how long were dinosaurs around

Dinosaurs were around for roughly 165–180 million years, from about 245 million years ago until their mass extinction 66 million years ago.

How long were dinosaurs around?

• Dinosaurs first appeared in the Middle Triassic, about 245 million years ago, as part of the Mesozoic Era.

• They disappeared at the end of the Cretaceous, about 66 million years ago, in the Cretaceous–Paleogene (K–Pg) extinction.

• That means dinosaurs were around for on the order of 165–180 million years, dominating land ecosystems for most of the Mesozoic Era.

Quick timeline snapshot

• Triassic beginnings: First dinosaurs evolve and start to diversify.

• Jurassic heyday: Dinosaurs become the dominant large land animals.

• Cretaceous finale: Diversity peaks, then a giant asteroid impact helps wipe out all non‑bird dinosaurs about 66 million years ago.

If the entire history of Earth were a one‑day clock, dinosaurs would rule from a little after 10 p.m. until about 11:40 p.m.—and humans would show up only in the last seconds.

Fun perspective

• A famous example: Stegosaurus (Late Jurassic, about 150 million years ago) went extinct around 66 million years before Tyrannosaurus rex ever lived in the Late Cretaceous.

• So even inside that ~165+ million‑year dinosaur span, different species were separated by tens of millions of years—far longer than our entire species has existed.

TL;DR: When people ask “how long were dinosaurs around,” the best current scientific answer is: for roughly 165–180 million years, from about 245 to 66 million years ago.

Information gathered from public forums or data available on the internet and portrayed here.