Around 400 million years ago, the world was warm. Animals were beginning to emerge from the oceans, and plants began to spread across the Earth. The northern Appalachian mountains were raised as the continents of Euramerica and Gondwana met. And the fish family reached a major splitting point.
One group branched off to become the lobe-finned fishes (like the famous coelacanth), which later spun off a group called the tetrapods. That’s us—we’re tetrapods, along with all other mammals, reptiles, birds, and amphibians. The other group became what we think of as stereotypical fish: the ray-finned fishes. That’s more or less every bone-filled fish you can think of: tuna, eels, goldfish (but not sharks; they’re cartilaginous, not bony).
A paper in Nature this week reports that ray-finned fishes may be a whole 40 million years younger than previously thought—and that a number of fossil species have been placed in the wrong slot on the family tree. The finding points to how crucial this period in evolutionary history is to our understanding of the evolution of modern vertebrates. And in the process, it clarifies the history of a strange fish that still lives in Africa called the bichir.