A Review Of The Sentinel And Allied Crabs (Crustacea: Brachyura: Macrophthalmidae), With Particular Reference To The Genus Macrophthalmus Author Barnes, R. S. K. text Raffles Bulletin of Zoology 2010 2010-02-28 58 1 31 49 journal article 10.5281/zenodo.4508304 2345-7600 4508304 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.