塞氏陸方蟹

塞氏陸方蟹 Geograpsus severnsi 化石時期：
Holotype; scale bar is 10 mm
科學分類
界： 动物界 Animalia 門： 节肢动物门 Arthropoda 亞門： 甲殼亞門 Crustacea 綱： 软甲纲 Malacostraca 目： 十足目 Decapoda 下目： 短尾下目 Brachyura 科： 方蟹科 Grapsidae 屬： 陆方蟹属 Geograpsus 種： 塞氏陸方蟹 G. severnsi
二名法
Geograpsus severnsi Paulay & Starmer, 2011

塞氏陸方蟹（学名：Geograpsus severnsi）为方蟹科陆方蟹属的一個已滅絕的物種。牠們原來生活於夏威夷，在人類開始殖民當地之後很快滅絕，是歷史上首度有正式紀錄有物種滅絕。

分布

Specimens of G. severnsi have been recovered from several of the Hawaiian high 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米（3,120英尺）. Its range appears to have overlapped with that of the more coastal G. crinipes, a species which is widespread across the Indo-Pacific.

Description

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英寸）. Its claws were 20—49 mm（0.8—1.9英寸） long, and in all the specimens with both claws preserved, the right claw was larger than the left. 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. 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. It would have been an omnivore and a predator, possibly feeding on insects, land snails and bird's eggs. 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米（160英尺） inland, at elevations up to 10米（33英尺）.

Systematics

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. It has been known to Hawaiian zoologists since the mid-1970s, but was only formally described in 2011. The specific epithet severnsi commemorates Mike Severns, the discoverer of the cave which housed most of the remains.