The Forests of Yesterday

The Gilboa forest dates to 385 million years ago, and the group of cladoxylopsids that includes the Gilboa trees was widespread around the world from about 385 million to 400 million years ago.

Stein noted that these early trees played a major role in establishing Earth's first terrestrial ecosystems.

"Trees really dominate those kinds of environments they're found in. They really are the entire fabric in which an entire ecology fits in a terrestrial realm," he said.

[...]

The traits of the Gilboa trees are found in many tree types throughout history, he noted.

"[The traits] cannot all be traced back to the same common ancestor, so it's clearly a recurrent evolved form," he said.

"The reason for that is probably ecology, probably something to do with a way of being a large tree or a large plant. It's one way to do it, and it is now clearly the oldest way," he added.

From National Geographic's wesbite.

First, wow, forests 400 million years ago. Silurian Forests. wow.

Second, note for SF writers, there's something to chew on for your world building.