Bythaelurus vivaldii Weigmann & Kaschner, 2017
Vivaldi’s catshark
photo by Weigmann, S.

Family:  Pentanchidae (Deepwater catsharks)
Max. size:  32.5 cm TL (female)
Environment:  pelagic-oceanic; marine; depth range - 628 m
Distribution:  Western Indian Ocean: Off Somalia.
Diagnosis:  This species is distinguished by the following characters: body firm and stout (of the presumably adult holotype and slender in supposedly juvenile paratype); snout is long (preorbital length 6.1-6.6% TL) and broad, bell-shaped in dorsoventral view with a distinct lateral indention; the pre-outer nostril length is subequal to internarial space; preorbital snout length is subequal to interorbital space; preoral snout length 1.4–1.8 times in mouth width; eye length 13.9-15.0 times in predorsal distance, 6.8-6.9 times in head length and 1.6-2.3 times eye height; head length 2.6-2.8 times width at level of maximum outer extent of anterior nostrils; head width at the level of maximum outer extent of anterior nostrils, 1.2 times width at level of lateral indention of head, 1.3–1.4 times preorbital length, and 8.5–8.6% TL; the roof of the mouth is loosely set with rather small, knob-like to elongated oral papillae, oral papillae on tongue hardly detectable; pelvic-fin anterior margin 2.0-2.1 times in pectoral-fin anterior margin; first dorsal-fin base 2.2-2.3 times in interdorsal space; length of second dorsal-fin inner margin 1.3-2.3 times in second dorsal-fin height; second dorsal-fin base length 5.3% TL; anal-fin base 0.7-0.8 times interdorsal space; upper jaw with 68-75 and lower jaw with 64 rows of small tri- to pentacuspidate teeth with outer surface of crown furrowed by strong longitudinal ridges from base of cusps to tip and strongly structured by reticulations from basal areas to well into cusps; monospondylous trunk vertebrae centra 38, diplospondylous precaudal centra 43-44, total centra about 135-140; dermal denticles leaf-like to teardrop-shaped on snout and tricuspidate on trunk and tail; reported to have 8–9 dark, broad but inconspicuous transverse bars on the back (preserved coloration plain beige with scattered remains of dark brown); .

Description: The new species is distinguished from all congeners in the western Indian Ocean by having a larger pre-second dorsal fin length, a longer head, a larger interdorsal space, a larger intergill length, a longer pectoral-fin posterior margin, a shorter caudal fin, an intermediate caudal fin preventral margin, and a larger internarial width (Ref. 114990).

IUCN Red List Status: Data deficient (DD); Date assessed: 22 November 2019 Ref. (126983)
Threat to humans:  harmless

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