Guiyu oneiros is a monumental fossil discovery — the earliest confirmed bony fish, pushing back the origin of vertebrates with ossified skeletons. It represents a key step between primitive jawless fish and the rise of modern bony fish, amphibians, and ultimately tetrapods like us.

Despite its age, Guiyu already showed a complex mix of features: heavy scales, fins with internal bones, and hints of a jaw structure. These traits place it at the root of both ray-finned fish (like trout) and lobe-finned fish (like coelacanths and lungfish). It’s a true evolutionary bridge, showing how vertebrate life was already experimenting with bones and jaws during the Silurian seas.

Its name — Guiyu oneiros, or dream ghost fish — captures the mystery of its deep-time origins and spectral reappearance in stone.