Haplocheirus – Ancient Alvarezsaurid from China
The alvarezsaurids, a bizarre and little known group of swift, cursorial (running) dinosaurs have puzzled scientists since fossils of these unusual creatures came to light in the 1990s. Are they birds, or are they dinosaurs? These animals show features of each, for example, bird-like features include a deep keel in the chest and specialised forelimbs, fused ankles and a narrow skull. These animals were presumably covered in downy feathers and with their long beaks and long legs they would have resembled storks. However, they possessed a long tail, presumably to balance them as they ran and a bizarre, huge, single claw on the end of each hand.
Originally, known from Cretaceous strata from South America, it was thought these animals were an off-shoot of the Aves (birds). They could not fly but seem to have evolved to be fast running insectivores, perhaps using their short, but strong arms and powerful claw to break into termite nests.
Whether they were birds or members of the Dinosauria is debated, however, the discovery of the fossils of a alvarezsaurid from the Middle Jurassic has swung the debate in favour of declaring alvarezsaurids as true dinosaurs.
A dinosaur fossil discovered in north-western China and reported upon in the scientific journal “Science” has provided fresh evidence that although alvarezsaurs resembled birds, they must have evolved separately – helping confirm that modern birds are indeed living dinosaurs.