Macrophthalmus (Chaenostoma) Stimpson, 1858

Barnes, R. S. K., 2010, A Review Of The Sentinel And Allied Crabs (Crustacea: Brachyura: Macrophthalmidae), With Particular Reference To The Genus Macrophthalmus, Raffles Bulletin of Zoology 58 (1), pp. 31-49 : 37

Macrophthalmus (Chaenostoma) Stimpson, 1858

( Fig. 1A )

Small, carapace breadth <15 mm; ocular peduncles short and stout, not projecting beyond lateral carapace margins, subequal in length to breadth of front or shorter; front broad, not constricted between bases of ocular peduncles, where its breadth is 20–30% the distance between external orbital angles; ischium of external maxilliped some 1.25 times length of merus; carapace with breadth <1.3 times length, with lateral margins parallel, with broad-based subrectangular anterolateral teeth, without conspicuous aggregations of granules into rows or clumps on branchial regions; central region of posterior border of epistome straight; males without stridulatory apparatus; fingers of male chela short with index straight or slightly downflexed, and with a differentiated tooth only on dactylus. Intertidal, but unusually for Macrophthalmus , mainly associated with rocky or stony habitats.

Two species are included in Chaenostoma (= Mopsocarcinus Barnes, 1967 ): M. boscii Audouin, 1825 (type species) and M. punctulatus Miers, 1884 . This subgenus was suggested by Barnes (1967) to approximate the form of the ancestral Macrophthalmus , but the molecular sequence analysis of Kitaura, Nishida & Wada (2006) places it as a highly derived form.

Figures

Fig. 1. Form of the carapace and adult male chela of subgroups of the genus Macrophthalmus I: (a) subgenus Chaenostoma, (b) subgenus Euplax and (c) subgenus Hemiplax. Scale bars = 5mm.