Worm-like fossil is the oldest ancestor of spiders and crustaceans

A worm-like creature preserved in ancient rock has just been identified as the oldest known relative of insects, spiders and crustaceans.

The ecdysozoans are a group of invertebrate animals with a tough outer coating, or cuticle, that they moult as they grow. It is clearly a successful evolutionary strategy, because today the group contains millions of species. “Some estimates suggest that about half of all known animal species are ecdysozoans,” says Ian Hughes at Harvard University. All arthropods – including insects and spiders – belong to the group, and so do …