed from blind side, Fig. 3B ); usually only 1–2 scales in diagonal row between anteroventral margin of lower eye and dorsal margin of mouth opening; eyes relatively large, diameter of lower eye greater than interorbital space, and greater than distance between anteroventral margin of lower eye and dorsal margin of rostral flap above mouth; interorbital space narrow, usually less than eye diameter and usually with only 1–2 scales......................................................... Peltorhamphus­latus

2b Inner anteroventral margin of fleshy skinfold on ocular-side lower jaw with 1–5 fleshy, finger-like filaments (viewed from blind side, Fig. 3A ); fish> 40 mm SL with more than 2 (usually 4–5) scales in diagonal row between anteroventral margin of lower eye and dorsal margin of rostral flap above mouth ( Fig. 2A ); eyes relatively small, diameter of lower eye usually less than, or only equal to, interorbital space; diameter of lower eye usually less than distance between ventral margin of lower eye and dorsal margin of mouth opening; interorbital space wide, usually greater than eye diameter, and with 3 or more scales (in fish> 40 mm SL)......................................................................................... 3

3a Entire inner lining of ocular-side opercle and roof of mouth black; gillrakers on first arch of blind side long and robust ( Fig. 12D ), upper limb gillrakers equal in length to those on lower limb; posterior gillrakers on upper limb of first arch on blind side usually overlapping dorsalmost first or second gillrakers on lower limb; fish> ca. 80 mm SL with ctenoid scales on mid-body region of blind side and on blind-side preopercle and subopercle; pupillary operculum relatively large, conspicuous.................................................................................... Peltorhamphus­kryptostomus

3b Inner lining of ocular-side opercle black only on dorsoposterior region (if at all); roof of mouth without black pigmentation; gillrakers on first arch of blind side relatively short, usually much shorter than gillrakers on lower limb, and thin ( Fig. 12A ); posterior gillrakers on upper limb of first arch on blind side not overlapping gillrakers on lower limb ( Fig. 12A ); fish> ca. 80 mm SL with cycloid scales on mid-body region of blind side and also on blind-side preopercle and subopercle; pupillary operculum relatively small, inconspicuous....................................... Peltorhamphus­novaezeelandiae

Figures

FIGURE 2. Selected anatomical features of Peltorhamphus. A. Scales (in black) in diagonal row between anteroventral margin of lower eye (EUM distance) and dorsal margin of rostral flap above mouth. B. Pupillary operculum (indicated by arrow) of P. latus. C. Scales on blind sides of dorsal- and anal-fin rays in P. tenuis. Drawn by: M. Freeborne.

FIGURE 3. Blind-side view of ventral mouth region illustrating anteroventral skin fold on ocular-side lower jaw in Peltorhamphus. A. Lower-jaw marginal skinfold with filaments present (P. novaezeelandiae, P. tenuis, and P. kryptostomus n. sp.). B. Lower-jaw marginal skinfold without filaments (only P. latus). Drawn by: M. Freeborne.

FIGURE 5. Differences in anterior head shapes, relative sizes of eyes and interorbital distances, and rostral hooks of Peltorhamphus. A. P. tenuis (drawn from NMNZ P.005421, 122 mm SL). B. P. latus (drawn from NMNZ P.041941, 129 mm SL). C. P. kryptostomus n. sp. (drawn from NMNZ P.046429, 132.0 mm SL). Drawn by: M. Freeborne.

FIGURE 12. Differences in size and shape of gillrakers on the first gill arch of Peltorhamphus. A. P. novaezeelandiae (drawn from NMNZ P.009457, 196 mm SL). B. P. tenuis (drawn from NMNZ P.005421, 124.9 mm SL). C. P. latus (drawn from NMNZ P.041941, 129.0 mm SL). D. P. kryptostomus n. sp. (drawn from NMNZ P.044384, 108.2 mm SL). Drawn by: M. Freeborne.

FIGURE 13. Size (mm SL) and maturity stage for females of Peltorhamphus. A. P. novaezeelandiae. B. P. tenuis. C. P. latus. D. P. kryptostomus n. sp. Number at top of each column corresponds to number of females within each size range.

FIGURE 14. Geographic distributions of Peltorhamphus. A. P. novaezeelandiae. B. P. tenuis. C. P. latus. D. P. kryptostomus n. sp. Black circles in B, C, and D represent collection sites for the holotypes of P. tenuis, P. latus and P. kryptostomus n. sp., respectively. Prepared by: J. Barker.

FIGURE 20. Selected morphometric features of Peltorhamphus tenuis compared with those of P. latus, and P. kryptostomus n. sp. A. Head length (HL) as percent of SL vs. SL (in mm) for P. tenuis and P. latus. B. Head length (HL) as percent of SL vs. SL (in mm) for P. tenuis and P. kryptostomus n. sp. C. Body depth (BD) as percent of SL vs. SL (in mm) for P. tenuis, P. latus, and P. kryptostomus n. sp.

FIGURE 21. Peltorhamphus latus holotype (NMNZ P.005139), preserved, Wellington Harbour, North Island, New Zealand. Photo: C. Struthers.

FIGURE 22. Peltorhamphus latus. A. NMNZ P.048368, 36.2 mm SL, Hokianga Harbour; fresh specimen. B. NMNZ P.046428, 119.4 mm SL, off Southland, South Island; freshly frozen, thawed. Photos: C. Struthers.

FIGURE 24. Comparisons of selected morphometric features of Peltorhamphus latus and P. kryptostomus n. sp. as percent of HL versus HL (in mm). A. Eye to upper mouth distance (EUM). B. Eye diameter (ED). C. Interorbital width (IO). D. Upper jaw length (UJL).

FIGURE 25. Peltorhamphus kryptostomus n. sp., holotype (NMNZ P.046433, 75.8 mm SL), freshly frozen, thawed; Aramoana Flats, Otago Harbour, South Island, New Zealand. Photo: C. Struthers.

FIGURE 26. Peltorhamphus kryptostomus n. sp. paratypes. A. NMNZ P.005412, 105.6 mm SL, Akaroa, Canterbury, South Island; preserved. B. USNM 427115 (formerly NMNZ P.046437), 56.1 mm SL, Otago Harbour, South Island; freshly frozen, thawed. C. NMNZ P.046439, 33.2 mm SL, Otago Harbour, South Island; freshly frozen, thawed. Photos: C. Struthers.

FIGURE 27. Selected morphometric features for 34 specimens of Peltorhamphus kryptostomus n. sp. 33.2–145.1 mm SL. A-D. Body depth (BD), Head length (HL), Head width (HW), and Ocular-side pectoral fin (OSP) expressed as percent of SL versus SL (in mm), respectively. E–J. Dorsal head width (DHW), Snout length (SNL), Eye diameter (ED), Interorbital width (IO), Upper jaw length (UJL), and Eye to upper mouth distance (EUM) expressed as percent of HL versus HL (in mm), respectively.

FIGURE 28. Differences between Peltorhamphus latus (A) and P. kryptostomus (B) in the ocular side of the head, including anterior head profiles, relative eye sizes, interorbital distances, and number of scales and distances along the diagonal between the anteroventral border of lower eye and upper margin of the mouth (EUM distance). Drawn by: M. Freeborne.