Feathered dinosaurs must have needed a good scratch. Paleontologists have discovered fossils of the oldest known fleas—insects unearthed from 165-million-year-old rocks in north-central China that ranged between five and 10 times the size of modern-day fleas, with the largest females (one shown at left) reaching lengths just over 20 millimeters and males (right) approaching 15 millimeters. These early vermin were wingless, like today's species, and their hind legs weren't yet adapted to allow the tremendous leaps for which many modern-day fleas—especially circus fleas—are famed. But the most notable aspect of these newly described fossils are the prodigious mouthparts used to pierce the hides of their hosts, the researchers report online today in Nature. Although these fleas could have fed on a variety of furred or feathered creatures, the length of their blood-siphoning weaponry, which is most prominent on females, suggests that the fleas' hosts had thick hides—a characteristic that probably applied to feathered dinosaurs but not to early mammals or birds.
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