This relatively recently extinct crab was very similar in appearance to modern crabs. It had a thick hexagonal (six-sided) exoskeleton shell, known as a carapace, covering the head and thorax. The abdomen was greatly reduced and rucked or folded under the carapace. Crabs are one of the younger crustacean groups in the 'fossil record, with less time for major change between the first representatives and today's living creatures.