Chelantermedia, Brix, 2006

Brix, Saskia, 2006, A new genus and new species of Desmosomatidae (Crustacea: Isopoda: Asellota) from the deep sea of south-eastern Australia, Memoirs of Museum Victoria 63 (2), pp. 175-205 : 175-176

Chelantermedia gen. nov.

Type and only species. Chelantermedia composita sp. nov.

Diagnosis. Body elongated, length about 5 times longer than width of pereonite 2. Lateral margins of pereonites straight, Pereonites 6, 7 and pleotelson dorsally fused. Pereopod chelate, enlarged, carpus ventrally with 1 slender seta midway and 1 slender seta proximal to claw-seta.

Etymology. The first part of the name refers to the chela of pereopod I. Chela (Latin, a claw) and intermedia (Latin, in between) reflect the intermediate set of characters between Desmosomatidae and Nannoniscidae – as it occurs for example in the chela of pereopod I.

Discussion. The new genus shows a mixture of characters of Desmosomatidae Sars, 1897 and Nannoniscidae Hansen, 1916 , two families that are poorly differentiated. The new species, C. composita , will be important in phylogenetic studies leading to better understanding of the relationships within the family Desmosomatidae . It possesses a combination of character states not compatible with any existing genus. No desmosomatid genus has pereonites 6 and 7 and the pleotelson fused as in some nannoniscid genera, for example Rapaniscus Siebenhaller and Hessler, 1981 . All nannoniscid genera including species with fused pereonites 6 and 7 ( Hebefustis Siebenhaller and Hessler, 1977 , Rapaniscus , Regabellator Siebenhaller and Hessler, 1981 , Nannoniscoides Hansen, 1916 , Nannoniscus Sars, 1870 , Saetoniscus Brandt, 2002 ) have an antennula with a bulbous distal article. The new genus does not possess such a specialisation, the flagellar articles of the antennula tapering towards the distal article. Pereopod I resembles most species of Prochelator Hessler, 1970 , Chelator Hessler, 1970 or Oecidiobranchus Hessler, 1970 . Prochelator is the only one of these three that includes species with biramous uropods but none has fused pereonites.