Unenlagia is the most bird-like dinosaur found so far - it even had arms that were designed so they could flap like a bird's wings.  However, this dinosaur was much too large to fly, but it clearly shows how some dinosaurs were evolving to look and act like modern birds. Some scientists think that Unenlagia is actually a young Megaraptor, as the fossils were found in the same area. It is from the same general family that also includes many of the dinosaurs that exhibited bird-like traits, including those falling into the popular raptor category. It had a very pronounced backward-pointing pubis, and it appears as though its shoulder was designed to allow for flapping movements.
   Unenlagia had a shoulder structure that allowed its short arms to move forwards, backwards, inwards (for grasping prey), and up and down (for a flapping motion). This flapping motion was not used for flying, because its wing-like arms were too short to support the heavy dinosaur. Perhaps these proto-wings were used for balancing, turning, and a bit of lift during high-speed running. Although there is no fossil evidence of feathers from Unenlagia, it may well have had them, further adding lift to each upstroke of the proto-wings. It could grasp prey with its clawed, short, wing-like forearms. This new fossil helps show how dinosaur forearms evolved into the wings of modern-day birds.
   Unenlagia shoulder and arm design provide evidence relating to the origins of flight. Paleontologists have debated about the origins of flight. Did animals first leap from trees and glide, or flap and rise from the ground? Unenlagia's bone structure supports the latter theory, in which animals start from the ground up. On the other hand (or proto-wing), Unenlagia might have evolved, like the ostrich, from an earlier flying dinosaur; after all, birds had existed for over 60 million years already when Unenlagia lived.
   Twenty fossilized bones from Unenlagia were unearthed in an ancient river bed in the Patagonia region of Argentina (southern Argentina) by Fernando Novas, of the Museum of Natural History in Buenos Aires. Novas named the fossil Unenlagia comahuensis, meaning "half bird from northwest Patagonia," in a combination of Latin and the language of the local Mapuche Indians. Novas' discovery is described in the May 22, 1997, issue of Nature.
   Were these animals basal birds? No, for they lived at a time when small, highly aerodynamic birds had been in existence for several tens of millions of years. But they probably resembled the true basal birds, which may have been present during middle Jurassic time, 80 million years before Unenlagia was alive.