Ryan Photographic - Parthenopidae - Elbow crabs
The family Parthenopidae contains around 200 species in 42 genera. Their common name of elbow crab stems from their very long pincers - so their "elbow" (for want of a better term) projects a long way past their carapace.
Most members of the family are small and are found intertidally or in shallow coastal waters. Several excellent photos and a discussion of their lifestyle can be found here.
Parthenopidid elbow crab, Kri Eco, Raja Ampat, West Papua IMG_3821