The world’s largest worm lizard: a new giant trogonophid (Squamata: Amphisbaenia) with extreme dental adaptations from the Eocene of Chambi, Tunisia

Abstract

We here describe Terastiodontosaurus marcelosanchezi, a new amphisbaenian genus and species from the Eocene of Chambi, Tunisia. Using micro-computed tomography (μCT), we document the peculiar anatomy of the new taxon, which is characterized by extreme dental morphology, including one massive tooth on the maxilla and dentary, flat cheek teeth, and an array of other diagnostic features that readily differentiate it from all other amphisbaenians. We also redescribe the oldest named African amphisbaenian, Todrasaurus gheerbranti, from the late Palaeocene of Morocco, using μCT. Phylogenetic analysis recovers Terastiodontosaurus and Todrasaurus as sister taxa and provides strong support for a sister-group relationship of those two large-toothed amphisbaenians with extant Trogonophis. Accordingly, Todrasaurus shows that the divergence of crown Trogonophidae occurred much earlier than currently thought. Our survey of μCT scans reveals that Terastiodontosaurus, Todrasaurus, and Trogonophis are characterized by a great enamel thickness on their teeth, a feature that is absent in other examined amphisbaenians. Size estimates show that Terastiodontosaurus was the largest known amphisbaenian ever to have lived, with an estimated skull length of >5 cm. Based on new muscle data of Trogonophis, we estimate very high bite forces for Terastiodontosaurus, which would allow it to crush a wide variety of snails.