What was the very first dinosaur?
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From the brains behind Brains On, this is Moment of Um. Moment of Um comes to you from APM Studios. I'm Ian Rankin. I get mistaken for award-winning Scottish mystery writer Ian Rankin a lot.

Unfortunately for all those autograph seekers, I'm Ian Ranking, and I love ranking stuff. You give me a list of things, and I'll put them in order. Do you need to know the best kind of potato-based side dish? I gotcha. In order of deliciousness, it's tater tots first, then shoestring fries, then breakfast taters, then scalloped, and then mashed potatoes.

Or what about ranking foods from mild to spicy? Well, if you prefer to walk on the mild side, nothing beats a lovely unseasoned bowl of oatmeal. And on the spicy end, I would say sriracha covered a ghost peppers. Not doing that again.

Now, speaking of spicy, I've got a spicy little problem on my hands. I've recently come up against a comparison conundrum. Ranking dinosaurs from oldest to most recent. See, my pal Trey was wondering, what was the very first dinosaur? And I'm stumped. Let's talk to an expert to see what the deal is with dinos.

- You know, we don't really decide that like this one species is the first dinosaur. My name is Callie Moore. I manage the fossil collection at the University of Montana in Missoula.

What we do is we compare what we think we have as a dinosaur with what we know is a dinosaur. And different characteristics of the body, let's say maybe a longer femur bone or a weird angle on a backbone.

And we line them up like, okay, this is a dinosaur characteristic and this is not a dinosaur characteristic. And then you compare them, which list is bigger. But all of evolution is a gray scale. It's usually just comes down to characteristics. And people argue about this constantly. This is not set in stone by any means. So that was a very long winded way of saying that we're not totally sure what the very first dinosaur was. We can go back probably

probably sometime into the Triassic, maybe upwards of 250 million years ago. And we know there was a very close dinosaur ancestor walking around because we have found footprints. It left a whole bunch of footprints. And it was a weird kind of animal. It was about the size of a house cat. And it walked on four awkwardly long legs.

Based on the structure of the footprint and what would be the structure of the foot, we think that this is what's known as a dinosauromorph. So this is a group of animals that would become dinosaurs later. But this is probably the very, very beginning of the dinosaur line is about 250 million years ago. Bye-bye.

But by the time we get to the late Triassic, around 230 million years ago, there are several species of actual dinosaurs. So sometime between 250 and 230 million years ago, dinosaurs really kind of take off. But it's going from like zero species of dinosaur to like, what,

eight maybe species of dinosaur. So there were a whole lot of other reptiles that were dominating at this time. And dinosaurs were just kind of, it was like a slow burn. It was a slow fuse. What's leading up actually to a massive extinction event at the end of the Triassic, which wipes away basically all of their competition, all those other weird reptiles from the Triassic and really opens the door to

to dinosaur dominance that you see in the Jurassic period. So it turns out scientists aren't sure what the very first dinosaur was.

When it comes to evolution, there isn't a single moment when a species turns a metaphorical page and then poof, it's something new. Instead, living things change very gradually and develop different features over time. Scientists try to figure out when these changes add up to a totally new species. But dinosaurs lived so long ago that the details are still pretty fuzzy.

What we do know is that there were very small dinosaur-like animals about the size of house cats around 250 million years ago.

And then, a few million years later, there are multiple species bopping around that were definitely dinosaurs. So, until scientists find more evidence, we can say that the first dinosaur was probably something like that species that left footprints behind 250 million years ago. Wow, I'd rank that a top-tier dino fact. ♪

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If you have a question, we'd love to help you answer it. Drop us a line by going to brainson.org slash contact. See you next time and the next day and every weekday. Until then, um...

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