Circoniscus, PEARSE, 1917

Schmidt, Christian, 2007, Revision of the Neotropical Scleropactidae (Crustacea: Oniscidea), Zoological Journal of the Linnean Society 151, pp. 1-339 : 65-66

CIRCONISCUS PEARSE, 1917

Type species: Circoniscus gaigei Pearse, 1917 (m).

Diagnosis

Endoantennal conglobation. Cephalothorax with frontal shield. Coxal plate 1 with schisma, coxal plates 2 and 3 with ventral notch or simple. Second antenna with two-jointed flagellum. Apical cone longer than flagellar article and with small lateral setae. Mandible with right one/left two penicils on the hairy lobe and one penicil between hairy lobe and pars molaris, the latter represented by a tuft of hairy setae. First maxilla lateral endite on distal margin with lateral group of four stout, simple teeth, triangular lobe, slender seta, and mesal group of six slender teeth, four or five of them cleft. Mesal endite with two penicils. Second maxilla with inner lobe slightly narrower than outer lobe and bearing a field of sensilla. Maxilliped endite covered with scales. Maxilliped palp proximal article with one large seta in mesal position; second article with distal tuft of numerous equal setae on a socket and proximal tuft of few equal setae near socket; two single setae on mesal margin and two setae on lateral margin; apical article with distal tuft of setae and few setae on lateral margin. Pereiopod 1 with antennal brush. Pereiopods of male with scale-fields of various extent. Hairy ridges on male pereiopod 7 ischium and merus are not present in all species. Dactyli with apically hirsute dactylar seta, simple ungual seta with basal seta of one-third to half the length of ungual seta, some other setae and numerous scales. Vestigial water-conducting scale-rows are present on pereiopod 7. Pleopod 1 and 2 exopodites with dorsal respiratory fields. Male pleopod 1 endopodite tip bent outwards.

The structure of coxal plate 1 is assumed to be an autapomorphy of the genus ( Souza & Lemos de Castro 1991).

Arcangeli (1927) argued that Circoniscus should be a subgenus of Synarmadillo , based on the published descriptions. In his paper, no reference to specimens is made; obviously, he did not examine any material.

Andersson (1960) regarded Circoniscus bezzii , C. hamatus and C. pallidus as synonymes of C. gaigei . Souza & Lemos de Castro (1991) found that C. bezzii is distinct from C. gaigei , cited C. hamatus as species inquirenda, and described three further species. Schultz (1995) set the three new species in synonymy of either C. gaigei or C. bezzi , keeping only these two as valid species. Souza & Lemos de Castro (1991) obviously overlooked the slender seta on the lateral endite of the first maxilla. Only in specimens described as Circoniscus gracilidens did they find it, and they

KEY TO THE SPECIES OF CIRCONISCUS

1. Coxal plates 1–3 with schisma or inner lobes. Coxal plates 6 and 7 and pleon-epimera 3–5 and uropod sympodites with distinct ridge at a short distance from the margin, on the inner face.... Circoniscus bezzii Arcangeli, 1931

1.* Coxal plates 1 or 1 and 2 with schisma or lobes. Posterior half of body without ridge along margin...........2

2. Only coxal plate 1 with a schisma at its posterior corner..............................................3

2.* Coxal plates 1 and 2 with notches on ventral face........... Circoniscus incisus Souza & Lemos de Castro, 1991

3. Transverse furrow behind frontal lamina deep and wide, reaching midlength of eyes; male pleopod 1 endopodite thick, apically truncate................................................... Circoniscus hirsutus sp. nov.

3.* Transverse furrow less developed, ending in front of the inner corner of the eyes; male pleopod 1 endopodite slender, apically acute..................................................................................5

4. Male pereiopod 7 ischium and merus with scaly lobes, adult males c. 5 mm wide. Male pleopod 1 endopodite with a row of setae interrupted by a subapical, short recurrent or perpendicular part; exopodite with a constricted distal lobe............................................................ Circoniscus ornatus ( Verhoeff, 1941)

4.* Male pereiopod 7 simple (or at least with much weaker lobes; see description of Ci. hamatus )...............5

The following are known only by the type-specimens, and not all characters could be described.

5. Male pleopod 1 endopodite with continuous row of setae.............................................................................................. Circoniscus intermedius Souza & Lemos de Castro, 1991

5.* Male pleopod 1 endopodite with a row of setae interrupted by a subapical, short recurrent or perpendicular part; exopodite distally rounded; distal lobe of male pleopod 2 exopodite outcurved; adult males c. 5 mm wide...................................................................... Circoniscus hamatus Van Name, 1936

5.** Male pleopod 1 endopodite apex unknown; adult males c. 7 mm wide.......... Circoniscus gaigei Pearse, 1917

thought that it was characteristic of that species. Actually, a slender seta in this position is present in all Scleropactidae as a plesiomorphic character that was already present in the groundpattern of Crinocheta. Modifications of male pereiopod 7 are present in C. gaigei , absent in C. gracilidens , and not described in the remaining species.

Some of the doubtful species are quoted below formally as distinct species, because they are incompletely described on the basis of poorly preserved or fragmentary material, and their few known characters differ from those of the better known species. This situation is quite unsatisfactory, but can only be improved by examination of further samples, preferably from the type localities.