New insights into the life of an ancient predator, Crassigyrinus scoticus, have been revealed through digital reconstructions of its broken fossils. This species, also known as the “tadpole from hell,” roamed Carboniferous swamps over 300 million years ago and was well-equipped for hunting with its large teeth, big eyes, and various sensory adaptations. Despite scientists' attempts to understand this creature for almost a century, all known fossils were severely crushed, making reconstruction difficult. However, recent advancements in CT scanning and 3D visualization have enabled researchers to piece together the fragments, providing a glimpse into what Crassigyrinus's skull would have looked like.
The lead author of the study, Dr. Laura Porro from UCL, explains that previous reconstructions of the animal's skull were incorrect, and that it would have had a skull similar in shape to a modern crocodile. The paper, published in the Journal of Vertebrate Palaeontology, is dedicated to the late co-author Professor Jenny Clack, a renowned paleontologist who greatly influenced our understanding of early tetrapod evolution. Dr. Porro expresses her gratitude for the opportunity to work with Professor Clack on this project, and her regret that they could not continue their collaboration.
How to rebuild a flattened fossil
Crassigyrinus scoticus, a stem tetrapod, was an aquatic predator that lived in coal swamps in what is now Scotland and parts of North America over 300 million years ago. Unlike its relatives, which made the transition from water onto land, Crassigyrinus remained aquatic, either because its ancestors returned to water or never left it in the first place. Due to the fine-grained rock in which the fossils were preserved, CT scanning provides excellent contrast, but not much structural integrity. As a result, all known specimens are deformed and broken, making reconstruction challenging. The team used CT scans from four Crassigyrinus specimens, including three at the Museum, to rebuild the tetrapod's skull like a 3D jigsaw puzzle. Starting with the braincase, they assembled the palate and built upwards using overlapping areas of bone known as sutures. The resulting shallower skull shape agreed with recent re-evaluation of Crassigyrinus' body, indicating that it was a relatively flat-bodied animal with short limbs. Together, these reconstructions shed light on how Crassigyrinus lived in its aquatic environment.
What has been discovered about Crassigyrinus?
Despite its unassuming name, Crassigyrinus was a formidable predator in its time. It would have measured up to two or three meters long and behaved much like modern crocodiles, lurking beneath the water's surface and using its powerful jaws to capture prey.
The skull of Crassigyrinus contained several ridges that would have provided added strength and helped distribute the force of its bite across its numerous teeth. It also possessed specialized senses, such as large eyes for seeing in the dim coal swamps and lateral lines for detecting vibrations in the water.
There is a curious gap at the front of its snout that has puzzled scientists for some time. While it's unclear what this opening might have contained, it's possible that Crassigyrinus had an organ similar to the rostral organ found in some living fish or a Jacobson's organ, which is present in animals such as snakes and helps detect different chemicals.
Despite the mystery surrounding the gap, it's evident that Crassigyrinus had highly developed senses. To better understand the creature's capabilities, researchers are subjecting the reconstructed skull to a series of biomechanical simulations.
Source: Natural History Museum