Bach's Catshark

description

Description of the holotype (Figures 2 – 18). Values of the paratypes in parentheses. Morphometric measurements and meristics are given in Table 1. External morphology. Body firm and stout (slender in juveniles), subcircular in cross section at mid-trunk, laterally compressed and tapering posterior to cloaca; head region broad, long abdominal and caudal sections (Figures 2 – 4). No predorsal, interdorsal, or postdorsal ridges; no postanal ridge; no lateral ridges on caudal peduncle. Trunk about as long as tail, distance from tip of snout to anterior cloaca 51.6 % TL (42.0 – 53.2 % TL, small values in post-embryos and small juveniles only, details can be found under Remarks); pre-first dorsal-fin length 50.1 % TL (41.1 – 51.9 % TL, small values in post-embryos and small juveniles only), pre-second dorsal-fin length 65.5 % TL (56.4 – 66.7 % TL, small values in post-embryos and small juveniles only), ventral precaudal length 71.7 % TL (61.7 – 72.8 % TL, small values in post-embryos and small juveniles only). Head broad and dorsoventrally flattened, with a broadly rounded snout; laterally slightly compressed in gill region (Figure 5); no supraorbital crests on chondrocranium; head leng

Bythaelurus bachi n. sp., a new deep-water catshark (Carcharhiniformes, Scyliorhinidae) from the southwestern Indian Ocean, with a review of Bythaelurus species and a key to their identification

description

Figures 2 – 18; Tables 1 – 2 Holotype ZMH 26160, adult male, 422 mm TL fresh, 390.5 mm TL 70 % ethanol preserved, RV ‘ Vityaz’, cruise 17, station 2707, Walters Shoals, 33 ° 01.8 ’ S, 44 ° 23.6 ’ E – 32 ° 59.8 ’ S, 44 ° 24.4 ’ E, 910 – 925 m depth, 19.4 m shrimp trawl, trawl # 60, on the bottom for 60 minutes, 15 Dec 1988. Paratypes (43) ZMH 26161, adult female with one egg case in each uterus, 405 mm TL fresh, 395 mm TL 70 % ethanol preserved, RV ‘ Vityaz’, cruise 17, station 2668, Walters Shoals, 33 ° 01.2 ’ S, 44 ° 36.8 ’ E – 33 ° 05.2 ’ S, 44 ° 39.2 ’ E, 1010 m depth, 19.4 m shrimp trawl, trawl # 48, on the bottom for 61 minutes, 0 8 Dec 1988; ZMH 26162, female post-embryo, 122 mm TL fresh, 120 mm TL 70 % ethanol preserved, data the same as ZMH 26161; ZMH 26163, juvenile female, 227 mm TL fresh, 220 mm TL 70 % ethanol preserved, data the same as ZMH 26161; ZMH 26164, juvenile female, 361 mm TL fresh, 355 mm TL 70 % ethanol preserved, data the same as ZMH 26161; ZMH 26165, juvenile male, 210 mm TL fresh, 205 mm TL 70 % ethanol preserved, data the same as ZMH 26161; ZMH 26166, juvenile male, 248 mm TL fresh, 240 mm TL 70 % ethanol preserved, data the same as ZMH 26161; ZMH 26167,

Bythaelurus bachi n. sp., a new deep-water catshark (Carcharhiniformes, Scyliorhinidae) from the southwestern Indian Ocean, with a review of Bythaelurus species and a key to their identification

diagnosis

Diagnosis. A small scyliorhinid and a medium-sized Bythaelurus species with the following characteristics: body firm and stout (slender in juveniles); snout long (preorbital length 4.7 – 7.6 % TL) and broad, bell-shaped in dorsoventral view with distinct lateral indention; pre-outer nostril length 1.1 – 1.9 times internarial space; preorbital snout length 0.7 – 1.0 times interorbital space; preoral snout length 1.0 – 1.9 times in mouth width; eye length 9.0 – 13.0 times in predorsal distance, 3.6 – 5.4 times in head length and 1.4 – 4.1 times eye height; head length 1.8 – 2.7 times width at level of maximum outer extent of anterior nostrils; head width at level of maximum outer extent of anterior nostrils 1.1 – 1.5 times width at level of lateral indention of head, 1.1 – 1.8 times preorbital length, and 7.2 – 10.0 % TL; tongue and roof of mouth densely set with oral papillae of distinct size, which are partially very large and conglomerated from several single papillae; pelvic anterior margin 1.1 – 2.1 times in pectoral-fin anterior margin; first dorsal-fin base 1.0 – 1.8 times in interdorsal space; length of second dorsal-fin inner margin 0.5 – 1.9 times in second dorsal-fin heigh

Bythaelurus bachi n. sp., a new deep-water catshark (Carcharhiniformes, Scyliorhinidae) from the southwestern Indian Ocean, with a review of Bythaelurus species and a key to their identification

discussion

Remarks. There are several morphometric differences between the post-embryonic, small immature, and large immature plus adult specimens of Bythaelurus bachi, which might be of ontogenetic nature. These differences are demonstrated in Table 2. As indicated in Table 2, there is strong variation in the measurements of pectoral — pelvic space among specimens> 250 mm TL, which ranges from 20.2 to 26.0 % TL in the holotype and 22 paratypes of 284 – 400 mm TL in the ZMH collection and from 26.6 to 31.6 % TL in the 12 other paratypes of 392 – 445 mm TL. Due to the geographic proximity of catch locations and individual differences in taking the measurement having been excluded, the large pectoral — pelvic space might be a characteristic of very large specimens. Nevertheless, this difference might also be influenced by the condition of the specimens.

Bythaelurus bachi n. sp., a new deep-water catshark (Carcharhiniformes, Scyliorhinidae) from the southwestern Indian Ocean, with a review of Bythaelurus species and a key to their identification