Stegonotus, Dumeril, 1854

O’Shea, Mark & Richards, Stephen J., 2021, A striking new species of Papuan groundsnake (Stegonotus: Colubridae) from southern Papua New Guinea, with a dichotomous key to the genus in New Guinea, Zootaxa 4926 (1), pp. 26-42 : 36-37

Key to the fourteen species of Stegonotus currently recognised from the New Guinea region, and two species from adjacent areas that might occur in the southern regions of New Guinea

New Guinea species in bold. PNG = Papua New Guinea; ID = Indonesia (western New Guinea); AU = Australia.

1a Body dorsally with dark posterior edging to each scale, producing a distinctive reticulate pattern; distribution: d’Entrecasteaux Archipelago, Milne Bay Prov., and mainland PNG; Schouten Islands, Papua Prov., ID..................... S. reticulatus

1b Body patterning not as above........................................................................... 2

2a Head dark, contrasting with white body, the latter often with scattered dark scales that increase in frequency posteriorly after midbody............................................................................................ 3

2b Body patterning not as above............................................................................ 4

3a Dorsal scales in 17-17-15 or 17-19-15 rows; ventrals fewer than 215; infralabials 10; distribution: Raja Ampat Islands; West Papua Prov., ID.................................................................................. S. iridis

3b Dorsal scales in 17-19-15 or 19-19-15 rows; ventrals more than 225; infralabials 8–9; distribution: Gulf Prov., PNG.............................................................................................. S. aplini sp. nov.

4a Dorsal scales in 19 rows at midbody...................................................................... 5

4b Dorsal scales in 15 or 17 rows at midbody.................................................................. 6

5a Ventral scales 200 or fewer; fewer than 80 subcaudals; nine supralabials with 4 th to 6 th in contact with the orbit; rostral Ushaped; distribution: Madang Prov., PNG........................................................... S. poechi

5b Ventral scales more than 200; more than 90 subcaudals; eight supralabials with 4 th and 5 th in contact with the orbit; distribution: Admiralty Islands, Manus Prov., PNG........................................................ S. admiraltiensis

6a Dorsal scales in 15-15-15 or 15-15-13 rows................................................................ 7

6b Dorsal scales in 17-17-15 rows......................................................................... 10

7a Seven supralabials, with 3 rd and 4 th in contact with the orbit; eight infralabials, with 1 st to 4 th, or 1 st to 5 th in contact with anterior genials.............................................................................................. 8

7b Seven or eight supralabials; nine or ten infralabials, with 1 st to 5 th in contact with anterior genials...................... 9

8a Ventral scales fewer than 188; subcaudals fewer than 80; 1 st to 4 th infralabials in contact, not dark grey or black, with anterior genials, not dark grey or black; distribution: north of Central Cordillera, PNG and ID......................... S. diehli

8b Ventral scales more than 175; subcaudals more than 85; 1 st to 5 th infralabials dark grey to black, in contact with anterior genials; distribution: Simbu, Southern Highlands and Hela Provs., PNG................................... S. melanolabiatus

9a Ten infralabials, with 1 st to 5 th in contact with anterior genials; ventral scales more than 200; subcaudals more than 80; 8 supralabials with 4 th and 5 th in contact with orbit; distribution: Madang Prov., PNG........................... S. dorsalis

9b Nine infralabials, with 1 st to 5 th in contact with anterior genials; ventral scales fewer than 200; subcaudals 80 or fewer; 7 supralabials, with 3 rd and 4 th in contact with orbit, or 8 with 4 th and 5 th in contact with orbit; distribution: d’Entrecasteaux and Trobriand Islands, Milne Bay Prov., PNG......................................................... S. guentheri

10a Seven supralabials, with 3 rd and 4 th in contact with orbit...................................................... 11

10b Eight or nine supralabials, with 4 th and 5 th in contact with orbit................................................ 15

11a Eight or nine infralabials, with 1 st to 4 th in contact with anterior genials.......................................... 12

11b Eight or nine infralabials, with 1 st to 5 th in contact with anterior genials.......................................... 13

12a Subcaudals, single, fewer than 100; rostral visible from above; distribution: Bismarck Archipelago, PNG...... S. heterurus

12b Subcaudals paired, more than 100; rostral not visible from above; distribution: Aru Islands, ID................ S. aruensis

13a Ventral scales fewer than 175; rostral not visible from above; distribution: Schouten Islands , Papua Prov., ID..... S. parvus

13b Ventral scales more than 177........................................................................... 14

14a Subcaudals fewer than 95; infralabials white or cream; distribution: Raja Ampat Islands, West Papua Prov., ID...................................................................................................... S. derooijae

14b Subcaudals more than 85; infralabials dark grey or black; distribution: Simbu, Southern Highlands and Hela Provs., PNG........................................................................................ S. melanolabiatus

15a Ventrals more than 200................................................................................ 16

15b Ventrals fewer than 200............................................................................... 17

16a Subcaudals more than 80; eight or nine supralabials, with 4 th and 5 th in contact with orbit; nine infralabials; distribution: Bird’s Head Peninsula, West Papua Prov., ID........................................................... S. cucullatus

16b Subcaudals fewer than 90; eight supralabials, with 4 th and 5 th in contact with orbit; eight, nine or ten infralabials; distribution: Torres Strait Islands, Queensland, AU............................................................. S. australis

17a Subcaudals fewer than 100; seven to nine supralabials, with 3 rd and 4 th in contact with orbit; distribution: Raja Ampat Islands, West Papua Prov., ID......................................................................... S. derooijae

17b Subcaudals more than 100; seven supralabials, with 3 rd to 5 th in contact with orbit; distribution: Bird’s Head Peninsula, West Papua Prov., ID.............................................................................. S. ayamaru