Reconstructed 330-Million-Year-Old Fossils of the 'Tadpole From Hell' Reveal a Shape Similar to a Crocodile

Scientists have used digital technology to reconstruct the fossils of the prehistoric species Crassigyrinus scoticus, which lived over 330 million years ago. The reconstructed skull revealed that the shape was similar to a modern crocodile rather than what was previously thought.

The research, titled "Computed tomography and three-dimensional reconstruction of the skull of the stem tetrapod Crassigyrinus scoticus Watson, 1929" published in the Journal of Vertebrate Paleontology, provided insights into the predator's behavior, suggesting that it hunted like modern crocodiles in coal swamps.

Reconstructing the Flattened Fossils of the 'Tadpole From Hell'

Study lead author Dr. Laura Porro of University College London (UCL) explains that the animals were preserved in fine-grained rock which makes for great contrast when using CT scanning, SciTech Daily reported. However, this rock does not provide much structural integrity, and when more material piled up on top of the fossils, it squashed them down.

Hence, all known specimens are broken and deformed, with shattered bones flattened and laid on top of each other resulting in various reconstructions. The scientists took CT scans from four Crassigyrinus specimens, including three at the Museum, which possessed all the bones needed to begin reassembling the tetrapod's cranium.

Laura started by identifying all the fossils, beginning with the remains of the braincase which would form the core of the skull. This gave her a base to work from, upbuilding the palate and using overlapping areas of bone, known as sutures, which hinted at how the skull bones fit together. They could confidently recreate the specimen since the bones were fractured rather than curved.

The final skull shape matched a recent re-evaluation of the rest of Crassigyrinus' flat body with very short limbs. By combining these reconstructions, Laura and her team can reveal more about how Crassigyrinus may have lived.

The new research reveals that the previously-reconstructed "tall skull," similar to a Moray eel, was incorrect and that Crassigyrinus had a skull shape more similar to a modern crocodile, with powerful jaws and teeth. More so, they had large eyes, sharp teeth, and sensory adaptations, making them an efficient hunter. The species has been nicknamed the "tadpole from hell."

More About the Crassigyrinus scoticus

According to Palaeos, Crassigyrinus scoticus is an unusual aquatic stem-tetrapod from the Late Mississippian and Early Pennsylvanian of Scotland. It is known from three skulls, one of which is articulated with a rather complete skeleton, and two fragmentary lower jaws.

Its small forelimbs and rudimentary traits, such as palatal structure, have sparked debate regarding its taxonomic position. The species' taxonomic position has been debated, with some regarding it as related to "anthracosaurs" and others clustering it with Whatcheeria and the embolomeres.

The holotype skull shows a more or less undistorted and complete side view, with a short pre-orbital region, quadrangular orbit, and extended suspensorial region. The skull associated with a postcranial skeleton is similar in structure to those of embolomeres, with unsutured junctions to the cheeks, but has a primitive bone pattern with supra-temporal/post-parietal contact.

The third skull demonstrates a bizarre fenestra between the premaxillae and large holes in the dorsal surface of the dentary to house the massive palatal teeth when the jaws are closed, as well as an extremely specialized, massive palatal dentition.