Mantis shrimp are carnivorous marine crustaceans of the order Stomatopoda (from Ancient Greek στόμα (stóma) 'mouth', and ποδός (podós) 'foot')
Stomatopods branched off from other members of the class Malacostraca around 340 million years ago. Mantis shrimp typically grow to around 10 cm (3.9 in) in length, while a few can reach up to 38 cm (15 in).
A mantis shrimp's carapace (the hard, thick shell that covers crustaceans and some other species) covers only the rear part of the head and the first four segments of the thorax. Varieties range in colour from shades of brown to vivid colours, with more than 450 species of mantis shrimp known.
They are among the most important predators in many shallow, tropical and subtropical marine habitats. However, despite being common, they are poorly understood, as many species spend most of their lives sheltering in burrows and holes.
Called "sea locusts" by ancient Assyrians, "prawn killers" in Australia, and now sometimes referred to as "thumb splitters", because of the animal's ability to inflict painful wounds if handled incautiously, mantis shrimp have powerful raptorial appendages that are used to attack and kill prey either by spearing, stunning, or dismembering. Some mantis shrimp species have specialised calcified 'clubs' that can strike with great power, while others have sharp forelimbs used to seize the prey (hence the term "mantis" in their common name).