Lizards have been around for at least 240 million years. The oldest known ancestor of the lizard lineage, a small reptile called Megachirella wachtleri, lived during the Middle Triassic period in what is now the Italian Alps. That makes lizards older than dinosaurs, which first appeared roughly 230 million years ago.
The Oldest Known Lizard Ancestor
For years, the lizard fossil record had a frustrating gap near its beginning. Scientists knew the lineage had to be ancient, but the physical evidence was sparse. That changed with the detailed analysis of Megachirella wachtleri, a fossil found in the Dolomites of northern Italy. Using high-resolution X-ray scanning, researchers confirmed it as the oldest known member of the squamate stem, the evolutionary branch that eventually produced all modern lizards and snakes. At roughly 240 million years old, Megachirella is 75 million years older than the previously known oldest squamate fossils.
Megachirella wasn’t what you’d picture as a modern lizard. It had a mix of primitive and more advanced features, suggesting that the traits we associate with lizards today, like flexible skulls and specialized jaw structures, were acquired gradually over tens of millions of years rather than appearing all at once.
Splitting From the Tuatara Lineage
Lizards belong to a larger group called lepidosaurs, which also includes tuataras, those unusual reptiles now found only in New Zealand. These two lineages split from each other roughly 260 million years ago, before even the earliest dinosaurs existed. While tuataras remained relatively unchanged and dwindled to a single surviving species, the lizard side of the family tree exploded into extraordinary variety.
By at least the middle of the Triassic period (around 240 to 230 million years ago), squamates had evolved and begun diversifying into the major lineages that would persist for hundreds of millions of years. However, fossil evidence from this critical window remains scarce, leaving paleontologists with an incomplete picture of exactly how early lizards looked and lived during their first tens of millions of years.
The Jurassic Expansion
The crown group of squamates, meaning the group that includes the common ancestor of all living lizards and snakes plus all its descendants, originated around 190 million years ago. But confident fossil records of these “true” modern-type lizards don’t appear until the Middle to Late Jurassic, roughly 167 to 150 million years ago.
One of the oldest relatively complete squamate skeletons comes from the Middle Jurassic of Scotland, dated to about 167 million years ago. This specimen, described in 2025, shows a mosaic of features: some resembling early lizards, others hinting at a relationship with snakes. It highlights just how experimental lizard body plans were during this period. Gecko-like vertebrae have also been tentatively identified from Middle Jurassic deposits, and by the Late Cretaceous (around 100 to 66 million years ago), recognizable gecko relatives were established in what is now Myanmar, Mongolia, and Siberia.
During the Jurassic, nearly all known lizard fossils come from northern landmasses. Only fragmentary remains have turned up from Africa and India, suggesting either that lizards were less common in southern regions or that conditions for fossilization were worse there.
How Continental Drift Shaped Their Spread
Lizards evolved when the continents were still joined in the supercontinent Pangaea, giving early species the ability to spread widely on foot. This geography explains why closely related lizard groups ended up on opposite sides of the world.
A key piece of evidence comes from southern Brazil, where paleontologists found a Late Cretaceous lizard (about 80 million years old) belonging to a group previously known only from the Old World. This discovery suggests that the ancestors of both groups had a worldwide distribution before Pangaea finished breaking apart. Once the continents separated, isolated populations evolved independently. Lizards with teeth fused to the tops of their jaws came to dominate in Africa, Asia, and Europe, while their relatives in the Americas took a different evolutionary path.
South America remained an island continent for a remarkably long time. It wasn’t until about 5 million years ago, when the land bridge to North America formed, that lizard species began moving between the two continents.
Surviving the Asteroid That Killed the Dinosaurs
The asteroid impact 66 million years ago didn’t just wipe out the dinosaurs. It devastated lizards too, far more than scientists originally thought. A detailed study of fossil sites spanning the extinction boundary found that 83% of lizard and snake species went extinct. Every large-bodied lizard and snake disappeared. The most diverse lizard group of the Late Cretaceous, a now-vanished lineage with no living descendants, was completely eliminated.
Earlier analyses had suggested lizard families sailed through the extinction relatively unscathed. That turned out to be a bookkeeping error: extinct lineages had either been lumped into modern families or excluded from analysis because they couldn’t be easily classified. When researchers looked at species-level data, the devastation became clear. Out of 30 lizard and snake species found in the final stage of the Cretaceous, only five survived into the following epoch.
The survivors shared two traits: small body size and, likely, large geographic range. Smaller lizards could shelter underground or in crevices during the extreme heat pulse from re-entering debris and the prolonged freezing of an impact winter. The survivors’ teeth averaged about half the diameter of the species that went extinct, a reliable proxy for overall body size. The odds of survival dropped steeply with every increase in size.
From Survivors to 12,000 Species
The handful of small lizard lineages that made it through the extinction event inherited a world emptied of competitors. With large predatory reptiles gone and ecological niches wide open, lizards diversified rapidly. Today, squamates comprise nearly 12,000 living species, making them one of the most species-rich groups of land vertebrates on the planet. They range from tiny geckos weighing a fraction of a gram to Komodo dragons exceeding 70 kilograms.
Along the way, lizard skulls evolved a key innovation that set them apart from their tuatara relatives: increased flexibility. Many lizard lineages lost the bony bar behind the eye socket, a structure the tuatara retains. Geckos, monitor lizards, and several other groups independently lost this bar, allowing their skulls to flex during feeding. This flexibility likely contributed to the range of diets and feeding strategies that helped lizards colonize nearly every habitat on Earth, from deserts and rainforests to oceans and the edges of the Arctic.