3D Reconstruction of a Fossil Skull Reveals the Transition from Water to Land

A new fossil may shed some light on animals' transition from water to land. Scientists have created the first ever 3D reconstruction of a skull of a 360-million-year-old near-ancestor of land vertebrates to learn a bit more about these animals.

The reconstruction wasn't easy. The scientists applied high-resolution X-ray computed tomography (CT) scanning to several specimens of Acanthostega gunnari. This was one of the four-footed vertebrates known as "tetrapods," which invaded the land during one of the great evolution transitions about 380 to 360 million years ago. Tetrapods actually evolved from lobe-finned fishes.

Using advanced softward, the researchers digitally prepared a number of these specimens from East Greenland. They stripped away layers of rock to reveal the underlying bones. This allowed them to create a detailed reconstruction of the animal.

"Because early tetrapods skulls are often 'pancaked' during the fossilization process, these animals are usually reconstructed having very flat heads," said Laura Porro, the lead author of the new study, in a news release. "Our new reconstruction suggests the skull of Acanthostega was taller and somewhat narrower than previously interpreted, more similar to the skull of a modern crocodile."

After analyzing the reconstruction, the researchers believe that the animal may have fed by initially seizing its prey at the front of its jaws, using its large front teeth and hook-shaped lower jaw. Not only that, but the models reveal that this creature may have been more crocodile-like than scientists initially suspected.

"These new analyses provide fresh clues about the evolution of the jaws and feeding system as the earliest animals with limbs and digits began to conquer the land," said Emily Rayfield, co-author of the new study.

The findings are published in the journal PLOS One.

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