A tiny fossil discovered on the Devon coast in the UK has been identified as the oldest known member of the reptile group that includes lizards, snakes, and the tuatara. The new species, Agriodontosaurus helsbypetrae, lived during the Middle Triassic period, about 245 million years ago, making it 3–7 million years older than any previously known lepidosaur.
The near-complete skull and skeleton, just 10 cm long, reveal a small predator with sharp, piercing teeth suited for eating insects. Unlike modern lizards, its skull was stiff and not built for swallowing large prey. Crucially, it lacked a complete lower temporal bar, a bony arch behind the eye which later evolved into the flexible skull structure that helped make lizards and snakes so successful.
Fig: Evolution of lepidosaurs among amniotes.
The fossil belongs to the rhynchocephalian branch of lepidosaurs, which today includes only the tuatara of New Zealand. Its discovery pushes back the origin of lepidosaurs and shows that key skull features, like the open temporal bar were ancestral traits, later modified in squamates.
This finding, published in Nature, fills a major gap in understanding the early evolution of reptiles and highlights how the Triassic period was a pivotal time for the rise of modern vertebrate groups.
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Reference:
Marke, D., Whiteside, D.I., Sethapanichsakul, T. et al. The oldest known lepidosaur and origins of lepidosaur feeding adaptations. Nature (2025). https://doi.org/10.1038/s41586-025-09496-9
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