Hydrophis, Latreille, 1801

Weinell, Jeffrey L., Hooper, Errol, Leviton, Alan E. & Brown, Rafe M., 2019, Illustrated Key to the Snakes of the Philippines, Proceedings of the California Academy of Sciences 66 (1), pp. 1-49 : 25-27

Hydrophis

Key to species reported from or likely to occur in marine waters in the Philippines.

1a. Longitudinal scale rows around thickest part of body> 72.......... Hydrophis annandalei

1b. Longitudinal scale rows around thickest part of body 25–70.......................... 2

2a. Rostral scale fragmented into four or five smaller scales ( Fig. 35 ); dorsal head scales with thick- ened edges.................................................. Hydrophis anomalus

2b. Rostral scale not fragmented into four or five smaller scales.......................... 3

3a. Ventral body scales large (> 1/4 body width) on anterior part of body and small on posterior part of body.................................................. Hydrophis viperinus

3b. Ventral body scales small on both anterior and posterior parts of body.................. 4

4a. Ventral surface of body uniform yellow or white; dorsal part of body uniform dark brown or black........................................................ Hydrophis platurus

4b. Ventral surface of body not uniform yellow or white; dorsal part of body not uniform dark brown or black............................................................... 5

5a. Mental scale elongate, not triangular ( Fig. 36A )................... Hydrophis schistosus

5b. Mental scale triangular, not elongate ( Fig. 36B ).................................... 6

6a. Enlarged chin shields absent................................................... 7

6b. Enlarged chin shields present, one or two pairs.................................... 8

7a. Midbody scales in> 45 longitudinal rows around body................ Hydrophis stokesii

7b. Midbody scales in <45 longitudinal rows around body................. Hydrophis curtus

8a. Longitudinal scale rows around thickest part of body ≤ 2............... Hydrophis jerdoni

8b. Longitudinal scale rows around thickest part of body ≥ 25........................... 9

9a. Frontal scale and parietal scales more or less fragmented ( Fig. 37A )...... Hydrophis peronii

9b. Frontal scale and parietal scales unfragmented ( Fig. 37B )........................... 10 10a. Maxillary teeth behind fangs ≥ 9.............................................. 11

10b. Maxillary teeth behind fangs ≤ 8.............................................. 13

11a. Neck width divided by width at widest part of body 0.45–0.56; maxillary teeth behind fangs 14–18.................................................... Hydrophis caerulescens

11b. Neck width divided by width at widest part of body ≥ 0.57; maxillary teeth behind fangs 9–13...................................................................... 12

12a. Interspaces between black transverse dorsal bands thin, less than two scale rows wide..................................................... Hydrophis ornatus or H. inornatus

12b. Interspaces between black transverse dorsal bands broad, more than two scale rows wide.............................................................. Hydrophis lamberti

13a. Width of neck> 1/2 width of widest part of body; anterior temporal scale one......... 14

13b. One or both of the following true: (1) width of neck <1/2 width of widest part of body; (2) anterior temporal scales two................................................ 15

14a. Longitudinal scale rows around midbody 8–18 more than around neck.. Hydrophis belcheri

14b. Longitudinal scale rows around midbody 4–8 more than around neck... Hydrophis spiralis

15a. Head very small, width of neck ≤ 1/3 width of widest part of body; longitudinal scale rows around neck 17–23; ventral body scales of anterior part of body wider than adjacent scale rows; ventral body scales of posterior part of body are divided by a long longitudinal furrow................................................................... Hydrophis gracilis

15b. One or more of the following combinations of characters true: (1) head small or moderate in size, width of neck> 1/3 width of widest part of body; (2) longitudinal scale rows around neck ≥ 23; (3) ventral body scales of posterior part of body not divided by a long longitudinal furrow.......................................................................... 16

16a. Longitudinal scale rows around midbody 29–35; ventral body scales 278–325; dorsal surface of head uniformly dark brown to black............................. Hydrophis coggeri

16b. One or more of the following combinations of characters true: (1) longitudinal scale rows around midbody> 35; (2) ventral body scales> 325; (3) dorsal surface of head has yellow spot behind nostrils and yellow streak behind eye...................................... 17

17a. Anterior temporal scales one................................................. 18

17b. Anterior temporal scales two................................................. 20

18a. Ventral body scales <360; maxillary teeth behind fangs 6–8.... Hydrophis melanocephalus

18b. One or both of the following true: (1) ventral body scales ≥ 360; (2) maxillary teeth behind fangs <6.................................................................. 19

19a. Longitudinal scale rows around midbody 37–45; dorsal body scales on thickest part of body hexagonal or quadrangular........................................ Hydrophis brookii

19b. Longitudinal scale rows around midbody 31–39; dorsal body scales on thickest part of body with rounded or bluntly pointed tips................................. Hydrophis klossi

20a. Width of neck ≤ 1/2 width of widest part of body; longitudinal scale rows around midbody 12–20 more than around neck; anterior surface of body dark with pale oval spots laterally that sometimes connect as crossbands.................................. Hydrophis atriceps

20b. One or both of the following true: (1) width of neck> 1/2 width of widest part of body; (2) longitudinal scale rows around midbody <12 more than around neck; (3) anterior and posterior surface of body dark with distinct white annuli............................ 21

21a. Head yellowish or olive (adults) or black (juveniles); ventral body scales with a black longitudinal stripe that may fade with age; ventral body scales 290–390... Hydrophis cyanocinctus

21b. Head black; ventral body scales usually black; ventral body scales 314–356; [non-marine] endemic to Lake Taal (Luzon).................................... Hydrophis semperi

Figures

FIGURE 35. Rostral scale fragmented into four or five scales in Hydrophis anomalus (specimen number unknown; a redrafting by EH of original image in Rasmussen et al. 2011). Rostral scale (reddish brown). Fig. 35, modified original line drawing reproduced with permission of A. Rasmussen and Zootaxa and Magnolia Press.

FIGURE 36. Ventral view of head of (A) Hydrophis schistosus (specimen number unknown; a redrafting by EH of orig- inal image in Rasmussen et al. 2011), (B) Hydrophis curtus (KU 40063). Mental scale (green), and either elongate (A) or triangular (B). Fig. 36A modified original line drawing reproduced with permission of A. Rasmussen and Zootaxa and Magnolia Press.

FIGURE 37. Dorsal view of head of (A) Hydrophis peronii (CAS 136104; a redrafting by EH of original image in Leviton et al. 2014), (B) Hydrophis melanocephalus (KU 94556). Frontal scales (green), parietal scales (purplish-gray). Fig. A reproduced and modified with permission of A. Leviton and the Calfornia Academy of Sciences.