Geograpsus severnsi

Specimens of G. severnsi have been recovered from several of the Hawaiian volcanic islands, including Hawaiʻi, Maui, Oʻahu and Kauaʻi. They have been found up to 2 km (1.2 mi) inland, and at altitudes of up to 950 m (3,120 ft).[1] Its range appears to have overlapped with that of the more coastal G. crinipes, a species which is widespread across the Indo-Pacific.[1]

Geograpsus severnsi was probably the largest species in the genus. Based on the size of sternites, its carapace width may have been up to 66 mm (2.6 in).[1] Its claws were 20–49 mm (0.8–1.9 in) long, and in all the specimens with both claws preserved, the right claw was larger than the left.[1] Most of the known specimens are males, but this is thought to reflect behavioral differences between the sexes, rather than an extreme sex ratio in the population.[1] This is also seen in the Ascension Island species Johngarthia lagostoma, where females are likely to die on their reproductive migration. It is therefore likely that G. severnsi had a similar ecology to other land crabs.[1] It would have been an omnivore and a predator, possibly feeding on insects, land snails and bird's eggs.[2] Outside the genus Geograpsus, there are no truly terrestrial crabs in Hawaii; the only well documented species is Chiromantes obtusifrons, which may move up to 50 m (160 ft) inland, at elevations up to 10 m (33 ft).[1]

G. severnsi is one of five species in the genus Geograpsus. Its closest relative appears to be G. grayi, a species found from the western Indian Ocean to the Line Islands and Marshall Islands.[1] G. severnsi has been known to Hawaiian zoologists since the mid-1970s, but was only formally described in 2011.[1] The specific epithet severnsi commemorates Mike Severns, the discoverer of the cave which housed most of the remains.[1]