Nature, Published online: 09 April 2025; doi:10.1038/d41586-025-01052-9A body fossil of a thorny-headed worm (Acanthocephala) has been dated to the Jurassic period, about 165 million years ago. It has characteristics of both Acanthocephala and tiny animals called Rotifera, thus casting light on the origin of the acanthocephalans and bridging the evolutionary gap between jawed rotifers and parasitic, jawless acanthocephalans.