The oldest reptile anyone had found was inside a tree. The tree had turned to stone, still standing, in a sea cliff in Nova Scotia. The skeleton was in the hollow of the trunk, and it was no longer than your hand.
So how does an animal end up inside a tree? About 315 million years ago, Nova Scotia sat near the equator. It was swamp forest. The trees were giant club mosses, about a hundred feet tall. That is a ten-story building. They had almost no wood. A trunk was a thick shell of bark around a soft core.
Then a river broke its banks. Sand poured through the forest and buried the feet of the trees where they stood. The trees died. Their soft cores rotted, and their tops broke away. What was left was a ring of bark standing in the sand. A hollow stump, open at the top.
Small animals went into those stumps. Snails. Millipedes. Amphibians shaped like salamanders. And one slim animal shaped like a lizard, about eight inches long with its tail. Some of them never came out. The next flood filled the stump with sand, and sealed them in. For a century, textbooks called the stump a pitfall trap. Newer work says some of them were probably living there, as in a den. Either way, the stump kept them.
The ground kept sinking, so the forest grew back on top and was buried again. And again. All of it turned to rock. Geologists counted fossil forests at 68 levels in those cliffs, stacked like the floors of a tower. Then the last ice sheet melted, and the sea went to work on the coast. This is the Bay of Fundy, and its tides are the highest on Earth. At these cliffs the water climbs about forty feet, twice a day. And every tide takes a little more of the cliff.
In 1852, two geologists walked that beach at low tide. Charles Lyell was one of the founders of geology. William Dawson was a local, 32 years old. They dug into a large stone trunk, and there were bones inside. But it was not a reptile. They were the bones of an amphibian, and with them was a snail, the oldest land snail ever found. Dawson kept coming back. By 1859, in another stump, he had found a different skeleton. It was small and slim, and shaped like a lizard. He named it Hylonomus. It means forest dweller.
Dawson never knew what he had. In his day, the word reptile covered amphibians too. In 1964, a scientist named Robert Carroll showed that Hylonomus was built like a reptile. Reptiles lay their eggs on land, so they never have to go back to the water. For a hundred and sixty years, the little animal in the tree was the oldest reptile anyone had found.
So is it still the oldest? No older skeleton has taken its place. But in 2025, clawed footprints were reported from Australia, about forty million years older. And that same year, a new family tree placed Hylonomus just outside the reptiles, one branch away. So the title is being argued again. And the cliff is not finished. The tide still cuts it back. Every few years, new stone trunks come out of the rock.
