Arrenurus (Micruracarus) kakadu n. sp.

(Figs. 12A–D)

Material examined. Holotype male, Plunge Pool Gunlom, Kakadu NP, Northern Territory, Australia, 13° 25.917 S 132° 24.989 E, 30 September 2005 (NTM).

Diagnosis. Cauda consisting of two lobes, genital field extending onto dorsum and there widened.

Description. Male: Idiosoma 770 long and 656 wide, anterior margin concave, idiosoma colour blue. Dorsal shield complete, 332 long and 397 wide. D1 on small humps. Petiole fork-shaped, hyaline, connected to idiosoma by a hyaline membrane (Fig. 12B). Cauda indistinctly set off from remainder of idiosoma, consisting of two large lobes, with a narrow indentation (Fig. 12A). On one of these lobes with a seta-like structure, but very likely an artefact. Area of cauda near petiole without body pores, dotted in fig. 12A. Anterior coxal plates not extending to anterior idiosoma margin. Gonopore 46 long. Genital plates widest near gonopore, narrowed laterally (Fig. 12C), extending onto dorsum and there widened. Lengths of PI-PV: 28, 68, 40, 78, 42; PII medially with four setae, one of which is inserted more dorsally (Fig. 12D). Lengths of I-leg-4- 6: 120, 114, 118. Lengths of IV-leg-4-6: 150, 134, 122. Third and fourth legs with numerous swimming setae.

Female: Unknown.

Etymology. Named after Kakadu National Park.

Remarks. The new species differs from other Australian Arrenurus -species with a hyaline fork-tailed petiole in the genital plate which extends onto the dorsum and is widened there, and the shape of the cauda.