Generally, across the entire animal kingdom, joints come in two flavors: ball-in-socket or hinged. But the Trigonopertus weevil of Papua New Guinea has leg joints in an all new configuration. Their legs fit to their bodies like a screw into a nut, giving them a wide degree of motion.
The two body parts screw in together, and then allow for around 130 degrees of rotation on the back legs, and 90 degrees on the front. It doesn’t make them better walkers — weevils are rather clumsy beetles — but it can help with climbing.
By being able to move their legs further down, the Trigonopterus can get a better foothold on the leaves and twigs of the Papua New Guinea jungle, as it climbs to higher areas and better food. The screw system is also less likely to become dislocated.
Since the discovery, researchers at the museum and ANKA have studied another 15 weevils and discovered the same screwy joints on all of the tiny beetles. “Obviously, this joint exists in all weevils, of which more than 50,000 species exist worldwide,” explains Alexander Riedel from the Karlsruhe State Museum in a press release.