paleontologists have discovered fossilized remains of the world’s oldest bony fish, which swam the Devonian seas 400 million years ago.

As the earliest known bony fish, “Ligulalepis” is closely related to our own ancestors. A group of animals called osteichthians have bony skeletons and jaws, and include many modern fish and all amphibians, reptiles, birds and mammals. As Ligulalepis is near the bottom of the branch of osteichthians, it is more or less an ancestor of humans. And sheep. And salamanders. 98 percent of living vertebrates sprung from this branch of the tree of life.

Researchers at Flinder’s University in Adelaide, Australia worked with an international team of researchers to uncover and study the fossil remains of this fish. They found two fossilized skulls in Australia, neither of which were perfect—400 million years in the earth will leave remains with some wear and tear.

However, using 3D scans and micro-CT data, researchers created a digital model of the brain, based on the shape it would have taken inside the skull. They were also able to determine the shape of the skull roof and nasal and ear canals, illuminating details about how one of our earliest ancestors evolved.

According to a press release, the animal also was likely starting to develop bones in frontal fins, which would ultimately evolve into arm, wrist and finger bones. The researchers published a paper on the animal in the journal Evolutionary Biology.

The last few years have yielded several important discoveries for evolutionary biologists trying to understand details about the tree of life. Scientists recently discovered an even older ancestor of ours, resting at the base of the branch where non-bony fish (like sharks) split from bony fish (like mackerel.) Scientists have also discovered that some forms of ancient life lived without oxygen and that all animals descended from sponge-like ancestors.