Nannoniscidae
Creators: name: Wilson, George D. F.
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Nannoniscidae

description: Key to the genera of the Nannoniscidae
Because the posterior somite articulation is an unreliable character but nevertheless is used in previous keys (Siebenaller & Hessler 1981; Kussakin 1999), this key uses different characters, and recognises useful features such as the form of the pleotelson. Micromesus, added to the family by Svavarsson (1984), is included. This key is also designed to be used without dissection; although the mandibular palp is used, this character can be determined on intact specimens. The composition of some genera, like Panetela (discussed above) and Austroniscus, need to be reconsidered as some species differ from the generic concepts established by Siebenaller & Hessler (1981) and may not key out properly here. For example, the narrow­bodied species A. coronatus Schiecke & Modigh­Tota, 1976, although accepted to be Austroniscus by Kaiser & Brandt (2007), probably needs to be placed elsewhere. This species may key out as Nannoniscoides.
1. Antennula with 5 articles, distal article bulbous...........................................................................................2
­ Antennula with 6 or more articles, distal article tubular or rounded............................................................3
2. Antennula article 4 distomedial margin with shelf­like process...................................................................5
­ Antennula article 4 distomedial margin unmodified, lacking projections..................................................10
3. Pereonites and pleon broadly expanded laterally (distance from midline to posterior coxae subequal or less than distance from coxae to lateral margin); pleopodal operculum (pleopods I–II) in ventral view width less than half pleotelson width ......................................................................................... Austroniscus
­ Pereonites and pleon not broadly expanded laterally (distance from midline to posterior coxae greater than distance from coxae to lateral margin); pleopodal operculum (pleopods I–II) in ventral view more than half pleotelson width.....................................................................................................................................4
4. Head anterolateral margin rounded, not projecting; mandibles prognathous, often projecting anteriorly in dorsal view; pleopod II of female with ventromedial spines or projections ........................ Thaumastosoma
­ Head anterolateral margin projecting and angular; mandibles projecting anteroventrally, not prognathous, not visible in dorsal view; pleopod II of female smooth, without ventromedial spines or projections.......... .............................................................................................................................................. Nannoniscoides
5. Body narrow—pereonal margins rounded in cross­section, tergites curving ventrally, pereonites 4–5 longer than wide; ventral surfaces never with spines...................................................................................6
­ Body moderately broad—tergites projecting laterally, especially in pereonites 5–7; pereonites 4–5 wider than long; ventral surfaces often with spines or keels..................................................................................7
6. Head with projecting rostrum; antennula tiny, not projecting anteriorly; antenna short—article 5 and flagellum altogether near length of proximal articles, flagellum strongly tapering distally; mandible palp absent ............................................................................................................................................ Exiliniscus
­ Head without projecting rostrum; antennula projecting beyond margin of head; antenna normal lengtharticle 5 and flagellum altogether distinctly longer than proximal articles, flagellum weakly tapering; mandible palp present ...................................................................................................................... Panetela
7. Pleon broad and elongate—wider than head or pereonites 5–7, distinctly longer than pereonites 5–7; pleopods near length of pleotelson ............................................................................................... Nannonisconus
­ Pleon small—less than or near width of head or pereonites 5–7, subequal or shorter than pereonites 5–7; pleopods distinctly shorter than pleotelson...................................................................................................8
8. Pereopod I robust, all podomeres distinctly wider than those of pereopod II, carpus and propodus with robust elongate ventral setae ........................................................................................................ Rapaniscus
­ Pereopod I not robust, podomeres near width to those of pereopod II, carpus and propodus with simple ventral setae..................................................................................................................................................9
9. Pereon or pleopodal surfaces with at most one ventromedial spine; pereopod I and II similar in setation and width of carpus and propodus ............................................................................................. Nannoniscus
­ Pereon or pleopodal surfaces with 2 or more ventromedial spines; pereopod II carpus and propodus broader and with more robust setae than pereopod I ................................................................. Regabellator
10. Uropod biramous, antennula article 2 distal margin without projections; pleotelson broad (length near width) and shield shaped, with distolateral spines ......................................................................... Hebefustis
­ Uropod uniramous, antennula article 2 distal margin with flat dorsal spine; pleotelson narrow (much longer than wide) and ovoid, without distolateral spines ........................................................... Micromesus
description: Published as part of Wilson, George D. F., 2008, A review of taxonomic concepts in the Nannoniscidae (Isopoda, Asellota), with a key to the genera and a description of Nannoniscus oblongus Sars, pp. 1-24 in Zootaxa 1680 on pages 12-13, DOI: 10.5281/zenodo.180391