Thai National Parks

Snakes of Thailand

Species of Thailand

Graceful Small-headed sea snake

In Thai: งูคออ่อนหัวเข็ม, ngu khor oon hua khem

Binomial name: Hydrophis gracilis, George Shaw, 1802

The Graceful Small-headed Sea Snake or Slender Sea Snake Hydrophis gracilis is a species of Elapidae (Hydrophiinae-sea snake). Microcephalophis gracilis is a synonym of the snake.

Diagnostic characters

Head small, body long and slender anteriorly; scales on thickest part of body juxtaposed; 5-6 maxillary teeth behind fangs; 17-21 scale rows around neck, 30-36 around thickest part of body (increase from neck to midbody 18-24); ventrals divided by a longitudinal fissure; prefrontal in contact with third upper labial; ventrals 220-287.

Total length males 950 mm, females 1025 mm; tail length males 80 mm, females 95 mm.


  • Indian Ocean (Pakistan, India, Bangladesh, Myanmar, Thailand, Philippines)
  • South China Sea northward to the coast of Fujian (China)
  • Persian Gulf to Bay of Bengal (Oman, United Arab Emirates, Iran)
  • Coast of Malaysia through Indoaustralian Archipelago to New Guinea, New Caledonia, Australia (Queensland), Melanesia, Indonesia

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Scientific classification

Hydrophis gracilis

Common names

  • English:
    • Graceful small-headed sea snake
    • Graceful sea snake
    • Slender sea snake
    • Common small-headed sea snake
  • Thai: งูคออ่อนหัวเข็ม, ngu khor oon hua khem


  • Microcephalophis gracilis, Van Stanley Bartholomew Wallach et al. (2014)
  • Hydrophis gracilis, Arne Redsted Rasmussen et al. (2011)
  • Hydrophis gracilis, T.S.N. Murthy (2010)
  • Hydrophis gracilis, Nguyen Van Sang et al. (2009)
  • Hydrophis gracilis, Allen Eddy Greer (2006)
  • Microcephalophis gracilis microcephalus, Vladimir Emelyanovich Kharin (2005)
  • Hydrophis gracilis, Patrick David et al. (2004)
  • Hydrophis (Microcephalophis) gracilis, Vladimir Emelyanovich Kharin (2004)
  • Hydrophis gracilis, Alan E. Leviton et al. (2003)
  • Microcephalophis gracilis, Wolfgang Grossmann & Frank Tillack (2001)
  • Hydrophis gracilis, Harold Cogger (2000)
  • Microcephalophis gracilis, Indraneil Das (1996)
  • Hydrophis gracilis, Kenneth R. G. Welch (1994)
  • Hydrophis gracilis, Aaron Matthew Bauer & Jens V. Vindum (1990)
  • Microcephalophis gracilis, Malcolm Arthur Smith (1943)
  • Microcephalophis gracilis gracilis, Malcolm Arthur Smith (1926)
  • Microcephalophis gracilis, Frank Wall (1921)
  • Hydrophis rostralis, Malcolm Arthur Smith (1917)
  • Distira gracilis, Frank Wall (1909)
  • Hydrophis gracilis, George Albert Boulenger (1896)
  • Hydophis guntheri, James A. Murray (1884)
  • Hydrophis gracilis, Albert Charles Lewis Günther (1864)
  • Hydrophis leprogaster, André Marie Constant Duméril & Gabriel Bibron in Johann Gustav Fischer (1856)
  • Hydrophis gracilis, Johann Gustav Fischer (1856)
  • Hydrophis microcephala, Johann Gustav Fischer (1856)
  • Hydrophis gracilis, André Marie Constant Duméril, Gabriel Bibron & Auguste Duméril (1854)
  • Hydrophis microcephalus, André Marie Constant Duméril, Gabriel Bibron & Auguste Duméril (1854)
  • Thalassophis microcephala, Karl Patterson Schmidt (1852)
  • Microcephalophis gracilis, René-Primevère Lesson (1834)
  • Hydrus kadellnagam, Friedrich Boie (1827)
  • Disteira gracilis, Leopold Fitzinger (1826)
  • Hydrus gracilis, George Shaw (1802)


No photo for this species yet

Range Map

Distribution map of Graceful Small-headed sea snake, Hydrophis gracilis in Thailand
  • Phuket Coast
Range map of Hydrophis gracilis in Thailand