Imagine a world where the boundaries between “fish” and “not-fish” blur, where the ancestors of birds and mammals once swam ...

These included the first fully aquatic mammals (whales) and flying mammals (bats), as well as rodents and primates. This sudden expansion of species diversity into new ways of life is known as ...

But biologists with the National Marine Fisheries Service have now discovered the oddball opah’s most distinctive feature: It is the only fish known to ... in birds and mammals, whose stable ...

as these distinguishing rocks were first studied in Devon, England. The Devonian, part of the Paleozoic era, is otherwise known as the Age of Fishes, as it spawned a remarkable variety of fish.