Heterodina, Schotte & Kensley, 2005

Schotte, Marilyn & Kensley, Brian, 2005, New species and records of Flabellifera from the Indian Ocean (Crustacea: Peracarida: Isopoda), Journal of Natural History 39 (16), pp. 1211-1282 : 1258-1259

Heterodina , gen. nov.

Type species. Heterodina mccaini sp. nov., by present designation.

Additional species. Cassidinidea mosaica ( Kensley and Schotte, 1987) .

Diagnosis

Male. Body dorsoventrally somewhat compressed, length more or less twice maximum width; with membrana cingulata; integument smooth or finely tuberculate; margins with fringe of setae. Cephalon embedded in pereonite 1; eyes dorsal. Epistome visible in dorsal view. Coxal extension on ventrum of pereonite 1 absent; pleonal tergite absent. Exopod of uropod very small, set into margin of endopod. Pleon with free lateral margins. Pleotelson triangular, apex extending slightly beyond uropod.

Pleopod 1 with endopod reduced, about half length and half width of exopod. Pleopod 2, appendix masculina short and broad. Exopod of pleopod 3 without suture; both rami of pleopods 4 and 5 lamellar or with very weak folds. Penes long, tapering and basally fused.

Female. Similar to male except in genitalia. Mouthparts not metamorphosed. Marsupium formed by two opposing pockets opening at sternite 4.

Remarks

This genus exhibits a unique mix of characters which may be found singly in other ‘‘subfamily’’ groups. It differs from Cassidinidea , which it most resembles at first glance, by having the cephalon set into the first pereonite instead of having expanded lateral margins; the penes, instead of being entirely fused, are basally fused; and the appendix masculina, instead of being long and acute, is short and broad. These characters were mentioned by Bruce (1994b), who therein stated the need for a new genus to accommodate C. mosaica Kensley and Schotte, 1987 , which is herein transferred to the new genus. The morphology of the cephalon of the new genus is shared with the Leptosphaeroma group of Cassidininae ( Bruce, 1994b), which possess in contrast short, unfused penes and expanded antennular peduncles. These latter two traits are also common to those species in the Cassidina group as defined by Bruce (1994b), in which however the cephalon is not set into pereonite 1. For the same reason the new genus does not fall within Bruce’s Cassidinidea group and thus remains unallied within the ‘‘subfamily’’ Cassidininae. It may indeed signify a fourth such grouping. The structure of the brood pouch, however, is identical to that of Cassidinidea , i.e. formed by two opposing pockets and different from those in Leptosphaeroma and Cassidina as described by Harrison (1984).

Distribution

Species of the genus are known at present from Belize and the Persian Gulf. Etymology

The generic name is derived from the Greek ‘‘hetero-’’ (different or other), plus the suffixdina, indicating the subfamilial affinity.