Paleontologists have described a new genus and species of trogonophid amphisbaenian (worm lizard) from fossilized specimens found in Tunisia.
Life reconstruction of Terastiodontosaurus marcelosanchezi ready to prey on a large snail of the family Bulimulidae. Image credit: Jaime Chirinos.
Terastiodontosaurus marcelosanchezi lived in what is now Africa during the Eocene epoch, some 47 million years ago.
The new species belongs to Trogonophidae, a small family of limbless, carnivorous, lizard-like reptiles within the clade Amphisbaenia.
“Amphisbaenians are a charismatic group of fossorial squamates, with bizarre morphological features and extreme anatomical modifications,” said lead author Dr. Georgios Georgalis from the Institute of Systematics and Evolution of Animals at the Polish Academy of Sciences and his colleagues.
“In particular, their unique skeletal anatomy has attracted and puzzled researchers since the 19th century.”
“Before the advent and broad acceptance of phylogenetic systematics, amphisbaenians were considered to be the third major group of Squamata, together with Serpentes and the paraphyletic ‘Lacertilia’.”
“Recent phylogenetic analyses, however, have placed them as the sister group of lacertid lizards, a topology that has been supported by both molecular and combined morphological and molecular evidence: a name, Lacertibaenia, was even proposed for the clade Amphisbaenia + Lacertidae.”
“Amphisbaenians have a relatively rich fossil record across the Cenozoic of Europe and North America, coupled with a few Neogene and Quaternary occurrences from South America, a few Palaeogene, Neogene, and Quaternary occurrences from Africa, a very few Neogene occurrences from the Arabian Peninsula, and a very few occurrences from the Neogene of southwestern Asia.”
“Trogonophidae are a rather distinctive group of amphisbaenians that are today distributed in northern and north-central Africa (including Socotra Island, Yemen) and the Middle East,” they added.
“Four living genera are currently recognized, i.e. Agamodon, Diplometopon, Pachycalamus, and the type genus, Trogonophis.”
The most distinctive feature of trogonophids is their acrodont dentition, a feature that, within squamates, is otherwise present solely in the iguanian group Acrodonta.”
“Trogonophids also possess other unique features among amphisbaenians, including locomotion and burrowing patterns, shoulder girdle or hemipenial morphology, chromosomes, vertebral arrangement, the absence of caudal autotomy, and a triangular body in cross-section.”
Several specimens of Terastiodontosaurus marcelosanchezi were found at a fossil-bearing locality in the Natural Park of Djebel Chambi in Tunisia.
“The Djebel Chambi National Park is situated in the Kasserine area, in the Central Western part of Tunisia,” the paleontologists said.
“The material of this study comes from a fossil-bearing site (Chambi locus 1), which consists of fluvio-lacustrine deposits situated at the base of the continental sequence of Chambi.”
“These localities have yielded a diverse assemblage of aquatic and terrestrial vertebrates, including fishes, amphibians, turtles, crocodiles, squamates, birds, and mammals, such as bats, primates, eulipotyphlans, hyaenodonts, hyracoids, an elephant shrew, a marsupial, a rodent, and a sirenian.”
Terastiodontosaurus marcelosanchezi was over 90 cm (35 inches) in length, making it the largest known amphisbaenian to ever live.
“Amongst extant amphisbaenians, Amphisbaena alba is the largest species, reaching a maximum total length of 81 cm (32 inches) and a skull length of over 3.1 cm (1.2 inches),” the researchers said.
Practically all living amphisbaenians represent burrowing animals, which appear only rarely on the surface, outside their subsurface environments.
Nevertheless, certain features in Terastiodontosaurus marcelosanchezi seem to contradict this natural history pattern and suggest instead that the ancient species was likely to be a surface dweller.
This is further supported by the extreme size of Terastiodontosaurus marcelosanchezi, which would render subsurface habits as less likely.
“Terastiodontosaurus marcelosanchezi represents a substantial contribution to the so far poorly known African fossil record of Amphisbaenia, representing only the fifth named extinct species from the continent,” the scientists concluded.
“Moreover, the new material from Chambi adds further to the extremely poor fossil record of Trogonophidae.”
The new species is described in a paper published this week in the Zoological Journal of the Linnean Society.
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Georgios L. Georgalis et al. 2024. The world’s largest worm lizard: a new giant trogonophid (Squamata: Amphisbaenia) with extreme dental adaptations from the Eocene of Chambi, Tunisia. Zoological Journal of the Linnean Society 202 (3): zlae133; doi: 10.1093/zoolinnean/zlae133