Unenlagia was a theropod from the mid-Cretaceous, living about 90 million years ago. The first birds appeared 150 million years ago, evolving from dinosaurs long before "Unenlagia" lived. Therefore, it is not an ancestor of modern-day birds, but was an evolutionary dead-end. The most bird-like dinosaur ever discovered is the 90-million-year-old "Unenlagia comahuensis", a flightless, 4-foot tall, 7.5-foot-long carnivore.