Non-bird dinosaurs became extinct about 66 million years ago, at the end of the Cretaceous Period during the Cretaceous–Paleogene (K–Pg) mass extinction event.

Quick Scoop: When Did Dinosaurs Become Extinct?

The Short, Clear Answer

  • Non-avian (non-bird) dinosaurs disappeared roughly 66 million years ago.
  • This moment marks the boundary between the Cretaceous and Paleogene periods, often called the K–Pg boundary.

What Happened Around That Time?

Most scientists connect dinosaur extinction to a sudden global catastrophe:

  • A huge asteroid (about 6 miles / 10 km wide) struck near today’s Yucatán Peninsula in Mexico, forming the Chicxulub crater.
  • The impact likely caused massive fires, tsunamis, and threw dust and aerosols into the atmosphere, blocking sunlight.
  • This led to a rapid climate shock and collapse of food chains, wiping out all non-bird dinosaurs along with many other species.

Some research also points to intense volcanic activity (such as the Deccan Traps in India) and gradual climate shifts that may have weakened ecosystems before the impact, but the asteroid is still the leading cause in most studies.

Did All Dinosaurs Vanish?

  • Technically, not every dinosaur lineage vanished. Birds are considered living theropod dinosaurs , so a small branch survived and diversified into modern birds.
  • When people ask “when did dinosaurs become extinct,” they almost always mean the large non-bird dinosaurs like T. rex and Triceratops, which did vanish around 66 million years ago.

Fun Timing Question People Debate

In forums and discussions, you’ll sometimes see playful takes like “Was it 65 or 66 million years ago?” or jokes about the “exact day and time.”

In reality, dating that boundary to about 66 million years ago is already extremely precise on geological timescales, and that’s the figure widely used in current scientific literature.

TL;DR: Non-bird dinosaurs died out in a mass extinction about 66 million years ago , likely triggered mainly by a giant asteroid impact, right at the end of the Cretaceous Period.

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