Did All Dinosaurs Go Extinct 66 Million Years Ago?

The answer depends on how we define “extinction” and “dinosaurs.”

When we hear the word “dinosaur,” most imagine giant reptiles dominating the ancient Earth. But what if I told you that the typical notion of dinosaurs might be a bit off?

But first things first: not all prehistoric reptiles were dinosaurs. Yep, you heard that right. Sea-dwelling wonders like the ichthyosaurus, the fearsome mosasaurs, and majestic flying reptiles like Pterodactyls weren’t dinosaurs, even if they lived alongside them. This is a very common mistake in outreach literature. You should see my children looking at me every time a book or cartoon mixes these:

– No, Mom, they are wrong; Pterodactyls aren’t dinosaurs.

– I know, kiddo, and Mom’s so proud of you!

Are you mind—blown yet? This is about the fun fact, not necessarily about how I’m raising little nerdy monsters. Hold on, there’s more.

Here’s the scoop: the creatures we usually associate with dinosaurs belong to a specific group called non-avian dinosaurs. These are the ones that roamed the Earth millions of years ago, during an Era known as the Mesozoic (251.9 to 66.0 million years ago). However, a group of animals often gets overlooked in the dinosaur conversation — birds.

Birds are, in fact, descendants of dinosaurs. They share a common ancestry with Tyrannosaurus rex and Triceratops. So, when we talk about the ultimate fate of dinosaurs, whether they all went extinct, we must also consider our feathery friends fluttering around in our backyards as well as those you enjoy deep-fried in some chain restaurants. See the phylogenetic tree (a biological genealogy tree) if you want to understand these relationships better.

This revelation might prompt you to ask: “If birds are dinosaurs, does that mean dinosaurs didn’t go extinct?” Ah, there’s the rub. It all concerns our terminology and definition of “extinction” and “dinosaurs.”

Imagine a family with a unique last name. Let’s call them the Roaringtons. Now, if all members of the Roarington family except one were to perish, would we say the family has gone extinct? Well, not quite. But what if that lone survivor changed their last name to something else? Some of you may say that technically, the Roarington lineage lives on, albeit under a different name. Others may say that since the last name no longer exists, the Roaringtons are now extinct.

Similarly, when we talk about the fate of dinosaurs, we must consider whether their lineage endured through evolution. Sure, the non-avian dinosaurs that once walked the Earth may have met their demise 65 million years ago, but their legacy lives on through their avian descendants — birds. It’s like the Roaringtons changing their last name; dinosaurs evolved into a new form and we now call them something different. But their lineage persisted through time.

So, did all dinosaurs go extinct? Well, if we’re strictly talking about non-avian dinosaurs—the towering behemoths of yesteryear—then yes, they did. But if we broaden our definition to include their avian descendants, the answer becomes a bit murkier. It’s not a simple case of black or white; there are shades of evolutionary gray to consider.

In essence, the story of dinosaurs is more nuanced than we initially thought. It’s a tale of adaptation, survival, and transformation. While the thunderous footsteps of T. rex may have faded into oblivion, the soft chirps of sparrows and the graceful flights of eagles serve as a reminder of their enduring legacy. Birds have independently evolved for millions of years, from before non-avian dinosaurs went extinct.

Want to see some examples of this evolutionary path? I invite you to watch this PBS Eons episode—it’s one of my favorites!

So, the next time you spot a bird perched on a branch or soaring through the sky, take a moment to appreciate its connection to the ancient past. After all, in the grand mosaic of life, dinosaurs never truly went extinct — they evolved into something new, becoming a crucial component of the ecosystems we inhabit today.