This article was originally featured on The Conversation. After four years of digging for fossils in a churchyard in York, Pennsylvania, amateur paleontologist Chris Haefner made an intriguing find.

Sponges may be ancient, but their timeline has been murky. New research suggests the earliest sponges were soft and skeleton-free, explaining why their fossils don’t appear until much later. By ...

When paleontologists picture the earliest animals, they tend to imagine something with at least a rudimentary skeleton: a lattice of glassy needles, perhaps, or a mesh of calcium carbonate. But a ...