Okay, but how terrifying were terror birds?

Scott Taylor (0:00)

Coming up on this episode of Okay, But... Birds.

Federico Degrange (0:03)

Large to gigantic terabirds are about 2 meters and 3 meters tall and 100, 120, 150 kilograms.

Scott Taylor (0:13)

That's huge.

Imagine you're standing in a grassland in South America, 10 million years ago. The grass is past your knees. It's hot. It smells like dust and like rain that hasn't arrived yet. Out on the plain, there's a herd of grazers, long necks, slender legs, something between a camel and a horse, but neither. Past them, heavier animals, rhino-shaped, cropping grass with big rodent front teeth. At the treeline, something the size of a bull is standing up on its hind legs, hooking branches down with claws as long as your hand. Low in front of it, an armored thing, roughly the shape and size of a Volkswagen.

None of it is familiar, because South America spent more than 30 million years as an island. No Panama, no land bridge, just open ocean between this continent and everything else alive on Earth. Which raises the obvious question, something is eating all of that, but what? If you pictured a big cat, that's a reasonable guess, and it's wrong. There are no cats here, no dogs, no bears, no hyenas. The entire carnivore and lineage is an ocean away.

So, evolution led to a different group of organisms filling the role that we typically think of big cats or wolves or bears filling. And one of the animals that got the job stood 10 feet tall, ran on two legs, wore coarse hair like feathers, and carried a head the size of a horse's skull with a hooked beak on the front of it. And it was the apex predator of an entire continent for tens of millions of years. Which brings us to the topic of today's episode, Okay, but how terrifying were terror birds? To help us explore this topic, I'm joined by paleontologist Dr. Frederico Dino de Grange. After the break, Dino walks us through what a terror bird's skull was actually built to do. Video on. These skulls are nuts. We also get into how many kinds there really were and what these animals looked like alive. And we talk about what happened when the ocean between North and South America finally closed. Stay tuned.

Welcome back to the podcast, everyone. I'm really excited to have Dino here today to talk all about terror birds. Thanks for joining us.

Federico Degrange (2:42)

Thanks for inviting me. Hi to everyone.

Scott Taylor (2:44)

Yeah, of course. Well, before we get into the terror part of it all, can you just tell us what a terror bird is and when they lived and where you would have run into one?

Federico Degrange (2:53)

Well, a terror bird is a group of karyami forms. Karyami forms were highly diverse during most of the Cenozoic, but they are only represented today by two species, the seriomas, the black-legged serioma and the red-legged serioma, which is the most closely related bird to this family, Forus racidae, the popularly known as a terraport.

Most remains actually comes from Argentina, from my country, but there are remains from Chile, Uruguay, Brazil, Peru, Colombia, and from the states, Texas and Florida.

Scott Taylor (3:35)

Oh, cool. I didn't know that there were Texas and Florida fossils. That's really cool.

Federico Degrange (3:40)

Those remains actually belongs to a larger terraport from Titani's Walleri, which is one of the youngest terraport known.

Scott Taylor (3:50)

Okay.

Federico Degrange (3:50)

And terraborts actually live from the Middle Miocene. We are talking about 45, between 45 and 50 million years ago, to actually only 25,000 years.

Scott Taylor (4:04)

Wow.

Federico Degrange (4:04)

And they were characterized by having narrow pelvis, slender high limbs, reduced forelimbs.

And probably what is most, the most characteristic feature is the skull. The skull of a terabort is looks like this.

Scott Taylor (4:21)

Wow. That's amazing.

Federico Degrange (4:23)

This is a real size skull. This is a 3D printing of a terabort skull, Andalgalornis, from Catamarca province. And basically what you can see here is that the big is, it's quite long, it's narrow, and it's tall, and it's hollow also. But what is actually the main feature of a terabort, of a phoros rasti, as we call it here in Argentina, is the lack of cranial kinesis. Cranial kinesis is, I have here a skull of an eagle.

It's basically the possibility to flex upward and downward, the beak regarding, I don't know if it's possible to see there.

Scott Taylor (5:16)

Yeah, I can see it moving a little bit. Yeah, the upper mandible moves a little bit up and down. But one thing I want to ask about that skull that you have, so that's a 3D printed replica of an actual fossil. Is that one of the larger species, or is that like medium sized?