English: The famed ‘sickle claw’ of pedal digit II in dromaeosaurids and its hypothesized uses. (A) Schematic illustration of the left pes of Deinonychus (after Ostrom, 1969b), which also illustrates the widespread inference that digit II was retracted off the ground when the claw was not in use. (B–H) Various hypotheses previously proposed for how the claw was used in life. (B) Kicking or slashing of prey. (C) Used for gripping onto the flanks of struggling prey. (D) Using body weight to drive the claws down the side of the prey’s flank. (E) Piercing or slashing specific vital areas of the prey. (F) Pinning down and immobilizing prey to be dispatched by the mouth and forelimbs. (G) Intra- or interspecific defence. (H) Digging out prey from nests or burrows. The schematics in B–H are based as closely as possible on the original descriptions (and sometimes illustrations) of the hypothesized behaviours in the literature; see main text for citations. Also note that integument (e.g., feathers) is omitted for clarity.