Once upon a time, insects had 24 legs

This ancient oddball fills a major gap in the fossil record

An illustration of an ancient insect with 24 legs

This artist's reconstruction of Chosha praecursor, a 324-million-year-old early insect with 24 legs, is helping scientists take another look at the evolutionary path insects took from water to land.

Chao Tan/Nanjing Institute of Geology and Paleontology

Insects are famous for their six-legged body plan, but that wasn’t always the rule. A 324-million-year-old fossil dug up from a shale bed in West Texas had a markedly different setup, sporting a whopping 18 extra legs along its belly — a body plan unlike that of any living insect.