Piatnitzkysaurus (pron.:"PEA-at-NITS-key-SORE-us") is an extinct genus of megalosauroid theropod dinosaur that lived approximately 166 to 164 million years ago during the middle part of the Jurassic Period in what is now Argentina. Piatnitzkysaurus was a moderately large, lightly built, bipedal, ground-dwelling carnivore, that could grow up to 4.3 m (14.1 ft) long.