The leatherback turtle, Dermochelys coriacea, which is particularly well adapted to marine life, uses a mode of terrestrial locomotion that does not involve raising the entire body; it drags itself instead, which is unique to heavy animals. The primary pattern of tetrapods, using alternate movements and a diagonal sequence of the limbs, is replaced by a specific repertory of periodic and synchronous movements of the fore- and hind-limbs. The forelimbs, which have evolved into large paddles, produce lifting and forward movements of the body as if the turtle were "walking on crutches." During terrestrial locomotion, the forelimb movement, derived from swimming, is rather similar to that used during vigorous swimming, except for a reduction of the upstroke.