Overview

• Researchers report in Nature that Agriodontosaurus helsbypetrae is the oldest known lepidosaur, dated to about 242 million years ago.
• The holotype, recovered in 2015 from the Helsby Sandstone Formation in Devon, preserves a palm‑sized skeleton with a skull roughly 1.5 cm long.
• High‑resolution scans reveal no palatal teeth and no cranial hinging but an open lower temporal bar, overturning predictions for the ancestral skull configuration.
• Large triangular teeth suggest an insect‑eating ecology comparable to the shearing bite of today’s tuatara.
• Synchrotron CT at the European Synchrotron Radiation Facility and Diamond Light Source resolved key features and extends the lepidosaur fossil record by an estimated 3–7 million years beyond Wirtembergia.