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Family : DICROGLOSSIDAE
Species : Limnonectes megastomias
Size (snout to vent) :
Females to 86 mm, males to 124 mm
(McLeod, 2008)

Limnonectes megastomias (Big-mouthed Fanged Frog, Khorat Big-mouthed Frog) was formerly treated as a form of Limnonectes kuhlii but is now widely recognised as a separate species within the L. kuhlii complex (McLeod, 2008). 

In terms of genetics, Limnonectes megastomias is considered to have more than 18% 'sequence divergence' from true L. kuhlii which are smaller, have different relative finger lengths, and only occur on the island of Java (McLeod, 2008).

Limnonectes megastomias is endemic to eastern Thailand; in his study McLeod (2008) includes specimens from Loei, Sa Kaew and Nakhon-Ratchasima provinces. The latter province includes most of the land area of Khao Yai National Park.

This is primarily a forest stream-dwelling frog, which ranges from lowlands to 1460 metres elevation. Preferred streams have a sandy or silty substrate, with accumulated leaf litter under which to hide. They predate upon insects, other frogs, and also small birds (McLeod, 2008).

Male and female Limnonectes megastomias are sexually dimorphic. Males have thickened and elongated odontoid processes or 'fangs' on the lower jaw (such 'fangs' are a defining feature of frogs in the family Dicroglossidae). In comparison to other species in the genus, Limnonectes megastomias species is large-bodied, and males have a greatly enlarged head compared to females (up to 56% of snout-vent-length in males, compared to 45% in females) (McLeod, 2008).

McLeod described the (male) holotype as follows: "Dorsum olive-brown with dark brown blotch over shoulders and indistinct, dark transverse bars on upper surface of hind limbs; side of head and lateral surfaces of body yellowish brown; chin brownish white; belly white with brown vermiform markings; dark brown bar between eyes bordered by thin yellowish-brown bars; lower half of iris gold, upper half brown, separated by dark brown horizontal band; nuptial pad white."

The enlarged head and mouth in males appears to be used in combat with other males; some specimens studied by McLeod had "missing digits and limbs, fresh bite marks, and scars". Hiroshi & Matsui (2002) studied large-bodied male-male agonistic combat in a related species in the L. kuhlii complex from Taiwan (as Rana kuhlii).

Fig 1 : Example from Khao Yai, central Thailand, at an approximate elevation of 1000 metres.

Fig 2 : Silt laden stream after heavy rain at Khao Yai, Thailand.

Figs 3 and 4 : Probable female in a clear stream with mixed sandy/rocky substrate at Khao Yai, Thailand.


Acknowledgments : Thanks to Ng Bee Choo for organising our visit to Khao Yai National Park.


References :

Hiroshi, T. & Matsui, M. (2002) Male-Male Combat and Head Morphology in a Fanged Frog (Rana kuhlii) from Taiwan. Journal of Herpetology, 36, 520–526.

McLeod, D. S. (2008). A new species of big-headed, fanged dicroglossine frog (Genus Limnonectes) from Thailand. Zootaxa, 1807(1), 26.