Tanaocheles stenochilus Kropp, 1984

Ng, Peter K. L., 2000, The Indo-Paci ® c Pilumnidae XII. On the familial placement of Chlorodiella bidentata (Nobili, 1901) and Tanaocheles stenochilus Kropp, 1984 using adult and larval characters with the establishment of a new subfamily, Tanaochelinae (Crustacea: Decapoda: Brachyura), Journal of Natural History 34, pp. 207-245 : 212-213

Tanaocheles stenochilus Kropp, 1984

Tanaocheles bidentata Kropp, 1984: 745 ±746, ®g. 1a±f.

Material examined. Mariana Islands: Guam , Western Shoals , Apra Harbour, on L eptoseris gardineri, 27 m depth, coll. V. Tyndzik, 23 July 1981. Holotype l (6.2Ö 4.5 mm) ( USNM 210636 ); paratype m (7.3Ö 5.6 mm) ( USNM 210637 ).

Diagnosis. Anterolateral margin with two distinct spines on posterior half, anterior half unarmed (excluding external orbital tooth); merus of chelipeds with two proximal and one subdistal spines; carpus of ambulatory legs one and two with two subdistal spines, carpus of ambulatory leg three with one subdistal spine, carpus of ambulatory leg four unarmed; G1 with proximal half relatively straight, distal part relatively stout. Remarks. The present specimens agree very well with the type descriptions and ®gures provided by Kropp (1984). A further revision of his study is unnecessary. Unfortunately, only three specimens of T. stenochilus are known, which does not permit a good understanding of variation within this species. Nevertheless, there are some clear di erences between T. stenochilus and T. bidentata which for the moment, cannot be discounted by intraspeci®c variation.

In T. stenochilus , the anterolateral margin has only two spines on the posterior half, with the anterior half being unarmed (anterior part with one to two tubercles in T. bidentata ), the inner margin of the merus of the chelipeds has three spines (two spines in T. bidentata ), the carpus of ®rst and second ambulatory legs have two spines (almost always one, very rarely two in T. bidentata ), the proximal part of the G1 is almost straight and the distal part relatively stout (proximal part of the G1 gently curving outwards with the distal part relatively slender in T. bidentata ).

In addition, the colour of the two species also appears to be di erent. Kropp (1984) reported the carapace and cheliped colour of live crabs as being`reddish blond’, and the legs`white with scattered orange blotches and spots or broken orange lines’ ( Kropp, 1984: 745). In T. bidentata , the carapace, chelipeds and legs are a uniform ebony black.

Zoeal taxonomy

Methods. The ®rst stage zoeas were not stained. Appendages were dissected under a WILD M5 binocular microscope with a Ö2 supplementary lens and mounted in polyvinyl lactophenol. Cover slips were sealed with clear Sally Hansen nail varnish and the appendages were drawn using an OLYMPUS BH-2 microscope equipped with Nomarski interference contrast and attached camera lucida. Five replicates of each appendage were dissected to complete setal observations. The long plumose natatory setae of the ®rst and second maxilliped, and the antennal aesthetascs were drawn truncated. The sequence of the zoeal description (Clark et al. 1998) is based on the malacostracan somite plan and described from anterior to posterior. Setal armature on appendages is described from proximal to distal segments and in order of endopod to exopod.