The charismatic Gecarcinus ruricola (Linnaeus, 1758), type species of Gecarcinus Leach, 1814, with a neotype designation and genetic data, and new generic assignment, Hartnollius n. gen., for the three remaining species of the genus

Detailed adult morphologies of the largest living brachyuran crabs have been surprisingly neglected. This is exemplified by the type genus of the family Gecarcinidae H. Milne Edwards, 1837, Gecarcinus Leach, 1814, and by its type species, the charismatic land crab G. ruricola (Linnaeus, 1758), remarkable for its considerable size, its ecological, economic and cultural importance throughout the Caribbean region. Gecarcinus currently includes three other terrestrial species: G. lateralis Fréminville in Guérin, 1832, distributed on the American continent and in the Caribbean Islands; G. quadratus Saussure, 1853 and G. nobilii Perger & Wall, 2014 only on the American continent. In the context of an ongoing revision of the Gecarcinidae by the first two authors, Gecarcinus revealed not monophyletic, which is supported by morphological and molecular data. Gecarcinus new status is redefined to include only G. ruricola; the three remaining species are transferred to a new genus, Hartnollius n. gen., with the following combinations: Hartnollius lateralis (Fréminville in Guérin, 1832) n. comb., H. quadratus (Saussure, 1853) n. comb. and H. nobilii (Perger & Wall, 2014) n. comb. We designate here a neotype for Cancer ruricola Linnaeus, 1758. Molecular data highly support that morphological differences observed through G. ruricola distribution (position of merus mxp3 in relation to frontal margin, position of extremity of sterno-pleonal cavity in relation to thoracic sternal suture 2/3) are due to intraspecific variability. Previous references to G. ruricola in Florida and Nicaragua are found to be erroneous, G. ruricola proving to be a specifically insular species. The case of Gecarcinus depressus Saussure, 1857, described from Haiti, is documented.