Glaucostegus Bonaparte, 1846 Link

Habib, Kazi Ahsan & Islam, Md Jayedul, 2021, Description of a new species of giant guitarfish, Glaucostegus younholeei sp nov. (Rhinopristiformes: Glaucostegidae) from the northern Bay of Bengal Bangladesh, Zootaxa 4995 (1), pp. 129-146 : 141

Key to the species of Glaucostegus Bonaparte, 1846 Link

A definition of the genus Glaucostegus was provided by Last et al. (2016b).

1a. Snout tip expanded into a club-like knob................................................... Glaucostegus thouin

1b. Snout tip not expanded into a club-like knob................................................................ 2

2a. Snout obtuse, tip broadly rounded, angle ~80°; nostrils almost twice in mouth width; one small spiracular fold.... G. obtusus

2b. Snout tip bluntly pointed or narrowly rounded, angle ~31–65°.................................................. 3

3a. Orbit diameter 5–7.8 in preorbital length................................................................... 4

3b. Orbit diameter 8–16 in preorbital length................................................................... 6

4a. Orbit diameter 5–6 in preorbital length, 1.5–2 in interorbital space; nostrils 1.4 ininternasal width; nasal lamellae ~81;.............................................................................................. G. cemiculas

4b. Orbit diameter 6.3–7.8 in preorbital length, 2.1–4 in interorbital space........................................... 5

5a. Orbit diameter 2.1–2.7 in interorbital space; nostril 1.2–1.3 in internasal width; nasal lamellae ~61.............. G. halavi

5b. Orbit diameter 4 in interorbital space; nostril 0.33 in internasal width...................................... G. petiti

6a. Nostrils almost as wide as mouth, 2.2–2.4 in internasal width; orbit diameter 6.1–7.8 in preorbital length, 1.8–2.4 in interorbital space......................................................................................... G. typus

6b. Nostrils moderately large, about half of the mouth width, subequal to internasal space............................... 7

7a. Snout tip bluntly pointed, angle 46–52°; orbit diameter 9–16 in preorbital length; at least ~ 2290 mm total length in matured males................................................................................... G. granulatus

7b. Snout tip more pointed, angle 31–40°; orbit diameter (adults) 8.2–11.6 in preorbital length; at least ~ 730 mm total length in matured males.............................................................................. G. younholeei