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| Carcharhinus obsolerus
White, Kyne & Harris, 2019
Lost Shark || DOI: 10.1371/journal.pone.0209387
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Abstract
Carcharhinus obsolerus is described based on three specimens from Borneo, Thailand and Vietnam in the Western Central Pacific. It belongs to the porosus subgroup which is characterised by having the second dorsal-fin insertion opposite the anal-fin midbase. It most closely resembles C. borneensis but differs in tooth morphology and counts and a number of morphological characters, including lack of enlarged hyomandibular pores which are diagnostic of C. borneensis. The historic range of C. obsolerus sp. nov. is under intense fishing pressure and this species has not been recorded anywhere in over 80 years. There is an urgent need to assess its extinction risk status for the IUCN Red List of Threatened Species. With so few known records, there is a possibility that Carcharhinus obsolerus sp. nov. has been lost from the marine environment before any understanding could be gained of its full historic distribution, biology, ecosystem role, and importance in local fisheries.
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| Fig 1. Lateral view of Carcharhinus obsolerus sp. nov. (NMW 61463; female holotype 433 mm TL). A. Preserved specimen; B. Painting by Lindsay Marshall (www.stickfigurefish.com.au). |
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| Fig 2. Head of Carcharhinus obsolerus sp. nov. (NMW 61463; Holotype). 433 mm TL female: A. lateral view; B. ventral view. |
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| Fig 5. In situ teeth of Carcharhinus obsolerus sp. nov. (ANSP 77121, paratype). 370 mm TL female: A. upper teeth; B. lower teeth. |
Carcharhinus obsolerus White, Kyne & Harris sp. nov.
Synonymy: Carcharhinus sp.: [Compagno, 1979]: 517, 520, 523, 536 (Borneo); [Compagno, 1988]: 319, 321, 327 (Vietnam, Borneo, and Thailand); [Compagno et al., 1998]: 1359, fig (Vietnam, Borneo, and Thailand)
Carcharhinus porosus: [Compagno et al., 2005]: 71 (Borneo, Saigon, and Bangkok)
Carcharhinus undescribed small species: [Compagno, 1984]: 497 (Borneo, Vietnam, and Thailand)
Carcharhinus sp. (= ‘Carcharhinus porosus’): [Compagno et al., 1998]: 1322.
Carcharhinus sp. A: [Compagno et al., 2005]: 307, fig, pl. 62 (Borneo, Vietnam, and Thailand); [Voigt et al., 2011]: 103, fig 50
Holotype: NMW 61463, female 433 mm TL, Bangkok, Thailand, no date or collector recorded.
Paratypes: ANSP 76859, female late-term embryo 339 mm TL, Ho Chi Minh City, Vietnam, Dec. 1934, coll. H. Rutherfurd; ANSP 77121 (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.
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Distribution: Uncertain; collection records indicate southern South China Sea (Gulf of Thailand, Vietnam, Malaysian Borneo).
The distribution of Carcharhinus obsolerus is uncertain. Given that this species has not been seen in many decades, a better understanding of the distribution of this species is unlikely unless archaeological or paleontological records are found. While Baram in Sarawak is likely an accurate collection locality, both Bangkok and Ho Chi Minh City specimens may have been caught in other South-east Asian locations and brought into these cities where bigger markets exist. Thus, there is a possibility it had a much more restricted distribution than the three known specimens allude to, but it cannot be ruled out that it had a wider distribution in the South-east Asian region.
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.
William T. White, Peter M. Kyne and Mark Harris. 2019. Lost before Found: A New Species of Whaler Shark Carcharhinus obsolerus from the Western Central Pacific known only from Historic Records. PLoS ONE. 14(1): e0209387. DOI: 10.1371/journal.pone.0209387
