Family Styloniscidae

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A common group in native New Zealand environments (North Island, South Island, subanarctic Islands). Species-level identification is difficult, and requires microscopic examination. Many species probably remain undescribed.

Most species are rather small, under 5 mm in length.

The eyes are each composed of three ocelli set in a triangle. Head rounded. Flagellum of antennae short, cone-shaped, tapers to a point; the segments of flagellum often indistinct. The body outline is interrupted between pereon and pleon. Epimeres of pleon reduced, with small posterior points. Uropods with basal part broad, rami relatively short, tapering. Pleopodal lungs absent. Colours when live vary from grey to mottled brown. Run fast when disturbed, and do not roll into a ball.

Currently, eight species are described from New Zealand (Green, 1971) in two genera:

Styloniscus - body less convex, dorsal surface smooth or granulated (in Styloniscus phormianus the head and pereon have scattered long erect setae, see S. phormianus images).

Notoniscus - body very convex and heavily sculptured, with prominent tubercles and/or longitudinal ribs. Notoniscus can be confused with heavily sculptured species of Armadillidae. The two groups can be distinguished by the number of ocelli (eye composed of three ocelli set in a triangle in Notoniscus vs. eye rounded, composed of 10-20 ocelli in Armadillidae); the flagellum of antenna (short, tapering flagellum with poorly differentiated segments in Notoniscus vs. flagellum with two segments in Armadillidae); shape of telson and uropod (pointed uropods in Notoniscus vs. broad paddle-shaped uropods in Armadillidae); the ability to roll into a ball (Notoniscus spp. do not roll into a ball, while Armadillidae do).

Hurley (1950) provides the key to the eight New Zealand species, but the key requires microscopic examination of antennal flagellum and may be difficult to use, and a number of species remain undescribed.

Species-level key to family Styloniscidae (reproduced with modifications from Hurley 1950)

1 Head with front triangularly produced .......................................................... 2
- Head rounded in front .................................................................................... 3

2. Body oblong-oval, with well marked ridges or tubercles dorsally ........... Notoniscus helmsii
- Body oval, with indistinct tubercles .............................................................. Notoniscus australis

3. Dorsal surface and antennae with distinct tubercles ............................... 4
-Dorsal surface smooth, or nearly so ............................................................. 6

4. Tubercles on body arranged irregularly .................................................... Styloniscus otakensis
- Tubercles on body arranged more or less regularly in transverse rows ... 5

5. Outer ramus of uropod about twice as long as inner .............................. Styloniscus kermadecensis
- Outer and inner rami of uropods almost equal in length ........................... Styloniscus commensalis

6. Dorsal surface with scattered longish setae. Flagellum of second antenna with no more than 4 segments.
Animal small, about 4 mm .............................................................................. Styloniscus phormianus
- Dorsal surface without scattered setae. Animal large, about 7-8 mm .... 7

7. Flagellum of second antenna with no more than five segments ............ Styloniscus thomsoni
- Flagellum of 7-10 segments ........................................................................ Styloniscus magellanicus