Fossil discovery reveals giant worm lizard with snail-like jaws

Unlike today's predominantly subterranean worm lizards, this species may also have been a surface dweller. The fossil shows extreme dental features, including powerful jaws and a specialized tooth enamel, indicating that it fed on snails - a diet that has continued for more than 56 million years.

The worm lizards (Amphisbaenia) are aptly named, because at first glance these scaly reptiles resemble worms with heads on both ends. However, what is reminiscent of a creature from Greek mythology is actually an evolutionary trick: worm lizards can crawl both forward and backward with the tip of their blunt, rounded tail.

Among other things, they use their body shape, which is reminiscent of an earthworm, to move through narrow passages in the ground that they dig themselves.

 An international team led by Professor Dr. Georgios L. Georgalis from the Institute of Systematics and Evolution of Animals of the Polish Academy of Sciences, Krakow, together with researchers from the Senckenberg Research Institute and the Natural History Museum in Frankfurt, the Institut des Sciences de l'Evolution de Montpellier, the Musée national d'Histoire naturelle in Paris, and the National Office of Mines in Tunis, has now described a previously unknown fossil species of the worm lizard group in a new study.

"Our discovery from Tunisia, with an estimated skull length of over five centimeters, is the largest known worm lizard species," explains Georgalis. "All evidence indicates that the new species is related to the modern-day checkerboard worm lizard."

Unlike recent Amphisbaenia, which is adapted to a subterranean lifestyle, the new species Terastiodontosaurus marcellosanchezii was probably too large to have lived exclusively in burrows. The researchers therefore assume that the animal also spent a significant amount of time on the surface.

 "If the worm lizard could grow as big as a snake, the new species would be comparable to Titanoboa, which grew up to 13 meters long—in other words, significantly larger than its closest relatives. We think that the unusual body size is related to the high temperatures during this period in Earth's history," added co-author PD Dr. Christer Smith from the Senckenberg Research Institute and Natural History Museum Frankfurt.

Using micro-computed tomography, the research team documented the special anatomy of the new species, which dates back to the Eocene period. The worm lizard is characterized by an extreme dental anatomy—a large tooth in the upper jaw, with flattened molars and many other features—that distinguish it from all other amphisbaenians.

 "Visually, you might imagine the creature as a 'sandworm' from the 'Dune' science fiction novel and its film adaptation. Based on the structure of the teeth and the unusually thick enamel, we can assume that the creatures had a lot of muscle power in their jaws," Georgalis explains.

"We know that today's checkerboard worm lizards like to eat snails by breaking open their shells. We can now assume that this lineage was specialized in feeding on snails 56 million years ago and could effortlessly crack them open with their powerful jaws. This feeding strategy is therefore highly adaptable—it has defied all environmental changes and has remained with the lineage to this day," Smith added.