Onychocamptus Daday, 1903 from Thailand, with descriptions of two new species and two new records (Crustacea, Copepoda, Harpacticoida, Laophontidae)

Abstract. In this paper, two new species of Onychocamptus Daday, 1903 are described from Thailand: Onychocamptussatunensissp. n. and Onychocamptustratensissp. n. The following features mainly distinguish O.satunensissp. n. from known species: internal sausage-like and internal rounded structures on cephalothorax and one outer seta on the male P5 exopod that is as long as the supporting segment. In contrast, the cephalothorax of O.tratensissp. n. is smooth but has rounded integumental window-like structures, and the outer seta on the male P5 exopod is two times as long as the supporting segment. Onychocamptusanomalus shows the highest similarity with the two new species, but in contrast to both Thai species, it has only one seta on the exopod of the antenna. In addition, in the present study, two additional species, O.bengalensis and O.vitiospinulosa, are newly recorded in Thailand. Thus, the number of Onychocamptus species recorded in Thailand increases to five species. A key to all known species of this genus in the world is also proposed.