Superfamily JANIROIDEA G.O. Sars, 1897

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Superfamily JANIROIDEA G.O. Sars, 1897

Janiroidea Sars, G.O. 1897. Parts 5, 6. Idotheidae, Arcturidae, Asellidae, Ianiridae, Munnidae. pp. 81-116 in Sars, G.O. (ed.). An Account of the Crustacea of Norway with short descriptions and figures of all the species. Isopoda. Bergen : Bergen Museum Vol. 2 270 pp. [http://biodiversitylibrary.org/page/32173043] [98].

Introduction

With 26 families Janiroidea is the largest superfamily of Asellota. They are recognised by the unique arrangement of the first two pairs of pleopods. In males these pleopods together form an operculum entirely (or sometimes with lateral parts of pleopods 3) covering the more posterior pleopods. In females pleopods 1 are absent and pleopods 2 are fused forming a discoid operculum.

While some families occur mostly in shallow rocky or coral reefs, sometimes associated with algae, many families are exclusively deep-sea. Their invasion and subsequent dominance of bathyal and abyssal benthic faunas has generated considerable discussion (Wolff, 1962; Brandt et al., 2004; Raupach et al., 2004). Janiroidea appear to be the most derived group of all Asellota (Wilson, 1987, 2024).

Diagnosis

Pleon with or without free pleonites. Mandibles without antero-exterior prolongation. Male pleopods 1 and 2 forming an operculum totally or mostly covering pleopods 3–5; peduncles of male pleopods 1 elongate, coupled (sometimes fused) with each other along midline, covering interior margins of pleopods 2; rami indistinct. Female pleopods 2 fused, forming a large operculum totally covering pleopods 3–5, rarely with median terminal incision.