Until now, the screw-and-nut system was thought to be a human innovation. But a new study reports that it exists in nature, in the legs of the Papuan weevil.

Researchers in Germany report their discovery in the journal Science. Generally, the three joints of an insect leg have the mechanics of a hinge. In the weevil, however, the coxa-trochanteral joint, equivalent to the hip joint in humans, appears to have the mechanics of a screw and nut.

Alexander Riedel, an entomologist at the State Museum of Natural History in Karlsruhe, Germany, and one of the study’s authors, first realized this seven years ago, but thought little of it. But recently Dr. Riedel, who has studied weevils for more than 20 years and identified nearly 100 weevil species, recognized the joint’s remarkableness.

“I had thought it was ordinary,” he said. “But then I realized, this is probably the only case in the animal kingdom and among all organisms.”