Rhinobatos ranongensis Last, Séret & Naylor, 2019
Ranong guitarfish

Family:  Rhinobatidae (Guitarfishes)
Max. size:  64.5 cm TL (male/unsexed); 51.1 cm TL (female)
Environment:  demersal; marine; depth range 30 - 69 m
Distribution:  Eastern Indian Ocean: Andaman Sea, Myanmar and western Thailand.
Diagnosis:  This medium-sized species is distinguished by the following set of characters in adult male: disc is wedge-shaped and relatively narrow, its width 31-33% TL, length 1.3-1.4 times width; snout moderately elongate, its length 3.0–3.2 times interspiracular distance, 4.1-4.4 times interorbital width; orbit and spiracular openings are small, orbit diameter ~1.5 times spiracle length; nostrils weakly oblique, length 1.3-1.6 times internarial distance; mouth narrow, 5.4-6.0% TL; preoral length 6.3-6.9 times internarial distance; posterior nasal flaps are broad; spiracular folds 2, the outermost fold slightly taller than inner fold; ridges of rostral cartilage are almost parallel, converging anteriorly but not constricted medially; anterior cartilage is broadly sickle shaped, truncate posteriorly; gill slits and their interspaces are narrow, distance between fifth gill slits 3.0-3.2 times in ventral head length; prebranchial sensory pore system distinct, extending to just behind margin of first gill slit; postscapular sensory canal indistinct, deeply embedded, not forming shallow groove; thorn patches present on supraorbit and scapular region, and row along dorsal midline rudimentary, inconspicuous; denticles on dorsal fins are densest anteriorly, present but more sparse posteriorly; dorsal fins are small, height of first 5.4-6.2% TL; pelvic-fin inner margin subequal to its base length; interdorsal distance 2.9-3.3 times first dorsal-fin base; dorsal caudal margin 2.0-2.4 times the preventral margin; upper jaw with 68-82 tooth rows; snout angle 59-64°; pectoral radials 64-68; post-synarcual centra 172-176; nasal lamellae 47-48. Colouration: dorsal fins brownish anteriorly, dusky posteriorly; dorsal disc of adults largely uniformly brownish, no spots or obvious blotches; no large, black, teardrop marking on undersurface of snout (Ref. 123963)
Biology:  Caught individuals: males at 49.4 and 50.3 cm TL were immature and the largest female (51.1 cm TL) was most probably at late adolescent or early mature stage of development (Ref. 123963).
IUCN Red List Status: Vulnerable (VU); Date assessed: 13 May 2020 (A2d) Ref. (130435)
Threat to humans:  harmless

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