NANNONISCIDAE Hansen, 1916

George, Robert Y., 2001, Desmosomatidae and Nannoniscidae (Crustacea, Isopoda, Asellota) from bathyal and abyssal depths oOE North Carolina and their evolution, Journal of Natural History 35 (12), pp. 1831-1859 : 1843

FAMILY NANNONISCIDAE Hansen, 1916

(Nannoniscini auctoris)

Type species. Nannoniscus oblongus Sars, 1870 .

Diagnosis. Body either slender and cylindrical or broad and ¯at. Cephalon free. Pleon less commonly fused with seventh pereonite medially. Antennula often with ®ve articles, distal article usually bulbous or with additional terminal article. Antenna of male exhibiting pronounced dimorphism, having more robust and setose middle articles. Pereopods of normal length, with one major terminal claw. Coxal plates are not exceptionally ¯attened for swimming but may have plumose natatory setae. Uropods always inserted ventrally, biramous and with well-developed protopods.

Remarks. The family de®nition is written to accommodate several genera that share the common family characters. Nevertheless, there are some exceptions. For example, the south Paci®c species Nannoniscus muscarius and N. perunis ( Menzies and George, 1972) are anomalous in the family in having coxal plates on the second pereopods, projecting strongly. At the genus level, the morphologically peculiar genus Nannonisconus Schultz, 1966 has the pleon fused with the seventh pereonite medially, and broadened posteriorly unlike any other genus in the family. The bulging of the middle articles of the antenna seems common among species of genera belonging to this family but such bulging does not occur in species of the genus Austroniscus which lacks the bulbous distal articles in the antenna. This genus may belong to a diOEerent family. Siebenaller and Hessler (1977) removed the genus Thaumastosoma Hessler, 1970 from the Desmosomatidae and added it to the Nannoniscidae . They also removed the genus Sugoniscus Menzies and George, 1972 from this family because of the peculiar features associated possibly with ectoparasitic adaptation.

The diverse array of morphological con®gurations of the genera of this family may lead to division into subfamilies with more homogeneous morphology. Hessler (1970) subdivided the family Desmosomatidae into subfamilies to gain a better understanding of the systematic status. In this paper, Nannoniscidae is subdivided into three subfamilies: (1) Nannoniscinae , with ®ve genera that have sixth and seventh pereonites medially fused (®gure 6). The genera included in this subfamily are: Nanniniscus Sars, 1870, Regabellator Siebenaller and Hessler, 1981 , Raponiscus Siebenaller and Hessler, 1981, Hebefustis Siebenaller and Hessler, 1977 and Nannoniscoides Hansen, 1916 . (2) Leutzinae , with six genera characterized by sixth and seventh pereonites not fused, free (®gure 7). These genera are: Leutziniscus . gen., Nannoniscella n. gen., Thaumastosoma Hessler, 1970 , Panetela Siebenaller and Hessler, 1981 , Exiliniscus Siebenaller and Hessler, 1981 and Austroniscus VanhoOEen, 1914. (3) Conusinae , with a single genus Nannonisconus Schultz, 1966 (®gure 8) with seventh pereonite fused with pleon. (See Siebenaller and Hessler, 1981 for diagnosis of the genera belonging to the family Nannoniscidae .)