Paleontologists Digitally Reconstruct Skull of Early Tetrapod | Paleontology

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Using cutting-edge techniques, paleontologists have produced the first complete 3D skull reconstruction of a primitive tetrapod called Whatcheeria deltae.

Digital recreation of the skull of Whatcheeria deltae. Image credit: James Rawson / Laura Porro / Elizabeth Martin-Silverstone / Emily Rayfield.

Digital recreation of the skull of Whatcheeria deltae. Image credit: James Rawson / Laura Porro / Elizabeth Martin-Silverstone / Emily Rayfield.

Whatcheeria deltae lived in what is now Iowa, the United States, some 340 million years ago (Early Carboniferous epoch).

First described in 1995, the animal was up to 2 m (6.6 feet) in length including the tail.

Whatcheeria deltae is among the earliest-branching limbed tetrapods represented by multiple near-complete specimens, making it an important taxon in understanding the vertebrate water-to-land transition, said University of Bristol researcher James Rawson and colleagues.

The fossils of Whatcheeria deltae were originally squashed flat after being buried by mud at the bottom of an ancient swamp, but the paleontologists were able to use computational methods to restore the bones to their original arrangement.

The fossils were put through a CT scanner to create exact digital copies, and software was used to separate each bone from the surrounding rock.

These digital bones were then repaired and reassembled to produce a 3D model of the skull as it would have appeared while the animal was alive.

The researchers found that Whatcheeria deltae possessed a tall and narrow skull quite unlike many other early tetrapods that were alive at the time.

Most early tetrapods had very flat heads which might hint that Whatcheeria deltae was feeding in a slightly different way to its relatives, so we decided to look at the way the skull bones were connected to investigate further, Dr. Rawson said.

By tracing the connecting edges of the skull bones, known as sutures, the scientists were able to figure out how this animal tackled its prey.

We found that the skull of Whatcheeria deltae would have made it well-adapted to delivering powerful bites using its large fangs, said University of Bristols Professor Emily Rayfield.

There are a few types of sutures that connect skull bones together and they all respond differently to various types of force, added Dr. Laura Porro from the University of Bristol and University College London.

Some are better at dealing with compression, some can handle more tension, twisting and so on.

By mapping these suture types across the skull, we can predict what forces were acting on it and what type of feeding may have caused those forces.

The authors found that the snout of Whatcheeria deltae had lots of overlapping sutures to resist twisting forces from struggling prey, while the back of the skull was more solidly connected to resist compression during biting.

Although this animal was still probably doing most of its hunting in the water, a bit like a modern crocodilian, were starting to see the sorts of adaptations that enabled later tetrapods to feed more efficiently on land, Rawson said.

The teams paper was published in the Journal of Vertebrate Paleontology.

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James R.G. Rawson et al. Osteology and digital reconstruction of the skull of the early tetrapod Whatcheeria deltae. Journal of Vertebrate Paleontology, published online July 22, 2021; doi: 10.1080/02724634.2021.1927749

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