Hemioniscidae Bonnier, 1900

Hosie, Andrew M., 2008, Four new species and a new record of Cryptoniscoidea (Crustacea: Isopoda: Hemioniscidae and Crinoniscidae) parasitising stalked barnacles from New Zealand, Zootaxa 1795, pp. 1-28 : 14

Family Hemioniscidae Bonnier, 1900

Composition: Hemioniscus Buchholz, 1866 ; Leponiscus Giard, 1887 .

Diagnosis: Male body tear-drop shaped with prominent cuticular striations approximately 2.5–3.0 times as long as wide. Cephalon wider than long, oral cone directed anteriorly. Eyes present or absent, when present compound. Antennule article 1 with 7–9 posterior teeth, 3 setae near anterior margin, 1 seta at base of middle tooth, 2 setae on dorsal surface. Antennule article 2 with 6 lateral setae variously distributed. Antenna arising from beneath posterior margin of antennule article 1, flagellar articles of similar length. Coxal plates with or without teeth. Pereopod 3–7 ischium with deep groove. Pereopod 3–5 propodus quadrate distally, with robust seta in notch on terminal lobe. Pereopods 6 and 7 propodus tapering distally. Pleopod rami roughly in line with each other. Endopod with internal cuticular ring present basally. Pleotelson margin entire. Anal tube absent. Uropod exopod cylindrical, approximately 0.50–0.80 as long and 0.35–0.50 as wide as flattened triangular endopod.

Mature females with at least the anterior segments as in males, posterior segments variously fused to form amorphous egg sac.

Remarks: Hemioniscids can be identified by the prominent dorsal cuticular striations, anteriorly directed buccal cone, 7–9 posterior teeth on antennule article 1, entire pleotelson margin, relative lengths of cylindrical and triangular uropodal exopod and endopod. Hemioniscids are known to parasitise thoracic and acrothoracic cirripedes.

Hemioniscidae previously contained only the genera— Hemioniscus and Leponiscus . Bocquet-Vedrine & Bocquet (1972) considered the two genera to be synonymous citing a lack of any distinguishing character to keep them separate if L. alepadis is excluded, which as discussed above should probably be transferred to the genus Crinoniscus . Leponiscus Giard, 1887 , has never had a formal definition and Leponiscus pollicipedis Giard, 1887 is a nomen nudum. The type species of Leponiscus , L. anatifae Hesse, 1867 , is figured as having nine teeth on article 1 and four on article 2 of the first antenna. Other aspects of the figures appear to be inaccurate (e.g. the first antenna is shown having a 3-articled flagellum; Hesse 1867: Pl. III, fig. 10) so unless the type material is located and redescribed, or additional specimens become available, further comparison is not possible. The genus Cryptothir Dana, 1852 whose sole species, Cryptothir minuta Dana, 1852 , is a parasite of a coral barnacle is currently regarded as incertae sedis, is potentially a member of this family, but was considered to be species inquirenda by Grygier (1993) owing to the lack of detail in the original description.