Image: STEVE PASSOA/USDA

A recently found fossilized tick has entomologists now questioning many of their earlier assumptions about the creatures' origins. Workers from the American Museum of Natural History in New York City uncovered the fossil of Carios jerseyi in the mid-1990s when they excavated an 80-pound amber outcrop in a vacant lot in central New Jersey. The museum then turned the find over to Hans Klompen of Ohio State University.

After analysis, the fossil turned out to be much older than expected, at 90 to 94 million years old. The oldest representative of the order Parasitiformes before this one had been only 35 to 40 million years old. The new specimen's great age has cast theories on tick evolution into question¿in particular, where ticks came from initially. "The idea that ticks originated in South America has not been helped by this find," Klompen says. "The specimen is old enough that it should not have been found in New Jersey."

Another puzzle of the new fossil are two rows of about three dozen tiny hairs on its back. "It was very surprising," Klompen says. "Soft ticks normally have far fewer hairs over their entire body. But this tick is much closer to what I anticipate as the evolutionary starting point of all ticks."

Carios jerseyi shows similarities to a group of ticks that often feast on birds. This resemblance, combined with the fact that the amber contained a small feather from an unidentified bird, leads Klompen to suspect that the tick may have fed on birds and simply hitched a ride to New Jersey. If so, it would explain the seeming contradiction to the South American origin theory: "With what we know about the ancestral stomping grounds of ticks, this tick would have had to have a host to get to New Jersey," Klompen says. "And it almost had to be a host that flew."