Dipturus chilensis (Guichenot 1848)

Concha, Francisco J., Caira, Janine N., Ebert, David A. & Pompert, Joost H. W., 2019, Redescription and taxonomic status of Dipturus chilensis (Guichenot, 1848), and description of Dipturus lamillai sp. nov. (Rajiformes: Rajidae), a new species of long-snout skate from the Falkland Islands, Zootaxa 4590 (5), pp. 501-524 : 507-511

Dipturus chilensis (Guichenot 1848)

Yellow-nose skate, raya volantín

Type locality: Quintero, Valparaíso, Central Chile.

( Figures 2–6 ; 12 A–B; Table 2 )

Neotype. Mature male MNHNCL ICT 7549 , tissue voucher No. CHL-88, 90.7 cm TL, collected with a gillnet in Valparaíso Bay, central Chile, southeastern Pacific Ocean (32°53'22.94"S, 71°31'32.16"W; approx. 40 m) on January 8 th, 2014 by Veronica Bueno and Francisco Concha.

Voucher specimens. A total of 49 specimens was collected and observed. Two specimens were kept in the ichthyological collection of the Chilean Museum of Natural History (MNHNCL ICT) in Santiago, Chile: a mature male (MNHNCL ICT 7569; CHL-138), 94.9 cm TL, collected with a bottom longline near Puerto Gala, Aysén, inner waters of Chilean Patagonia, southeastern Pacific Ocean (44°15'30.89"S, 73°12'39.97"W; approximately 400 m), on October 24 th, 2016 by Erwin Pacheco; a mature female MNHNCL ICT 7550, tissue voucher No. CHL-89, 73.5 cm TL, collected with a gillnet off Valparaíso, central Chile, southeastern Pacific Ocean (32°53'22.94"S, 71°31'32.16"W; approx. 40 m), on January 8 th, 2014 by Veronica Bueno and Francisco Concha.

Specimens sequenced. Sequence data for NADH2 were generated for the neotype and 10 additional specimens of D. chilensis . Information on sex, type status, collection number (GCD), and accession numbers for museum and GenBank for each of the specimens is provided in Table 1 .

Diagnosis. A medium-sized species of Dipturus , up to at least 118.0 cm TL (CHL-85). It is distinguishable from its congeners by the following combination of characters: When fresh, dorsal surface of body plain brownish to greyish, with some lighter small spots randomly distributed dorsally; one red to purple ocellus over center of each pectoral fin. When fresh, ocelli with well-defined margins, irregular in shape, usually indistinguishable in fixed specimens; ventrally, white to grey with lighter patches over area of gill openings and beneath mouth; area flanking rostral cartilage membranous and slightly translucent when fresh, opaque and yellowish when fixed; disc relatively broad with angular apices, width 76.4 (75.0; 77.0) % TL; snout relatively short and broad. Tail longer in males (42.2 [40.8] % TL) than in female voucher ([38.8] % TL). Ventral head length 35.1 (34.2; 37.7) % TL; preorbital snout length 2.4 (2.9; 2.9) times distance between orbits; orbit diameter 0.5 (0.5; 0.6) of inter-orbital width. Dorsal surface of disc and tail in males with central longitudinal band of dermal denticles extending from anterior margin of rostral cartilage to tail, including anterior margins of dorsal and caudal fins; thin band of dermal denticles at anterior margins of pectoral fins, extending from anterior fontanelle to front line of alar thorn patches. Dorsal surface of disc and tail of females covered with small dermal denticles, except for external margins of pectoral fins, pelvic fins, and area surrounding caudo-central thorns. Orbital thorns present; single nuchal thorn often absent; both sexes lacking scapular thorns; patch of malar thorns only in adult males; alar thorns only in adult males; medial-dorsal and lateral-dorsal thorns may be present in large specimens, especially in large females (e.g., CHL- 90). Small central-caudal thorns mostly arranged in longitudinal pairs in males and females, additional two longitudinal rows of fine, sharp and posteriorly oriented lateral-caudal thorns may be present in large specimens. Ventral sensory pores small, distinct, black-edged, most abundant on snout and around mouth, scattered over area between gill openings, sparsely spaced on abdominal area and pectoral fins.

Redescription. Morphometric and meristic data are provided for the neotype (mature male, CHL-88) and two vouchers (one mature male and one mature female, CHL-138 and CHL-89, respectively), and are expressed as CHL-88 (CHL-138; CHL-89). Redescription came from fixed and fresh specimens of both sexes unless otherwise indicated. Much of dorsal surface plain light brown to dark grey; some specimens with small, scattered light brownish spots dispersed over dorsal surface of disc ( Fig. 2 A–B); light yellowish-brown coloration or slightly translucent adjacent to rostral cartilage and anterior fontanelle, contrasting with darker area on rostral cartilage ( Fig. 3 A–B). Single irregularly shaped red to purple ocellus with solid margins over center of pectoral fins, conspicuous in fresh specimens, lighter to undetectable in fixed specimens. Anterior margin of pelvic fins whitish. Outer posterior margin of spiracle, base of spiracular pseudo-branch, and area inside spiracle, white ( Fig. 3 A–B).

Ventral surface light grey or whitish to dark brown in center of disc extending to inner half of pectoral fins; darker areas on ventral side of disc mostly restricted to oro-nasal area, inter-branchial space and abdomen, light brown to whitish outer margins, except for posterior margins of pectoral fins, which are brownish ( Fig. 2 C–D); white irregular patches, more conspicuous in fixed specimens, posterior to mouth, gill openings, base of tail, and ventral surface of claspers.

Disc rhomboidal, 1.3 (1.2; 1.2) times broad as long; snout angle in front of spiracles 79.2 (71.7; 75.2) degrees; axis of greatest width at 64.1 (58.3; 63.9) % of TL; anterior margin of disc concave anteriorly, convex anteriorlaterally to eyes, strongly or moderately concave behind line of spiracles in males and females; apex narrowly rounded to sub-angular; posterior margin convex; free rear tip very broadly rounded.

Head elongated, snout narrowly pointed, rigid, pre-orbital snout length 5.0 (6.1; 5.0) times orbit length, 2.4 (2.9; 2.9) times distance between orbits; pre-upper jaw length 1.4 (1.7; 1.9) times distance between nostrils. Orbit small, diameter 0.5 (0.5; 0.6) times distance between orbits. Spiracles 0.8 (0.8; 0.8) times orbit diameter; spiracle opening oval. Nostrils semi-circular, with nearly straight inner margins; anterior nasal flap expanded, not overlapping nostril; anterior margin of nostril flap weakly lobed, partly concealed beneath nasal curtain, posterior inner margin not or barely concealed beneath nasal curtain. Posterior lobes of nostrils forming well developed nasal curtain, produced slightly postero-laterally, slightly concave external margins, with fringed posterior margins, shorter in males than in females, reaching first series of teeth in male neotype, covering whole upper mandible in female voucher ( Fig. 3 C–D). Distance between nostrils 2.1 (2.0; 2.1) distance between first gill slits, 1.2 (1.8; 1.2) distance between fifth gill slits. Upper jaw more arched in males than in female, indented at symphysis; lower jaw convex in both sexes. Teeth uni-cuspid, with sub-circular bases, arranged in longitudinal rows; cusps of medial teeth long, sub-conical, pointed, posteriorly and lingually directed in upper and lower jaws; cusps of lateral teeth shorter and slightly oblique; cusps of all teeth in mature males narrower and longer than in females ( Fig. 3 C–D).

Pelvic fins of medium size, deeply forked ( Fig. 4 A–B); anterior lobe relatively short, slender, bluntly pointed distally, 0.6 (0.6; 0.8) times length of posterior lobe, lateral margin entire, inner margin incised; posterior margin of distal pelvic lobe moderately elongate in males, rounded in females, longer in mature males than in females, 20.3 (18.5; 16.9) % of TL. Claspers elongate, 30.7 (31.0) % of TL, moderately broadened at shield, dorsoventrally depressed at distal lobe, lacking dermal denticles; apopyle and hypopyle distinguishable as narrow slits in external lateral view. Internal components: cleft, shield, slit, spike, spur, and rhipidion; dermal denticles absent ( Fig. 4D ).

Tail relatively short, length from rear of cloaca to tail tip 0.7 (0.7; 0.6) times distance from tip of snout to rear of cloaca. Tail narrowing posteriorly, width at pelvic fin axils 1.1 (1.2; 1.4) times width at mid-length, 1.4 (1.6; 1.4) times width at first dorsal fin origin, 1.2 (1.4; 1.4) times height at pelvic fin axils, 2.0 (1.6; 1.9) times height at midlength, 1.5 (1.4; 1.6) times height at first dorsal fin origin. Tail in males flattened dorsally, convex ventrally at base, becoming depressed and oval medially, triangular between dorsal fins, ventral face almost flat; in females, more uniformly depressed along its length, moderately flattened dorsally, convex ventrally at the base, oval at midlength, triangular with a more flattened base between dorsal fins. Lateral tail fold narrow, relatively long, originating as a low membranous ridge beside or slightly posterior to pelvic axil, extending sub-terminally to tail tip, not obviously broader at any point along its length, maximum width about half caudal fin height in neotype, about as wide as caudal fin height in female voucher.

Dorsal fins sub-equal in size, similar in shape, apices broadly rounded, not fringed ( Fig. 5 A–B), posterior margins shorter than anterior margins, free rear tip broadly rounded. First dorsal fin long and weakly convex, slightly taller and more upright than second; first dorsal fin height 1.7 (1.3; 1.8) in base length. Second dorsal-fin base shorter in males, subequal or only marginally shorter than first dorsal fin base in female voucher; inter-dorsal space moderate ( Fig. 5 A–B), rear tip of first dorsal fin not overlapping base of second; distance from first dorsal fin origin to tail tip 2.7 (2.9; 2.7) times first dorsal fin base length, 3.6 (3.8; 3.9) times caudal fin length; first dorsal fin base length 1.3 (1.3; 1.4) times caudal fin length. Epichordal caudal fin lobe developed; base long, maximum height 0.1 (0.2; 0.1) times base length, relatively uniform in height along its length, dorsal margin weakly convex, connected sub-basally to second dorsal fin; hypochordal caudal lobe absent.

Orbital thorns variable in size and number, with rounded or oval base; in males 6 thorns on each orbit, 2 on preorbit, 3 on mid-orbit, and 1 on post-orbit; in female voucher specimen 4 on pre-orbit, 2 on mid-orbit, 2 on postorbit; anterior and posterior orbital thorns flanked by dermal denticle patches ( Figs. 3 A–B; 12A–B). Distribution pattern and presence of other thorns on disc and tail differ considerably between sexes and may vary within sexes. Malar and alar thorns present only in males; malar thorns ( Fig. 5C ) 18 (6), posteriorly directed, very sharp, not embedded; alar thorns ( Fig. 5D ) 23 (25), medially posterior-directed, some embedded, longer than malar and caudal thorns, with very sharp tips. Single nucal thorn and scattered rostral thorns present or absent in both sexes; scapular thorns absent in both sexes. Single row of approximately 10 medial-dorsal thorns in females of large sizes (e.g., CHL-90), scattered and continuous with central row of caudal thorns. Lateral-dorsal row of about 12 acutely pointed thorns in large females, may extend posteriorly to become one of lateral row of caudal thorns. Males with 3 rows of caudal thorns; central row of thorns 30 (23) ( Fig. 4 A–B), posteriorly directed, extending in linear series, mostly in pairs, beginning posteriorly to pelvic girdle and extending to first dorsal fin; about 6 widely spaced lateral-caudal thorns on each side of central row from behind the pelvic axil. Female voucher specimen (CHL-89) with 3 rows of caudal thorns; central row of 31 thorns to first dorsal fin; lateral rows of 7 posteriorly directed thorns. Additional rows of lateral-caudal thorns may be present in large specimens, merging posteriorly to pelvic fin axils, above lateral tail fold and beneath upper lateral caudal row, and extend to second dorsal fin (e.g. CHL- 90); inter-dorsal thorns 3 (2; 3), not aligned, posteriorly directed, sharp.

Distribution pattern and abundance of dermal denticles on dorsal surface of disc and tail sexually dimorphic ( Fig. 12 A–B). In males, denticles small and sparse, except in anterior portion of rostrum, where large and small denticles occur; dense, narrow denticle band along antero-lateral margin of disc, beginning well anteriorly to malar thorns, reaching to about half of anterior margin of pectoral fin; denticle band covering tip of snout, rostral cartilages, inter-orbital and inter-spiracular spaces, and area behind spiracles; longitudinal patch of denticles along mid-dorsal surface extending to tail tip; on tail mostly flanking central-caudal thorns; fine band of dermal denticles on anterior margin of dorsal fins, sparse over caudal fin; ventral snout and oro-nasal area with scattered, small denticles; dense denticles band beneath rostral cartilage, disc margin to level of about first gill slits, small longitudinal band of flattened and scattered denticles along tail from about posterior margin of pelvic fins. In females, dermal denticles covering most of dorsal surface of disc, pelvic fins, and dorsal and caudal fins on tail; denticles absent only on anterior fontanelle, orbits, spiracles, external margins of disc, and area surrounding caudal-central thorns ( Fig. 12 A–B). Ventrally, fine dermal denticle bands on anterior margins of disc and scattered over snout; tip of snout more densely covered; small and randomly distributed denticles around cloaca and along tail, not forming defined patches or bands.

Tooth rows ( Fig. 3 C–D) in upper jaw 42 (45; 36); tooth rows in lower jaw 42 (45; 33). In neotype, pectoral-fin propterygial radials 31, mesopterygial radials 15, metapterygial radials 33, total radials 79; pelvic-fin radials 20; trunk vertebrae 25, pre-dorsal caudal vertebrae 60, vertebrae between origins of dorsal fins 20, total vertebrae about 143.

Egg capsule ( Fig. 6 ) moderate in size, ranging from 9.4 to 14.4 cm in length excluding horns, 6.4 to 7.6 cm in width, barrel shaped, golden brown when fresh, blackish after fixation. Surface smooth with fine longitudinal striations, dorsal surface convex. Anterior horns short, inwardly ventrally curved, not overcrossing; posterior horns moderately long, narrowing posteriorly, not tendril-like. No additional adhesion fibers present. Anterior margin concave, lateral keels present, posterior apron straight, not fringed when recently laid, becoming fringed with time. A more detailed description and observations on oviposition rate can be seen in Concha et al. (2012).

Size. Size at hatching and incubation period 17.2 cm TL and 252 days, respectively ( Concha et al. 2018). Minimum and maximum reported TL 16 and 152 cm, respectively, reported by Fuentealba & Leible (1990) and Licandeo & Cerna (2007), respectively.

Distribution. Known from coastal waters from central Chile to the Strait of Magellan.

Comparisons. The only reported sympatric congener of D. chilensis in the southeastern Pacific is the Roughskin skate, Dipturus trachydermus . Adults of the former attain a much smaller size than those of the latter (152 cm versus 257.7 cm, respectively) ( Licandeo et al. 2006; 2007). The disc of D. chilensis is relatively narrower than that of D. trachydermus (approx. 72.7% versus 76.0% of TL, respectively) and also darker in coloration (see Krefft & Stehmann 1975). Dorsally, D. chilensis is covered with defined patches of small dermal denticles, whereas the dermal denticles of D. trachydermus are wider and distributed irregularly throughout the dorsal and ventral surfaces of the body. The dermal denticles on the dorsal surface of the snout of D. chilensis are restricted to the surface of rostral cartilage, while the dermal denticles of D. trachydermus also cover the membranous areas flanking the rostral cartilage. The presence of scattered, thick, small dermal denticles throughout the surface of the claspers of D. trachydermus , even in sub-adults, contrasts sharply with the smooth claspers of D. chilensis . Additionally, the distal lobe of the clasper of D. trachydermus is pointed, whereas it is flattened in D. chilensis . Six additional species of Dipturus have been reported off the coasts of the southwestern Atlantic: D. argentinensis (see Díaz de Astarloa et al. 2008), D. bullisi (see Bigelow & Schroeder 1962), D. leptocaudus (see Krefft & Stehmann 1975), D. mennii (see Gomes & Paragó 2001), D. teevani (see Bigelow & Schroeder 1951), and a taxon previously referred to as D. chilensis or D. flavirostris , described as D. lamillai sp. nov. here. Dipturus chilensis differs from the first five species in different combinations of characters. The disc of D. chilensis is relatively wider than those of D. argentinensis , D. leptocaudus , and D. teevani (i.e., approx. 76.0 versus 74.8, 68.5 and 72.7 % of TL) ( Díaz de Astarloa et al. 2008; Krefft & Stehmann 1975; Bigelow & Schroeder 1951). The disc of D. chilensis is narrower than that of D. bullisi (76.0% versus 80.0% of TL) ( Bigelow & Schroeder 1962). Whereas the tail of D. chilensis narrows posteriorly, in D. teevani the tail widens posteriorly ( Bigelow & Schroeder 1951). Furthermore, whereas the lateral tail folds are subterminal in D. chilensis , they reach only half the length of the caudal fin in D. teevani . Additionally, whereas the tail of D. chilensis is about 40% of TL, those of D. argentinensis , D. bullisi , and D. leptocaudus are longer (i.e., 47.2, 45.7, and 48 % of TL, respectively) ( Díaz de Astarloa et al. 2008; Bigelow & Schroeder 1962; Krefft & Stehmann 1975). While the dorsal fins of D. chilensis are not connected to one another and thorns are present in the inter-dorsal space, the dorsal fins of D. teevani are connected at their bases by a membranous bridge. Scapular thorns are absent in D. chilensis but present in D. mennii and D. leptocaudus (see Gomes & Paragó 2001; Krefft & Stehmann 1975). Dipturus chilensis has more than four inter-orbital thorns on each orbit and also has three rows of caudal spines on the tail, whereas D. bullisi has only two inter-orbital spines on each orbit and a single row of caudal thorns ( Bigelow & Schroeder 1962). Finally, well defined patches of dermal denticles are found throughout much of the dorsal surface of the body of D. chilensis , but in D. argentinensis , D. leptocaudus , and D. teevani , dermal denticles are mostly restricted to the dorsal area of the snout ( Díaz de Astarloa et al. 2008; Krefft & Stehmann 1975; Bigelow & Schroeder 1951).

Figures

FIGURE 2. Adult specimens of Dipturus chilensis: (A, C) Dorsal and ventral views of male (CHL-98), respectively. (B, D) Dorsal and ventral view of female voucher (MNHNCL ICT 7550; CHL-89), respectively. Scale-ruler: 15 cm.

FIGURE 3. Adult specimens of Dipturus chilensis: (A, C) Dorsal view of head and oro-nasal area, respectively, of male neotype (MNHNCL ICT 7549; CHL-88). (B, D) Dorsal view of head and oro-nasal area, respectively, of female voucher (MNHNCL ICT 7550; CHL-89).

FIGURE 4. Adult specimens of Dipturus chilensis: (A) Dorsal view of tail of male neotype (MNHNCL ICT 7549; CHL-88). (B) Dorsal view of tail of female voucher (MNHNCL ICT 7550; CHL-89). (C) Ventral view of of male neotype (MNHNCL ICT 7549; CHL-88). (D) Internal components of right clasper, lateral view. cf—cleft, dl—distal lobe, hp—hypopyle, rh—rhipidion, sh—shield, sl—slit, sk—spike, and sp—spur.

FIGURE 5. Adult specimens of Dipturus chilensis: (A) Dorsal and caudal fins adult male (CHL-98). (B) Dorsal and caudal fins of female voucher (MNHNCL ICT 7550; CHL-89). (C) Left malar thorns of male neotype (MNHNCL ICT 7549; CHL- 88). (D) Left alar thorns of adult male voucher (MNHNCL ICT 7569; CHL-138).

FIGURE 6. Dorsal view of a fresh egg capsule of Dipturus chilensis extracted from oviduct of adult female captured in Valparaíso, Chile, close to type locality.

FIGURE 12. Line drawings depicting areas covered by dermal denticles in dorsal view of adults of (A, B) male and female of Dipturus chilensis, respectively, and (C, D) male and female of Dipturus lamillai sp. nov., respectively.