Family- Microhylidae (Narrow-mouth Frogs)

630 species in 59 genera are known from the world and they are categorized in to eleven subfamilies (Asterophrynae, Brevicepitinae, Cophylinae, Ceratobatrachinae, Dyscophinae, Gastrophryninae, Geniyophryninae, Melanobatrachidae, Microhylinae, Phrynomerininae, Scaphiophryninae). Microhylids are distributed throughout the world in warm temperate and tropical regions.  They are usually small frogs and grows up to a maximum of 100mm. They have several odd shapes ranging from  squat and small headed globular  to toad-like  and to arboreal frogs with expanded digits. Their pupils are horizontal or round. Reproduction can be direct and indirect and amplexus is axillary. Their tadpoles lack keratinous beaks or denticles.
Microhylidae in Sri Lanka
All the species of Microhylidae in Sri Lanka belong to the subfamily Microhylinae. Ten species are known from Sri Lanka. They were formally placed in  four genera (Kaloula, Microhyla, Ramanella, Uperodon). However, recent  molecular phylogenetic analysis (Peloso et al., 2015) indicate that the the Sri Lankan microhylids be placed in two genera (Microhyla, Uperedon). The members of the genera Kaloula and Ramanella are now placed in the genus Uperodon. Five species are endemic to Sri Lanka. All the species of Microhylids in Sri Lanka show indirect development and their free living tadpoles lack keratinous mouth parts.   
Genus- Microhyla Tschudi, 1838
Four species are known from Sri Lanka. Three are endemic to Sri Lanka. They are small frogs that grows upto a maximum of 35mm from snout to vent. Their tadpoles are filter feeders and feed on dissolved particulate matter dispersed in the water column. M. karunarathei is an endemic and a rare species of frog restricted in distribution in the vicinity of Rakwana hills in Sri Lanka. M. zeyalnica is an endemic  montane species distributed in the elevations above 1500m above m.s.l. M. ornata and M. mihintalei (formally M. rubra) are common species distributed in the lowlands up to an elevation of 600m above m.s.l.

Species of Microhyla in Sri Lanka
Microhyla karunaratnei Fernando and Siriwardhane, 1996E
Microhyla ornata (Dumeril and Bibron, 1841)
Microhyla mihintalei Wijayathilaka, Garg, Senevirathne, Karunarathna, Biju and Meegaskumbura, 2016E
Microhyla zeylanica Parker and Osman-Hill, 1949E

Genus- Uperodon Dumeril and Bibron, 1841
Five species are known from this genus. Three are endemic to Sri Lanka. They have a globular shape bodies with a narrow head region.  These frogs possess triangular shaped sticky finger tips that aids them in climbing (except Uperodon systoma). They are highly capable of climbing and many have been observed climbing trees and walls (except Uperodon systoma)Uperodon systoma is also seen in India, Pakistan and Nepal. It has a smooth moist skin and the body resembles a water filled balloon. This appearance has earned U. systoma the name "Marbled Balloon Frog'. This burrowing species of Microhylid frog is distributed in the lowland dry and intermediate zones of Sri Lanka. Yet a common species but rarely seen due to its' burrowing and nocturnal habits. Uperodon systoma grows up to a snout to vent length of 60mm. They can be seen more often during the rainy season in the dry zone. It is known to feed on termites. Uperodon taprobanicus (formally Kaluola taprobanica) is a common species mainly seen in the lowlands of Sri Lanka but occasionally seen in the hills up to an elevation of 500m a.s.l.  When disturbed or handled they inflate their body and also release a sticky substance from the cloaca. Uperodon taprobanicus grow to a maximum snout to vent length of 45 mm. They have triangular shaped finger tips.
Uperodon nagaoi, U. obscurus, U. palmatus and U. variegatus have flat bodies with narrow head region. They are small frogs that grow to a maximum snout to vent length of 35 mm.They are capable of climbing trees and vertical walls and bear triangular shaped finger tips. Uperodon nagaoi (formally Ramanella nagaoi)  and U. obscurus (formally Ramanella obscuraare known to lay eggs in water collected in tree holes. Uperodon obscurus is known to feed on ants and termites in captivity. Uperodon nagaoi is restricted to the lowland rainforests of the southern province of Sri Lanka while U. obscurus is distributed throughout the wet zone of Sri Lanka up to an elevation of 1000m above m.s.l.  Uperodon variegatus (formally Ramanella variegatais found in the lowlands of Sri Lanka up to an elevation of 500m above m.s.l. Uperodon palmatus is a montane species restricted to the regions above 1300m above m.s.l.     

Species of Uperodon in Sri Lanka

Uperodon nagaoi Manamendra-Arachchi and Pethiyagoda, 2001E
Uperodon obscurus (Gunther, 1864)E
Uperodon palmatus (Parker, 1934)E
Uperodon systoma  (Schneider, 1799)
Uperodon taprobanicus (Parker, 11934)
Uperodon variegatus  (Stoliczka, 1872)

Abreviations in superscript
E- Endemic species, Ex- Extinct species, Cr- Critically Endangered species, En- Endangered species

Manamendra-Arachchi, K. & Pethiyagoda, R. (2001) Ramanella nagaoi, a new tree hole frog (Microhylidae) from Southern Sri Lanka. Journal of South Asian Natural History, 5: 121–133.
Meegaskumbura, M. (2001) Ecology of Ramanella obscura (Anura: Microhylidae) in a home-garden habitat and a mid-country forest (Gannoruwa). Lyriocephalus, 4: 36–39.
Morgan-Davies, A.M. (1958) Notes on the eggs, tadpoles, metamorphosis and ecology of a Ceylonese narrow-mouthed frog Ramanella obscura (Gunther). Journal of Bombay Natural History Society. 55: 307–312.
Peloso, P.L.V.; Frost, D.R.; Richards, S. J.; Rodrigues, M.T.; Donnellan, S.; Matsui, M.; Raxworthy, C. J.; Biju, S. D.; Lemmon, E. M.; Lemmon, A. R. & Wheeler, W. C. (2015) The impact of anchored phylogenomics and taxon sampling on phylogenetic inference in Narrow-mouthed frogs (Anura, Microhylidae). Cladistics, 32: 113-140.