With a Bite: World’s Largest Worm Lizard Fossil Discovered
The approximately 50-million-year-old animal from Tunisia could crack snail shells with its powerful jaws
An international team of researchers has discovered a new fossil worm lizard species in Tunisia. Terastiodontosaurus marcelosanchezi is the largest known species of the Amphisbaenia group, with a skull length of over five centimeters. Unlike today’s predominantly subterranean worm lizards, this species may also have been a surface dweller. The fossil shows extreme dental features, including strong jaws and a specialized tooth enamel, which indicate that it fed on snails – a diet that has persisted for over 56 million years.
The worm lizards (Amphisbaenia) are aptly named, since at first glance these scaly reptiles resemble a worm with a head at both ends. However, what recalls a creature from Greek mythology is actually an evolutionary trick: worm lizards can crawl both forwards and backwards with their blunt, rounded tail ends. Among other things, they use their body shape, which is reminiscent of an earthworm, to wriggle through narrow passages in the ground that they dig themselves.
An international team led by Prof. Dr. Georgios L. Georgalis from the Institute of Systematics and Evolution of Animals at the Polish Academy of Sciences, Krakow, with researchers from the Senckenberg Research Institute and Natural History Museum in Frankfurt, the Institut des Sciences de l’Évolution de Montpellier, the Muséum national d’Histoire naturelle in Paris, and the National Office of Mines in Tunis, has now described a previously unknown fossil species from the group of worm lizards in a new study. “Our discovery from Tunisia, with an estimated skull length exceeding 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 the recent Amphisbaenia, which are adapted to a subterranean lifestyle, the new species Terastiodontosaurus marcelosanchezi was probably too large to live exclusively in burrows. The researchers therefore assume that the animal also spent a significant amount of time on the surface. Co-author PD Dr. Krister Smith from the Senckenberg Research Institute and Natural History Museum Frankfurt adds, “If worm lizards could grow as large as snakes, then the new species would be comparable to the Titanoboa, which is 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 higher temperatures in this period of the Earth’s history.”
Using micro-computed tomography, the research team documented the particular anatomy of the new species, which dates back to the Eocene. The worm lizard is characterized by an extreme dental morphology – including a massive tooth in the upper jaw, flat molars, and a number of other features – which distinguishes it from all other Amphisbaenia. “Visually, you can imagine the animal as a ‘sandworm’ from the ‘Dune’ science fiction novels and their movie adaptation. Based on the tooth structure and the unusually thick enamel, we can deduce that the animals had enormous muscle strength in their jaws,” explains Georgalis. “We know that today’s checkerboard worm lizards like to eat snails by breaking open their shells. We can now assume that this lineage specialized in feeding on snails over 56 million years ago and could crack them open effortlessly with their powerful jaws. This feeding strategy is therefore extremely consistent – it has defied all environmental changes and accompanies the lineage to this day,” adds Smith in summary.
