Researchers have found the first small finger-like bones in the fins of a fish that lived 380 million years ago, about 15 million years before the first four-footed creatures, called tetrapods, clambered onto the land. The finding upends the most recent theory of the evolution of digits:
The need to adapt to swampy marshlands and terra firma, the theory went, is what drove the gradual shift through natural selection from fish fins suitable only for swimming to weight-bearing limbs with articulated joints. The study, however, reveals that rudimentary fingers were already present inside the fins of the shallow-water Panderichthys, a transitional species that was nonetheless more fish than tetrapod [The Daily Telegraph].
The first Panderichthys fossils were found in the 1990s, but the specimens were embedded in clay and difficult to study. To get around this difficulty, researchers ran the fossil through a CT scanner at a hospital.
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