On Stenocypris (Crustacea, Ostracoda) species from Yunnan Province, southwestern China, with a description of a new species

Surveys of waterbodies in Yunnan Province have yielded six species of the non-marine ostracod genus Stenocypris Sars, 1889, two of which have been previously described (Stenocypris hirutai Smith & Kamiya, 2006 and S. orientalis Victor & Fernando, 1981). One species is described as new, Stenocypris menghaiensis sp. nov., and the other three are left in open nomenclature due to the scarcity of specimens. The newly described species is similar to S. orientalis in valve shape and morphology of most appendages, but it has reduced natatory setae on the antennae, in contrast to the long natatory setae in S. orientalis.

Reduced antennal natatory setae are a relatively uncommon feature of the genus, found in only five of the 40 previously described species, but of the six Stenocypris species recorded in this study, a total of four have reduced natatory setae. This is probably a result of the habitats targeted, as reduced natatory setae are often associated with lotic habitats, such as spring discharges and riverine environments, but it could also indicate that the genus has a relatively high colonization rate of lotic environments in southwestern China.

We highlight several morphological characters that are potentially useful for the taxonomy of the genus, including the width of the posterior calcified inner lamella, the ventral groove on the left valve, carapace surface micro-ornamentation, length of antennal natatory setae, and length ratios of setae on the sixth limb.