Nannoniscidae

• Main Author: Wilson, George D. F.
• Format: Text
• Language: unknown
• Published: Zenodo 2008
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Malacostraca; Isopoda; Nannoniscidae; Antarctic; The Antarctic; Antarc*
• Online Access: https://dx.doi.org/10.5281/zenodo.5621387; https://zenodo.org/record/5621387

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 : 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 : {"references": ["Siebenaller, J. & Hessler, R. R. (1981) The genera of the Nannoniscidae (Isopoda, Asellota). Transactions of the San Diego Society of Natural History, 19, 227 - 250.", "Kussakin, O. G. (1999) Morskye I solonovatovodnye ravnonogie rakoobrasnye (Isopoda) cholodnix I umerennix vod severnogo polushariya [Marine and brackishwater likefooted Crustacea (Isopoda) from the cold and temperate waters of the Northern Hemisphere] Suborder Asellota. Part 2. Families Joeropsididae, Nannoniscidae, Desmosomatidae, Macrostylidae). Opredeliteli po Faune SSSR [Determinants of the Fauna], Izdavaemye Zoologischeskim Institutom Rossiiskiya Akademiya Nauk. (Ed A. F. Alimov.) St. Petersburg, NAUKA. Vol. III, pp. 1 - 383.", "Svavarsson, J. (1984) Description of the male of Pseudomesus brevicornis Hansen, 1916 (Isopoda, Asellota, Desmosomatidae) and rejection of the family Pseudomesidae. Sarsia, 69, 37 - 44.", "Schiecke, U. & Modigh-Tota, M. (1976) Erstfund eines Vertreters der Nannoniscidae (Isopoda: Asellota) im Mittelmeer: Austroniscus coronatus n. sp. aus dem Golf von Neapel. Pubblicazioni della Stazione Zoologica di Napoli, 40, 105 - 133.", "Kaiser, S. & Brandt, A. (2007) Two new species of the genus Austroniscus Vanhoeffen, 1914 (Isopoda: Asellota: Nannoniscidae) from the Antarctic shelf. Zootaxa, 1394, 47 - 68."]}