This 2-pound dinosaur is rewriting what scientists know about evolution

A nearly complete dinosaur skeleton discovered in Patagonia is helping scientists crack the mystery of alvarezsaurs, a bizarre group of bird-like dinosaurs. The fossil of Alnashetri cerropoliciensis reveals that these animals became tiny before developing their later specialized features, such as stubby arms and ant-eating adaptations. Weighing under two pounds, the dinosaur is one of the smallest known from South America.