Heterozius

Heterozius rotundifrons, or big hand crab, is a species of crab of the family Belliidae, endemic to New Zealand. The carapace width is up to 25 mm.

Behavior
When threatened, Heterozius rotundifrons has a unique antipredator behavior where it fully extends all its limbs including its chelipeds and becomes immobile. The crab keeps defensive stance for up to a few minutes.