Four new terrestrial earthworm species from the northeast Thailand (Oligochaeta, Megascolecidae)

Earthworm specimens collected from Sakon Nakhon and Nakhon Phanom, northeast Thailand, were found to contain four new species in the family Megascolecidae, with one species in the genus Metaphire Sims & Easton, 1972, and the other three in the genus Amynthas Kinberg, 1867. These are herein named Metaphire songkhramensis Chanabun & Panha, sp. nov. in the sexthecal houlleti species group, and Amynthas sakonnakhonensis Chanabun & Panha, sp. nov., A. auriculus Chanabun & Panha, sp. nov., and A. bantanensis Chanabun & Panha, sp. nov. in the sexthecal aelianus species group. Metaphire songkhramensis Chanabun & Panha, sp. nov. occurs in dark clay soil of the oxbow lake of the river, Amynthas sakonnakhonensis Chanabun & Panha, sp. nov. occurs in wetland area, A. auriculus Chanabun & Panha, sp. nov. occurs in dark sandy loam habitats of mixed deciduous forest while the following species, A. bantanensis Chanabun & Panha, sp. nov. occurs in sandy loam habitats of paddy fields. Descriptions of the new species, including illustrations of the external and internal morphological characteristics, are provided.