When feathered dinosaurs roamed the Earth, so did giant fleas that sucked their blood.

Scientists have found the fossils of these fleas in China, and published a study of them in the journal Nature. They are about 165 million years old, making them the oldest fleas ever found.

These fleas grasped onto and crept along dinosaur feathers, said André Nel of the National Museum of Natural History in Paris, who co-authored the study. They didn't have wings, but their legs were specialized to grasp feathers. At about 0.8 inches long, they were five to 10 times bigger than fleas you typically encounter today, Nel says.

The main significance of this discovery, according to scientists, is that the fleas are not directly related to the order Diptera, true flies, which developed first, Nel said.

They are also not exactly ancestors of modern fleas, although they belong to the same lineage, Nel said.

They probably evolved alongside feathered dinosaurs, Nel said. Scientists believe other fleas evolved later to feed on mammals, and finally birds.

Modern fleas didn't appear until about 60 million years ago, Nel said.