New Worm Fossil Fills in History of Insect Evolution

A new study led by our Earth Sciences department has uncovered an incredibly rare and detailed fossil, named 'Youti yuanshi', that gives a peek inside one of the earliest ancestors of modern insects, spiders, crabs and centipedes.

The fossil preserves the entire internal anatomy of a tiny larva in exceptional quality that represents one of the earliest arthropod ancestors with legs and a complex brain.

Sophisticated biology

This fossil belongs to a group called the euarthropods, which includes modern insects, spiders and crabs.

Despite being no bigger than a poppy seed, the 3D fossil reveals the larva possessed an advanced brain, digestive system, circulatory system and clusters of nerves extending into primitive legs and sensory appendages.

Evolutionary clues

The fossil helps bridge a key transitional gap in arthropod evolution between simple worm-like ancestors and the successful modern arthropod body plan.

In particular, the fossil's brain anatomy reveals pivotal steps in how the arthropod head and its appendages like antennae, jaws and eyes became segmented and specialised over time from ancestral brain regions.

The researchers highlight that the fossil fills an important gap in our understanding of how the arthropod body plan originated and became so successful during the Cambrian Explosion of life.

This remarkable specimen is housed at Yunnan University in China, where it was originally discovered.

Reference: Smith MR, Long EJ, Dhungana A, Dobson KJ, Yang J, Zhang X. Organ systems of a Cambrian euarthropod larva. Nature. 2024. doi: 10.1038/s41586-024-07756-8

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