Circoniscus hamatus, VAN NAME, 1936

Schmidt, Christian, 2007, Revision of the Neotropical Scleropactidae (Crustacea: Oniscidea), Zoological Journal of the Linnean Society 151, pp. 1-339 : 70

CIRCONISCUS HAMATUS VAN NAME, 1936

Circoniscus hamatus Van Name, 1936 – Paulian de Félice (1944); Souza & Lemos de Castro (1991 *); Boyko (1997); Leistikow & Wägele (1999 *); Schmalfuss (2003 *).

Circoniscus gaigei (pro parte) – Lemos de Castro (1967); Schultz (1995).

Material examined

Type specimens: Five ♂, one ♀, slides with male pleopods 1 and 2 (paratypes, Guyana, Kamakusa , AMNH 6534 ) .

Description

Male 9.0 × 4.8 mm.

Coxal plate 1 with schisma, the following coxal plates simple.

Cephalothorax: linea supraantennalis somewhat distant from sockets of the second antennae. Male pereiopod 7 on frontal face not with the modifications seen in C. ornatus (although poorly preserved and partly obscured by dirt, there seem to be no such ridges, or at least these are much more shallow than in the preceeding species). The ischium has a distinct conical protrusion on the caudal face of the distal margin (not drawn).

Pleopod 1 and 2 exopodites with dorsal respiratory fields. Male pleopod 1 exopodite rounded, not with a distinct distal lobe as in Ci. ornatus . Pleopod 1 endopodite apically curved outwards, with a row of small spine-shaped setae along the dorsal spermatic furrow. This row is broken by a short recurrent portion in the subapical position. (In the paratype, the small setae of the apical part could be seen at 400× magnification.) Male pleopod 2 exopodite with lateral margin evenly concave; distal lobe distinctly curved outwards. Inner margin of exopodite 2 with pectinate scales forming a hairy furrow.

Affinities

Circoniscus hamatus is probably the sister species of C. ornatus . On the male pleopod 1 endopodite, the dorsal row of small spine-shaped setae, which is broken by a short subapical transverse or recurrent portion, can be considered as a synapomorphy of both species.

Geographical distribution

Guyana, French Guiana.

Remark

Circoniscus hamatus was cited in the synonymy of C. gaigei by Lemos de Castro (1967) and Schultz (1995). As C. gaigei auct. has proven to be C. ornatus , whereas C. gaigei Pearse, 1917 represents a different species, this synonymy cannot be maintained. Circoniscus hamatus is provisionally regarded as a distinct species, because the known characters differ from both C. gaigei and C. ornatus . The examination of more specimens from the respective type localities may determine whether the specimens described as C. hamatus belong to a distinct species, or are probably immature or abnormal specimens of C. gaigei or C. ornatus .