Atractus

Passos, Paulo, Mueses-Cisneros, Jonh Jairo, Lynch, John D. & Fernandes, Ronaldo, 2009, Pacific lowland snakes of the genus Atractus (Serpentes: Dipsadidae), with description of three new species, Zootaxa 2293, pp. 1-34 : 29-30

Key to Pacific lowlands species of Atractus

1. Contact between symphisial and chinshield scales, dorsum and belly entirely black ...................................... A. melas

- First pair of infralabials preventing symphisial/chinshields contact, dorsum and belly never uniformly black .......... 2

2. 15/15/15 dorsal scale rows............................................................................................................................................ 3

- 17/17/17 dorsal scale rows............................................................................................................................................ 4

3. Ventrals in males more than 155, subcaudals more than 45, dorsum with dark bands and light interspaces of similar size along body .............................................................................................................................................. A. typhon

- Ventrals in males, fewer than 130, subcaudals fewer than 40, dorsum with irregular blotches decreasing in size pos- teriorly.......................................................................................................................................................... A. echidna

4. First two infralabials contacting chinshields, venter light with dark dots restricted to lateral portion of ventral scales forming paraventral lines ................................................................................................................... A. microrhynchus

- First three or four infralabials contacting chinshields, venter creamish white or black but never having dark dots restricted to lateral portion of ventrals forming paraventral lines- ............................................................................... 5

5. Venter heavily pigmented, at least posterior region uniformly black ........................................................................... 6

- Venter uniformly creamish white, occasionally with small black dots concentrated on posterior region of body but never entirely black....................................................................................................................................................... 7

6. Preocular scales absent, 135–144 ventrals and 25–37 subcaudals in females, 135–143 ventrals and 33–38 subcaudals in males ...................................................................................................................................................... A. iridescens

- Preocular scales occasionally present, 169–190 ventrals and 31–38 subcaudals in females, 169-175 ventrals 43–45 subcaudals in males .................................................................................................................................... A. paucidens

7. Dorsal ground colour light with round dark blotches paired on paravertebral region and decreasing in size posteriorly ................................................................................................................................................................................ 8

- Dorsal ground colour dark with alternating light transversal bands reaching paraventral region of flanks along all of body length, bands sometimes attain similar size to light interspaces.......................................................................... 9

8. 180–189 ventrals, two postdiastemal teeth, venter immaculate creamish white ..................................... A. boulengerii

- 33 ventrals, single postdiastemal tooth, venter with dark brown dots posteriorly ....................................... A. medusa

9. 177–183 ventrals in males, dorsal ground colour beige with dark brown bands similar in size to light interspaces, venter immaculate creamish white .......................................................................................................... A. multicinctus

- 153–165 ventrals in males, dorsal ground colour black with thin transversal light bands, venter with dark pigmentation invading lateral portion of ventral scales .................................................................................................. A. clarki .