Key to Species of the genus Gonorhynchus

A dichotomous key was constructed for Gonorhynchus based on data collected here and characters reported in Menon & Jacob (1996) for G. periyarensis . Species distributions by river basin are provided in parentheses after species names.

1 Triangular rostral flaps present on tip of snout......................................... G. bicor nis (Salween River)

- Rostral flaps absent................................................................................... 2

2 Large specimens (> 65 mm SL) with tubercles on snout and cheeks............................................. 3

- Large specimens without tubercles....................................................................... 4

3 15–17 rakers on first gill arch, tubercles only on cheeks and snout....................... G. periyarensis (Periyar River)

- 20–24 rakers on first gill arch, tubercles on head, occasionally extending onto humeral, breast, and predorsal regions.......................................................................... G. wattanah (Bhima and Godavari Rivers)

4 Thick midlateral stripe coloring entirety of midlateral scales and partially coloring scales above and below; dorsolateral spots, if present, form uniform reticulated pattern; crescent-shaped spot present on 5th–6th lateral-line scales and extending onto ante- rior halves of scales above and below................................ G. burmanicus (Irrawaddy and Salween Rivers)

- Thick midlateral stripe absent, although thin stripe (less than one scale wide) may be present; dorsolateral spots, if present, forming irregular patches, not uniform reticulated pattern; crescent-shaped spot occasionally present on 5th–6th lateral-line scale.................................................................................................... 5

5 Total lateral-line scales 40 (rarely 36–38); restricted to drainages of the Bay of Bengal................................................................... G. latius (Ganges, Brahmaputra, Meghna, Subarnarerkha, and Mahanadi Rivers)

- Total lateral-line scales 35–38; restricted to drainages of the Arabian Sea and the Gulf of Oman, and inland endorheic basins in Afghanistan and Iran .................................................................................. 6

6 Rostral fold without fringes....................................................... G. macmahoni (Dasht River)

- Rostral fold with fringes........ G. diplochilus (Indus, Sistan, and Helmand Rivers; coastal drainages of the Gulf of Oman)