Dinosaurs were generally huge, but a new study of the unusual alvarezsaurs show that they reduced in size about 100 million years ago when they became specialised ant-eaters. The new work is led by Zichuan Qin, a PhD student at the University of Bristol and Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. He measured body sizes of dozens of specimens and showed that they ranged in size from 10-70 kg, the size of a large turkey to a small ostrich, for most of their existence and then plummeted rapidly to chicken-sized animals at the same time as they adopted a remarkable new diet: ant-eating.