Brachyuran Crabs of Cocos Island (Isla del Coco), Costa Rica: Leucosiidae, Calappidae, and Parthenopidae, with Descriptions of Two New Species

Recent additions from Cocos Island, Costa Rica, to the collections of the Natural History Museum of Los Angeles County have increased the number of species in the brachyuran crab families Leucosiidae, Calappidae, and Parthenopidae known from the island from 4 to 10. Two of these are described: Thyrolambrus verrucibrachium, new species, and Osachila kaiserae, new species. Review of all material in the LACM collections for these species has resulted in range extensions and increases in the known maximum size for several of the species. The increase in species richness suggested by these collections may make Cocos the most speciose single island in the eastern Pacific, after the remaining crab families are studied. The zoogeographic relatedness of the oceanic islands of the eastern Pacific is supported, and the link between Cocos and the Revillagigedo Islands is strengthened.