Pseudotriakidae

Weigmann, Simon, Stehmann, Matthias F. W. & Thiel, Ralf, 2013, Planonasus parini n. g. and n. sp., a new genus and species of false cat sharks (Carchariniformes, Pseudotriakidae) from the deep northwestern Indian Ocean off Socotra Islands, Zootaxa 3609 (2), pp. 163-181 : 179-180

Key to the species of the family Pseudotriakidae

1 Maximal total length about 3 m, size at birth well above 1 m TL, first dorsal fin very long, low, and keel-like, much longer and much lower than second dorsal fin, caudal peduncle short, more than 200 tooth rows per jaw...................................................................................... Pseudotriakis microdon (patchy, almost world-wide)

- Maximal total length less or only slightly more than 1 m, first dorsal fin not low and keel-like, at least moderately angular and high, about as long as second dorsal fin, caudal peduncle long, far fewer than 200 tooth rows per jaw.................. 2

2 Body soft, lateral trunk denticles loosely set, heterodonty distinct, oral papillae present, spiracles large, mouth large, its width 0.8–1.0 times head width, head length about 3 times in precaudal length, first dorsal fin longer than second dorsal fin at least in larger specimens, its height 0.6–0.7 times second dorsal fin height, second dorsal fin not falcate, interdorsal space small, shorter than second dorsal fin total length, total vertebral centra 115–140, about 110–115 tooth rows in upper jaw......................................................................... Planonasus parini (northwestern Indian Ocean)

- Body at least rather firm, lateral trunk denticles densely set, heterodonty weak, no oral papillae, spiracles small, mouth smaller, its width 0.7–0.8 times head width, head length about 4 times in precaudal length, first dorsal fin shorter than second dorsal fin, its height subequal to second dorsal fin height, second dorsal fin falcate, interdorsal space large, longer than second dorsal fin total length, total vertebral centra 151–168, about 94–99 tooth rows in upper jaw................................... 3

3 Abrupt lateral demarcation of relatively dark dorsal surface and whitish ventral surface (more distinct in fresh specimens), white posterior margins at all fins, ventral head and mouth pale, anal fin with concave posterior margin, preoral length exceeding mouth width, eye length 1.8–1.9 times nostril width, internarial space 1.8–1.9 times nostril width, prenarial length 2.8–2.9 times subterminal caudal margin length, total vertebral centra 162–168................................................................................................................ Gollum attenuatus (southwestern Pacific)

- Body plain brown dorsally and dusky ventrally with some whitish patches, anal and dorsal fins with translucent dusky posterior margins, ventral head and mouth dark, anal fin with straight posterior margin, preoral length shorter than mouth width, eye length 1.4–1.5 times nostril width, internarial space 1.5 times nostril width, prenarial length 1.6–2.1 times subterminal caudal margin length, total vertebral centra 151–154.................................... G. s ul uen si s (Sulu Sea, Philippines)