Carcharhinus obsolerus White, Kyne & Harris, 2019

White, William T., Kyne, Peter M. & Harris, Mark, 2019, Lost before found: A new species of whaler shark Carcharhinus obsolerus from the Western Central Pacific known only from historic records, PLoS ONE (e 0209387) 14 (1), pp. 1-24 : 7-16

publication ID	https://doi.org/ 10.1371/journal.pone.0209387
DOI	https://doi.org/10.5281/zenodo.13325987
persistent identifier	https://treatment.plazi.org/id/03A3435F-FFE9-132B-FDCA-FA5FFAC1FAD5
treatment provided by	Felipe
scientific name	Carcharhinus obsolerus White, Kyne & Harris
status	sp. nov.

Treatment

Carcharhinus obsolerus White, Kyne & Harris sp. nov.

urn:lsid:zoobank.org:act:DCE2AA0F-1C75-4849-B572-4FD5472D57D1 .

Synonymy. Carcharhinus sp. : [ 15]: 517, 520, 523, 536 (Borneo); [ 16]: 319, 321, 327 ( Vietnam, Borneo, and Thailand); [ 32]: 1359, fig ( Vietnam, Borneo, and Thailand)

Carcharhinus porosus : [ 19]: 71 (Borneo, Saigon, and Bangkok)

Carcharhinus undescribed small species: [ 33]: 497 (Borneo, Vietnam, and Thailand)

Carcharhinus sp. (= ‘ Carcharhinus porosus ’): [ 32]: 1322.

Carcharhinus sp. A : [ 17]: 307, fig, pl. 62 (Borneo, Vietnam, and Thailand); [ 18]: 103, fig 50

Holotype. NMW 61463 View Materials , female 433 mm TL, Bangkok, Thailand, no date or collector recorded.

Paratypes. ANSP 76859 About ANSP , female late-term embryo 339 mm TL, Ho Chi Minh City, Vietnam, Dec. 1934, coll. H. Rutherfurd ; ANSP 77121 About ANSP (paratype of Carcharhinus tephrodes

Fowler), female 370 mm TL, Baram, Sarawak, Malaysian Borneo, 1897, coll. A.C. Harrison Jr. & H.M. Hiller.

Diagnosis. A small species of Carcharhinus with: a slender body and tail; no interdorsal ridge; head parabolic in dorsal view, relatively wide, interorbital space 11.2–12.0% TL; eyes relatively large, length 2.4–2.9% TL, 10.0–15.1 times in head length; no row of enlarged hyomandibular pores alongside each mouth corner; upper anterior teeth broadly triangular and serrated, with large and coarse (non-lobate) serrations basally; lower anterior teeth with narrower, mostly straight cusps; cusps of upper and lower anterolateral teeth with apical margin slightly recurved; no lateral cusplets; total tooth row counts 27–31/26–29; posterior edge of the mandibular plate with an elongate and crescentic indentation; second dorsal-fin origin well posterior of anal-fin origin, about opposite anal-fin midbase, second dorsal-fin origin to anal-fin origin 1.3–2.5% TL, 0.3–0.6 times second dorsal-fin base; first dorsal fin triangular, not falcate, origin about opposite first third of pectoral-fin inner margin length, free rear tip just anterior to pelvic-fin origins, length 1.7–1.9 times height, inner margin 1.9–2.5 in base; second dorsal fin much smaller than first, slightly smaller than anal fin; base 1.4–2.0 times height; height 22–31% of first dorsal-fin height; anal fin height 1.2–1.5 times second dorsal height, base 1.1–1.2 times second dorsal-fin base; total vertebral counts 114–120, monospondylous precaudal counts 36–40, diplospondylous precaudal counts 18–19, diplospondylous caudal counts 56–66, precaudal counts 54–58; no distinct black markings on fins.

Description. Body moderately slender ( Fig 1 View Fig 1 ), trunk subcircular and almost pear-shaped in section at first dorsal-fin base, length of trunk from fifth gill slits to vent 1.07 in holotype (1.06–1.09 in paratypes) times head length. Predorsal, interdorsal and postdorsal ridges absent from midline of back, lateral ridges absent from body. Caudal peduncle relatively slender, rounded-hexagonal in section at second dorsal-fin insertion, postdorsal and postventral spaces flattened, lateral surfaces subangular; height of caudal peduncle at 2 nd dorsal-fin insertion 1.07 (1.16–1.40) times its width, 2.08 (1.43–1.48) times in dorsal–caudal space. Precaudal pits present; upper pit a deep, arcuate and crescentic depression; lower pit a much shallower crescentic depression.

Head length to 5 th gill opening 0.76 (0.77) times in pectoral–pelvic space. Head narrow and slightly flattened, ellipsoidal-lenticular in shape in cross-section at eyes. Outline of head in lateral view undulated dorsally, nearly straight on snout, moderately convex above gills ( Fig 2A View Fig 2 ); weakly convex ventrally along lower jaws and beneath gills. In dorsoventral view, head parabolic ( Fig 2B View Fig 2 ); gill septa expanded slightly outwards. No distinctly enlarged hyomandibular pores adjacent to mouth corners. Snout moderately short, preoral snout length 1.07 (0.90– 1.04) times mouth width; tip rounded in dorsoventral view and very weakly indented anterior to nostrils; snout bluntly pointed in lateral view, nearly straight above to weakly convex above and convex below. A narrow, longitudinal band of enlarged pores posterior to eye, almost entirely situated in the whitish ventral colouration (i.e. below the waterline).

External eye opening of fleshy orbit without anterior or posterior notches, circular in shape, with height 0.97 (1.06–1.08) in eye length. Eyes large, length 10.11 (8.11–10.01) in head length; situated laterally, with lower edges not crossing horizontal head rim in dorsal view; subocular ridges absent. Nictitating lower eyelids internal, with deep subocular pouches and secondary lower eyelids fused to upper eyelids. Spiracles absent. Fifth gill slit shortest, third and fourth gill slits largest, fifth about 0.75 (0.81–0.83) of height of third; height of third about 7.58 (8.31– 11.01) in head length and 1.33 (0.91–0.98) times eye length. Gill slits upright, not oblique; margins of gill slits weakly concave. Gill filaments not visible from outside. Upper end of highest gill opening (third) just below level of upper margin of eye. Gill-raker papillae absent from gill arches. Nostrils strongly oblique, slit-like with large oval incurrent apertures; prominent triangular anterior nasal flaps with narrowly pointed tips, mesonarial flaps absent, small suboval excurrent apertures, posterior nasal flaps absent; well in front of mouth; width 2.44 (3.43–3.56) in internarial width, 1.01 (1.29–1.69) in eye length, 1.31 (1.23–1.33) in longest gill-opening.

Mouth moderately rounded and large; width 2.98 (2.70–2.84) in head length; mouth length 1.67 (1.65–1.80) in mouth width. Lips concealing teeth when mouth is closed. Tongue large, flat and broadly rounded, filling floor of mouth. Maxillary valve narrow, width much less than eye diameter, strongly papillose. No large buccal papillae on floor or roof of mouth behind maxillary valve. Palate, floor of mouth and gill arches covered with buccopharyngeal denticles. Labial furrows short, restricted to mouth corners, uppers 0.3 (0.5–0.6)% TL, lowers concealed by overlapping upper lip; anterior ends of uppers far behind eyes by distance of almost half of mouth width.

Dental meristics in the three known specimens range within 13–15 + 1 + 13–15 / 13–14

+ 0–1 + 13–14, with the holotype having 14 + 1 + 14 / 14 + 1 + 14. Pronounced dignathic heterodonty between upper and lower jaws. Upper teeth broadly compressed and blade-like with semi-oblique to distally notched, oblique crowns and even labial surfaces. Lower teeth with narrow, erect, triangular crowns anteriorly, becoming oblique with slightly convex labial surfaces laterally. Post-mandibular indentation of Meckel’s cartilage elongated and shallow ( Fig 3 View Fig 3 ).

Upper jaw gradient monognathic heterodonty present in all tooth groups; one small, well-developed symphysial tooth present. Anterior teeth ( Figs 4A, 4B View Fig 4 and 5A View Fig 5 ) narrow with somewhat linear lower distal crown margins and weekly notched basal margins; mesial crown edges somewhat linear, not convex with apical portion of crowns slightly reflexed; serrations coarser basally and weaker apically. Anterolateral files with considerably more oblique crowns; distal margins notched with strong basal/apical bifurcation of crown; basal margins more coarsely serrated, no enlarged distal serrae present and serrations gradient from outer basal margins to crown notches; lower portion of crowns noticeably serrated, decreasing but present apically; mesial margins linear, not convex with apical portion of crowns slightly recurved mesially; serrations slightly coarser basally, decreasing but present apically. Lateroposterior files with considerably more oblique crowns than laterals; distal margins deeply notched; serrations coarser basally; mesial margins slightly more posteriorly arcuate and lacking mesial recurvature apically.

Lower jaw gradient monognathic heterodonty present but weak in all tooth groups; one small, well-developed symphysial tooth present. Anterior teeth ( Figs 4C, 4D View Fig 4 and 5B View Fig 5 ) with narrow, erect, triangular cusps, moderate in height and not noticeably elongated with strongly

https://doi.org/10.1371/journal.pone.0209387.g003

acuminate apical portions; distal edge of crowns slightly angular and weakly notched; mesial edges of crowns somewhat concave with apical portion slightly recurved mesially; contour of roots not crescentic or arched with evident root lobes; distal and mesial cusp edges moderately serrated; coarser basally. Lateral files more noticeably notched with slightly more angular distal margins; crown feet coarsely serrated on both distal and mesial margins; slightly heavier distally; lower crown portion with slightly acuminate apical margins and moderately serrated edges, decreasing but present apically. Lateroposterior files increasingly angular with heavier distal notches; distal basal margins heavily serrated, less so on mesial margins; lower crown portions moderately serrated, decreasing but present apically; lower cusp portion slightly crescentic with apical portions recurved mesially.

Rostral cartilages moderately slender, not hypercalcified, rostral fenestrae relatively large, rostral tip truncate, not pointed; nasal capsules broad, anterior margins nearly straight; anterior fontanelle moderately expanded, posterior border with a distinct indentation centrally; preorbital processes large, somewhat triangular at tip, relatively narrow based; postorbital processes long and slender; orbits large ( Fig 6 View Fig 6 ).

Lateral trunk denticles small, slightly imbricate, broad, tricuspid ( Fig 7 View Fig 7 ); crowns usually slightly wider than long (sparser smaller denticles slightly longer than wide), with 3 prominent longitudinal ridges (medial ridge slightly stronger and more pronounced) that extend entire length of crown onto cusps; medial cusp short but strong, much shorter than rest of crown, flanked by a pair of slightly shorter lateral cusps.

Pectoral fins short and relatively broad, weakly falcate; anterior margin moderately convex, apices narrowly rounded; posterior margin very weakly concave; free rear tip moderately rounded to somewhat angular, inner margin weakly convex; base broad about 57 (55–59)% of fin length; length from origin to rear tip 1.26 (1.20–1.24) times anterior margin length; larger in area to first dorsal fin; origin under fourth gill slit; fin apex posterior to free rear tip when fin is elevated and adpressed to body.

Pelvic fins small, triangular and not falcate; length of anterior margin 0.50 (0.41–0.42) of pectoral-fin anterior margin; area about 1.5 times that of anal fin; anterior margin nearly straight; apex rounded angular; posterior margin nearly straight; free rear tip bluntly rounded, inner margin nearly straight.

First dorsal fin relatively small, moderately long-based, broad and triangular, not falcate; anterior margin weakly convex; apex moderately rounded; posterior margin distally straight and basally moderately concave; free rear tip acutely pointed, inner margin nearly straight; origin situated posterior to pectoral-fin insertion by about a third of the pectoral-fin inner margin length, midpoint of base 1.72 (1.93–2.68) times closer to pectoral insertions than pelvic origins; free rear tip anterior to pelvic-fin origins by about an eye length; posterior margin arching posteroventrally from apex, then abruptly to near free tip; insertion posterior to dorsal-fin apex. First dorsal fin base 2.24 (1.91–1.96) in interdorsal space, 2.50 (2.51–2.66) in dorsal caudal margin; height 1.21 (1.13–1.34) in base; inner margin 2.07 (1.68–1.89) in height, 2.52 (1.90– 2.54) in base.

Second dorsal fin very small and low, subtriangular; height 4.16 (3.21–4.45) in first dorsal-fin height, base 2.52 (2.78–3.07) in first dorsal-fin base; anterior margin weakly convex; apex rounded; posterior margin weakly concave; free rear tip long, acutely pointed, inner margin

https://doi.org/10.1371/journal.pone.0209387.g005

nearly straight; origin opposite anal-fin midbase ( Fig 8 View Fig 8 ); rear tip well behind anal-fin free rear tip, in front of upper caudal-fin origin by 1.36 (0.43–1.00) times its inner margin; posterior margin directed strongly posteroventrally from apex; insertion about opposite fin apex. Second dorsal fin base 2.02 (1.56–1.82) in dorsal–caudal space; height 2.01 (1.40–1.81) in base; inner margin 1.71 (1.28–1.98) times height, 1.17 (0.91–1.09) in base.

Anal fin apically narrow and strongly falcate; slightly larger than second dorsal fin; height 1.49 (1.17–1.25) times second dorsal-fin height, base length 1.21 (1.11–1.17) times second dorsal-fin base; anterior margin moderately convex; apex narrowly rounded; posterior margin deeply notched at slightly less than a right angle; free rear tip acutely pointed, inner margin nearly straight; origin well anterior to second dorsal-fin origin; insertion about level with second dorsal-fin midbase, anterior to fin apex; free rear tip in front of lower caudal-fin origin by a length slightly more than its inner margin length; posterior margin slanting anterodorsally and then abruptly posterodorsally. Anal-fin base expanded anteriorly as very short preanal ridges (obscure), less than a quarter length of rest of base. Anal-fin base 1.77 (1.47–1.55) in anal–caudal space; height 1.64 (1.40–1.60) in base; inner margin 1.18 (1.28–1.52) times height, 1.38 (1.05–1.09) in base.

Caudal fin narrow-lobed and asymmetrical, with short terminal lobe and prominent but moderately long, non-falcate ventral lobe; dorsal caudal margin proximally and distally convex, and slightly concave just anterior to subterminal notch, with prominent lateral undulations; preventral margin moderately convex, tip of ventral caudal-fin lobe narrowly rounded; lower postventral margin weakly concave; upper postventral margin straight; subterminal notch a narrow, deep slot; subterminal margin nearly straight; terminal margin irregular and weakly concave, lobe formed by these margins angular, tip of tail narrowly rounded. Length of dorsal caudal margin 2.98 (2.35–2.54) in precaudal length, preventral caudal margin 2.28 (2.35–2.66) in dorsal caudal margin, terminal lobe from caudal tip to subterminal notch about 3.15 (3.19–3.62) in dorsal caudal margin, subterminal margin length 1.57 (2.14–2.24) in terminal margin.

Counts of total vertebral centra ( TC) 120 (117–118), precaudal centra (PC) 54 (58), monospondylous precaudal ( MP) centra 36 (39–40), diplospondylous precaudal ( DP) centra 18 (18– 19), diplospondylous caudal ( DC) centra 66 (59–60); MP centra 30 (34.2)%, DP centra 15 (15.4–16.7)%, and DC centra 55 (49.1–50.4)% of TC centra. Ratios of DP/ MP centra 0.50 (0.45–0.49), DC/ MP centra 1.83 (1.44–1.48).

Colour. In preservative: dorsal surface of head, trunk and tail grey, graduating to pale ventral colouration on midlateral surfaces. Demarcation between light and dark surfaces of head strong (light ventral colour just visible in dorsoventral view of head), extending along lateral angle of the snout anteriorly to level of nostrils, extending dorsoposteriorly to level of upper margin of eye; then extending very gradually ventroposteriorly to about upper edge of first gill slit; waterline more diffuse over gills, almost at level of upper margins; gill slit membranes mostly pale; margins of gill slits narrowly pale edged. Demarcation between dorsal and ventral coloration becoming diffuse above pectoral fins; extending diffusely along abdomen and tail at about midlateral level; pale area continuing onto base of caudal fin. Fins without any obvious dark or light markings. First dorsal fin grey, lower margin of free tip pale. Second dorsal grey, posterior margin slightly paler. Anal fin slightly paler grey. Caudal fin grey, terminal and ventral lobes slightly darker. Pectoral fins grey on both surfaces, posterior margins diffusely paleedged. Pelvic fins pale grey, much paler on ventral surfaces basally. Eyes blackish; nictitating membrane pale.

Size

Only known from the three type specimens, a late-term embryo 339 mm TL and two juvenile females 370 and 433 mm TL. Size at birth likely close to 340 mm TL, since late-term embryo was fully developed and 370 mm TL juvenile had a faint umbilical scar.

Distribution

Uncertain; collection records indicate southern South China Sea (Gulf of Thailand, Vietnam, Malaysian Borneo).

Etymology

The specific name is Latin for ‘extinct’ ( obsolerus ) in allusion to the fact that the species has not been recorded in many decades. Proposed English vernacular name: Lost Shark.