ananyo writes "Primitive fleas were built to sup on dinosaur blood in the Jurassic period, more than 150 million years ago. The potential host–parasite relationship has been uncovered thanks to a set of beautifully preserved fossils found in China. Today, the varied group of parasitic insects known as fleas frequently infests mammals and birds. But little is known about their origins. Researchers have now extended the history of the parasites by at least 60 million years. Whereas modern fleas range from 1 to 10 millimeters in length, the Jurassic and Cretaceous species were between 8 and 21 millimeters. The Jurassic and Cretaceous fleas also lacked the spring-legged, jumping specializations of modern species, and their siphoning mouthparts were armored structures studded with saw-like projections, unlike the smooth jaws of modern fleas."