Key to the Species of Nettenchelys juveniles and adults

1 Anteriormost vomerine teeth uniserial..................................................................... 2

- Anteriormost vomerine teeth not uniserial.................................................................. 5

2 Posterior nostril located immediately behind eye............................................................. 3

- Posterior nostril approximately midway between eye and supratemporal canal..................................... 4

3 Small size, mature at 150–200 mm; PDV 7–8; PAV 40–43; PCV 75; IO pores 8+3; predorsal length 33–35% preanal, head length 30–33% preanal................................................. Nettenchelys pygmaea (western Atlantic)

- Larger size, greater than 250 mm; PDV 6; PAV 44; PCV 78; IO pores 9+2; predorsal length 31% preanal; head length 28% preanal........................................................................ Nettenchelys proxima (Taiwan)

4 Anterior vomerine teeth not enlarged; PAV 38–39.............................. Nettenchelys dionisi (eastern Atlantic)

- Anterior vomerine teeth enlarged; PAV 42–ca. 47............................. Nettenchelys gephyra (western Pacific)

5 Posterior nostril on head just in front of supratemporal canal; median ST pore present.. Nettenchelys inion (western Atlantic)

- Posterior nostril on body behind supratemporal canal; median ST pore absent..................................... 6

6 Posterior nostril about midway between dorsal-fin origin and anus................... Nettenchelys taylori (Indian Ocean)

- Posterior nostril much closer to dorsal-fin origin than to anus................................................... 7

7 Posterior nostril close to dorsal-fin origin, approximately over the eighth LL pore.............................................................................................. Nettenchelys erroriensis (northwestern Indian Ocean)

- Posterior nostril before dorsal-fin origin, approximately over the second to fourth LL pore............................ 8

8 Posterior nostril immediately behindsupratemporal canal, over second LL pore; POM pores 12; PDV 5; PAV 39................................................................................. Nettenchelys paxtoni (western Pacific)

- Posterior nostril midway between supratemporal canal and dorsal-fin origin, over fourth LL pore; POM pores 14–16; PDV 7; PAV 43–44............................................................. Nettenchelys exoria (western Atlantic)