Walcott became a leading authority on trilobites and was the first person to establish that trilobites were arthropods, the group that includes modern insects and crustaceans.
Exactly why robber crabs have grown so big is a mystery, but with so few creatures making it to these remote islands, the giant crustaceans seem to have filled a niche normally taken by medium-sized mammals.
All 7 billion human beings on Earth weigh in at a hefty 287 million tons, but just one species of krill, which is that tiny crustacean eaten by large whales, weighs a total of 500 million tons on the scale together.