Nannoniscella, George, 2001

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 : 1849-1851

Nannoniscella n. gen.

(®gure 11)

Type species. Nannoniscella biscutatus ( Siebenaller and Hessler, 1977) , 5 Nannoniscoides biscutatus Siebenaller and Hessler, 1977 .

Diagnosis. Leutzinae with body broad, sixth and seventh pereonites free, not fused. Antennula composed of six or more articles. Cephalic keels well developed or not. Pleotelson with posterolateral spines.

Remarks. Siebenaller and Hessler (1977), while presenting a generic key to the family Nannoniscidae , accommodated the genus in the dichotomous key in two branches, one comprising the genera with sixth and seventh pereonites free and the other comprising the genera with sixth and seventh pereonites fused. The reason for this situation is the fact that species of Nannoniscoides included both species with free posterior pereonites and others with fused posterior pereonites. The taxonomic treatment of the genus is corrected in this paper. These authors clearly stated that `Nannoniscoides biscutatus and N. coronarius may be readily distinguished on the basis of pereonal fusion’. Taxonomic decision should be made to designate a character above the species level. Pereonal fusion is de®nitely a morphological character at the generic level. Therefore, the eight species presently included in the genus Nannoniscoides are classi®ed into two genera (®gure 11A, B): (1) Nannoniscoides with posterior two pereonites fused, i.e. N. angulatus Hansen, 1916 (type species), N. excavatifrons ( Birstein, 1970) , N. gigas Siebenaller and Hessler, 1977 , N. latediOEusus Siebenaller and Hessler, 1977, N. laticontractus Mezhov 1986 and Nannoniscoides Sp. No. 5 Siebenaller and Hessler, 1977; and (2) Nannoniscella with posterior pereonites free, i.e. Nannoniscella biscutatus ( Siebenaller and Hessler, 1977) and N. coronarius ( Siebenaller and Hessler, 1977) .

The two species of Nannoniscella are known from the equatorial Atlantic Ocean, N. biscutatus from 3459 m in the abyssal depths (lat. 00ss03.5¾±00ss45¾S and long. 27ss48¾±29ss26¾W). N. coronarius is a bathyal species from 1493 m in the equatorial Atlantic Ocean (lat. 7ss59¾S and long. 34ss06¾W).

Among the genera belonging to the subfamily Leutzinae , Nannoniscella is related to Thaumastosoma , Austroniscus and Leutziniscus in lacking the bulbous terminal article in the antennula (®gure 12). The genera of subfamily Nannoniscinae also have genera with bulbous terminal article, i.e. Regabellator, Raponiscus and Nannoniscus and also genera without terminal bulbous article, i.e. Hebefustis and Nannoniscoides (®gure 13).