Belongs within: Arthrotardigrada.
The Styraconyxinae are marine tardigrades with four clawed, pedunculate digits on each leg.
<==Styraconyxinae
|--Raiarctus Renaud-Mornant 1981R-M86
| `--R. colurus Renaud-Mornant 1981R-M86
|--Pleocola Cantacuzène 1951R-M86
| `--P. limnoriae Cantacuzène 1951R-M86
|--Echinursellus Iharos 1968R-M86
| `--E. longiunguis Iharos 1968R-M86
|--Styraconyx Thulin 1942R-M86
| |--S. hallasiN02
| `--S. kristenseni Renaud-Mornant 1981R-M86
| |--S. k. kristenseniR-M86
| `--S. k. neocaledoniensis Renaud-Mornant 1981R-M86
`--Angursa Pollock 1979B92
|--*A. bicuspis Pollock 1979B92
|--A. abyssalis Renaud-Mornant 1981 [=A. bicuspis abyssalis]B92
|--A. capsula Bussau 1992B92
|--A. clavifera Noda 1985 [=A. bicuspis clavifera]B92
|--A. lanceolata Renaud-Mornant 1981B92
`--A. lingua Bussau 1992B92
*Type species of generic name indicated
References
[B92] Bussau, C. 1992. New deep-sea Tardigrada (Arthrotardigrada, Halechiniscidae) from a manganese nodule area of the eastern South Pacific. Zoologica Scripta 21 (1): 79–91.
[N02] Nelson, D. R. 2002. Current status of the Tardigrada: evolution and ecology. Integrative and Comparative Biology 42 (3): 652–659.
[R-M86] Renaud-Mornant, J. 1986. Tardigrada. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 254–262. E. J. Brill/Dr W. Backhuys: Leiden.