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Volume 614 Issue 7946, 2 February 2023

Funky worm

The evolutionary origin of the limbless, worm-like amphibians known as caecilians is not well understood. In this week’s issue, Ben Kligman and his colleagues present fossils of the oldest-known caecilian, dating to 220 million years ago, which could help resolve the problem. The researchers identified the fossilized remains of some 76 caecilians in the Upper Triassic Chinle Formation of Petrified Forest National Park in Arizona. Named Funcusvermis gilmorei, the newly discovered species shows features found in the common ancestor of living caecilians as well as some found in an extinct group of four-legged amphibians called the dissorophoid temnospondyls. But F. gilmorei also lacks some features present in modern caecilians, which suggests it bridges the gap between modern caecilians and extinct tetrapods. An artist’s impression of F. gilmorei is shown in the foreground of the cover, together with the archosaur Acaenasuchus geoffreyi.

Cover image: Andrey Atuchin

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