'single claw'
Late Cretaceous, 81-68 million years ago
Dinosauria, Saurischia, Theropoda, Neotheropoda, Tetanurae, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoriformes, Maniraptora, Alvarezsauridae
Perle, Norell, Chiappe and Clark (1993)