Circulium navus ( Ng, 2012 ), 2020

Naruse, Tohru & Ng, Peter K. L., 2020, Revision of the sesarmid crab genera Labuanium Serène and Soh, 1970, Scandarma Schubart, Liu and Cuesta, 2003 and Namlacium Serène and Soh, 1970 (Crustacea: Decapoda: Brachyura: Sesarmidae), with descriptions of four new genera and two new species, Journal of Natural History (J. Nat. Hist.) 54 (7 - 8), pp. 445-532 : 460-461

Circulium navus ( Ng, 2012) , comb. nov.

Labuanium rotundatum: Ng and Liu 2003, p. 614 (part), fig. 8A–D; Paulay et al. 2003, p. 508; Cuesta et al. 2006, p. 155, fig. 4.

Labuanium navus Ng, 2012, p. 274 , figs 8–11 [type locality: Guam].

Material examined

Holotype. ZRC 2002.454a , male, 42.9 × 39.7 mm, on trees, in forest, Faifai Beach , near Gun Beach, Tumon Bay , Guam, coll. H.-C. Liu and P.K.L. Ng, 28 July–1 August 2001.

Paratypes. ZRC 2002.454 b, 6 males, 16.4 × 15.9 mm, 31.6 × 30.8 mm, 34.4 × 32.1 mm, 36.8 × 35.6 mm, 39.3 × 39.2 mm, 43.7 × 41.2 mm, 3 females, 15.1 × 14.8 mm, 28.1 × 27.3 mm, 42.5 × 39.7 mm, same data as holotype; ZRC 2002.457 , 2 males, 22.2 × 21.1 mm, 22.5 × 21.2 mm, Ritidian Point , northern Guam, coll. H.-C. Liu and P.K.L. Ng, 31 August 2001; ZRC 2002.456 , 2 males, 27.9 × 17.0 mm, 19.1 × 18.6 mm, 1 female, 11.9 × 11.6 mm, Haputo Beach forest , Guam, coll. P.K.L. Ng, 3 August 2001; ZRC 2002.455 , 1 post-ovigerous female, 31.6 × 30.4 mm, Haputo Beach forest , Guam, coll. P.K.L. Ng, 3 August 2001 (first zoeae hatched 4 August 2001) .

Diagnosis

Two pairs of postfrontal lobes present, lateral lobes exceeding mesial lobes anteriorly, anterior edge of lobes far from frontal margin in dorsal view. Epistome posterior margin with 3 low lobes, lateral lobes terminally directed anteroventrally, median lobe terminally directed anteriorly. Chela outer surface sparsely covered with large granules; upper surface with 1 complete longitudinally traversing row of small granules. G1 relatively stout, relatively long, straight proximally, distally bent about 80° against main axis; distal beak-like and corneous process truncated, narrow. Sternal vulval cover covering almost entire vulva, except for mesial hole, sternal vulval cover produced anteroventrally as trigonal pyramid projection.

Colouration

In life, generally greyish-white to grey, sometimes with pale yellow patches; eyes greyish; chelae uniformly white to greyish-white ( Ng 2012).

Distribution

Known only from Guam [type locality], Marianas.

Ecological note

Circulium navus has been observed climbing coconut trees and Pandanus vines 20–30 m from the sea, and in a few instances, near-vertical rocks at the base of large trees ( Ng and Liu 2003, as L. rotundatum ).