Fossils of a new worm lizard species from millions of years ago discovered in Tunisia

The remains could be the missing link in the hypothesis that modern lizards evolved from worms

Zarudnyi’s worm lizard, the modern relative to the fossil found in Tunisia. Photo by Johannes Els / Breeding Centre for Endangered Arabian Wildlife, Sharjah

Fossils of a new species of giant worm lizards with one huge bottom tooth and a powerful jaw that could squash snails’ shells have been discovered in Tunisia’s Chaambi mountain.

With an estimated skull length of five centimetres the fossil, which was initially discovered in 2012 but took over a decade to analyse and process, is believed to be the largest known amphisbaenian - a group of legless lizards still in existence and known for their long bodies - to have ever lived on earth between 33.9 and 56 million years ago, scientists who made the discovery recently revealed.

Named Terastiodontosaurus marcelosanchezi, the creature possessed several extreme dental features, including a great enamel thickness on their teeth, one massive tooth on the lower jaw, and flat molars.

Dentary of Terastiodontosaurus marcelosanchezi. Photographs of left dentary ONM CBI-1-647 in labial (A) and medial (B) views. Photo: The Linnean Society of London

The Tunisian members of the International team of palaeontologists that made the discovery - Mabrouk Essid, Wassim Marzougui and Rim Temani - say the newly-extracted fossils add to the hypothesis that modern lizards evolved from worms originally

“During the Cretaceous geological period [almost 145 million years ago] Tunisia used to have multiple islands such as the Kairouan, El Kef and Kasserine [where today’s Chaambi mountains are located] Islands and from those conditions, we would have such animals,” Mr Marzougui.

Mr Marzougui said that certain geological conditions that existed on those islands, such as mud, makes it possible to reduce the oxidation of dead animals’ bones and remnants, making it possible to remain intact and find today.

Unlocking the planet’s mysteries

Premaxillae of Terastiodontosaurus marcelosanchezi. Photographs of the smaller specimens: A–D, ONM CBI-1-672 in anterior (A), right lateral (B), posterior (C), and dorsal (D) views; and E–H, ONM CBI-1-1021 in anterior (E), right anterolateral (F), posterior (G), right dorsolateral (H) views. Photo: The Linnean Society of London

The fossil finds were part of a years-long field expedition in the Chaambi mountains in Kasserine, the Tunisian group of paleontologists said. But they weren't just sitting there, waiting to be discovered; the team needed to use acid to process the calcium-rich rocks around them and reveal the treasures inside.

“This island used to have some sort of lakes and rivers flowing through it, and as animals are always connected to water we thought we would find them there,” Mr Marzougui said.

“These animals would either die in those rivers and be carried to the lakes where their remnants would stay, or get washed out by the rivers’ flows if they die elsewhere,” he said.

“This is only 1 per cent of the species that could have lived before but we don’t have any traces of.”

A, map of northern Africa, indicating the position of the late early–early middle Eocene locality of Chambi-1 (CBI-1). Also shown are the sole other few Palaeogene African localities that have yielded fossil amphisbaenians (with the exception of the record from the middle Eocene of Black Crow, Namibia). Circle for Palaeocene, square for Eocene. Map adapted from d-maps (d-maps.com). B, photograph of the CBI-1 fossil-bearing locality; arrow indicates the position of the fossiliferous limestone. C, close-up photograph of the fossiliferous limestone. Photo: The Linnean Society of London

The Tunisian researcher said that the islands that existed in Tunisia millions of years ago and the creatures that lived on them were well preserved by a rock layer that formed later on the Chaambi mountains.

“These paleontological studies help us extract animals [fossils] which enables to also determine the earth’s age and the ecological atmosphere where these creatures were able to populate,” Ms Temani said.

Ms Temani said through extraction of fossils such as the worm lizard, they are able to determine how the sea depth surrounding Tunisia has changed over millennia. It is also a helpful factor to identify how marine animals transitioned into terrestrial ones.

“Through what we see now, we are able to travel to the past,” she added.

According to geologist Mr Marzougui, the most intriguing problem for them as geologists and paleontologists is the need to discover how life has evolved on this planet and how things have branched out from each other.

“Our current study’s value stems from the fact that we were able to find an intermediate form [species] that connects the worm and lizard species,” he said.

For him and other members of his international team, the confirmation of this theory brings them happiness and especially a sense of achievement that encourages them to carry out more research and accumulate further knowledge for future generations.