Macrophthalmus (Mareotis) Barnes, 1967

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 : 40-41

Macrophthalmus (Mareotis) Barnes, 1967

( Figs. 3C , 4A )

Large, up to 40 mm carapace breadth; ocular peduncles elongate but not projecting beyond lateral carapace margins, much longer than breadth of front; front narrow, usually constricted between bases of ocular peduncles, where its breadth is 8–15% distance between external orbital angles; ischium of external maxilliped> 1.5 times length of merus (usually 1.7–2.5 times); carapace with breadth 1.3–1.7 times length (and in one species> 1.8 times length), with large, broad-based, subrectangular anterolateral teeth, with lateral margins subparallel or arched (so that greatest carapace breadth not across external orbital angles or even second anterolateral teeth), with longitudinal and/or transverse rows of granules and/or hairs on branchial regions but without clumps of granules; central region of posterior border of epistome straight, with marked concavity or (in some populations of one species) with a central protuberance; males of one species with stridulatory apparatus as described below in Paramareotis ; fingers of male chelae usually elongate with index downflexed and with differentiated teeth on both index and dactylus or on dactylus only. Intertidal, usually in relatively soft muds.

Twelve species are included which have been divided between two subgroups on morphological grounds (the groups A and B of Komai et al., 1995):

Figures

Fig. 3. Form of the carapace and adult male chela of subgroups of the genus Macrophthalmus III: (a, b) the subgenus Macrophthalmus part 2, M. transversus (a) and Macrophthalmus dentatus (b); (c) the M. crinitus group of the subgenus Mareotis. Scale bars = 5mm.

Fig. 4. Form of the carapace and adult male chela of subgroups of the genus Macrophthalmus IV: (a) the M. japonicus group of the subgenus Mareotis (both the relatively parallel-sided and relatively rounded carapace types), and (b) subgenus Paramareotis. Scale bars = 5mm.