Dinosaur mysteries with Riley Black

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0:38Spend less time searching and more time actually interviewing candidates who check all your boxes. Listeners of this show will get a$75 sponsored job credit at Indeed.com slash podcast. That's Indeed.com slash podcast. Terms and conditions apply. Need a hiring hero? This is a job for Indeed Sponsored Jobs. How do we know what we know about dinosaurs? I think about this whenever I'm in a natural history museum because you have these bones that are tens or even hundreds of millions of years old. They come from a version of our planet that looks pretty different from the Earth that we walk on today.

1:17So how do we take these fossils and spin them into the stories about dinosaurs that I love to read and watch? The dinosaurs are dead, yet in our imaginations, they are very much alive. My guest today, Riley Black, has written a lot about how to piece together an entire narrative from fossils. Riley writes about how we know what we know about dinosaurs.

2:04Riley, thank you for being on the show.

2:07Riley Black:Oh, my pleasure. I mean, you asked me to show up and bring my dinosaur stuff. How could I resist? For our listeners, Riley brought some dinosaur models and a cast of a dinosaur hand along. But Riley, can you tell me a little bit about who you are, please, and what you do? Sure. So I'm a professional science writer. I've written about a dozen books about prehistoric life in one form or another. And I'm also an amateur paleontologist. I go out in the field and I actually find some fossils. I mean, if you are going out into the field, what is amateur about it? So there's a bit of a divide sometimes between the professional paleontology side and the many, many, many amateurs and volunteers out there looking for fossils.

2:44So I call myself an amateur because I'm not a curator. I'm not a professor. But I've been out in the field from places from Alaska to Mexico.

2:53Riley Black:A lot of work in the four corners actually finding fossils that go to museums and are cataloged and studied there. So I do it for the love of it. But why dinosaurs? It's hard not to be into dinosaurs. I mean, from what I was told, I went through a very short phase with trucks and then elephants, which I still love, and dinosaurs. So big and loud, I guess, is always what I've been kind of into. Went to the American Museum of Natural History when I was five. Heard of it. When you are small, not as small as a Mesozoic mammal, but still quite small and seeing these big skeletons, it's hard not to be impressed.

3:25And what I love about them, and really any prehistoric life, is you look at their bones or their traces or what they leave behind, and there are all these questions of how did they move? What did they look like? What color were they? What did they sound like? What did they smell like? All of the stuff that we may or may not have answers to. So it was a chance to get to know this whole realm of science that's fueled by the questions. We're encouraged to use your imagination. I think this is a perfect transition into what I wanted to talk to you about today, which is how do we know the things that we know about dinosaurs?

3:57And so I thought maybe we could start sort of where the paleontologists first started, which is the skeletons that they left behind. So talk to me about how we sort of take a dinosaur skeleton, like a bunch of bones, and turn that into a story about reptiles running through the world. I mean, this is how paleontology as a science started. I think it's important to note that people have been finding fossils for thousands and thousands of years. We have, like, stone hand axes of fossils in the indigenous cultures all over the planet have encountered fossils of different kinds and understood that these were once living things.

4:30So, like, we've had this long recognition that there was life before us. But it's the late 1700s. We have geology, which is starting as a science, and comparative anatomy, mostly in Western Europe. And you put those two things together, people find these weird bones, usually disarticulated, usually incomplete. but it's just big, big stuff. Like a tooth from a reptile that's far larger than any crocodile or snake or anything that lives in that part of the world today. And they know this must be something. And they try and slot it into what they knew. So this is why the earliest representations of dinosaurs look like giant lizards or giant crocodiles.

5:04It's just like, what's a reptile but must have been 100 feet long. And then we get more complete skeletons. They're like, oh, okay, the body shape is entirely different. Which is kind of funny. Brachiosaurus is a great example because we really only have the forelimbs and parts of the vertebra and some of the neck. And that's about it. So we're really basing it on other more complete animals. Wait, wait, wait, wait. This dinosaur?

5:24Riley Black:Yes. We have like these parts, the front legs, some of its neck. And what else? A few bits of its backbone along the spine, a couple limb elements. And there's some that I know are undescribed. There might be skull pieces. How do we make something like this from some forelimbs, some vertebra, some other bones, and a dream? Yeah, how we get to something like this, our friend Brachiosaurus here. So you're showing me right now a model you have of a beautiful long-necked dinosaur with a long curving tail, four lovely long legs, red and green coloring. For something like Brachiosaurus, where we don't have the whole skeleton, even now, we look to their closest relatives.

6:12There's a related animal called Giraffetitan that's found in… Giraffetitan? Yes. Sorry, so like… Giant giraffe. Big giraffe. Yeah, we have the arm lizard and we have the giant giraffe. Giant giraffe is more complete. And they're close enough that we know that they must have had similar bones. Like this is something like we know there are vertebrates, right, based upon the bones that we find. So when you have a vertebrate, they must also have a circulatory system and a nervous system and skin. Even if we don't have the exact fossil, we can start filling in those pieces as a hypothesis. So anytime you see a complete dinosaur, unless it's really literally that specimen or that cast that someone's made a one-to-one of, it's a hypothesis.

6:52Anyone's vision of a dinosaur, like I can say T-Rex, and the T-Rex I see in my head, it's going to be different from what you see in your head. And this is what I love about it is that we're taking sort of this bare scaffolding and based upon what we know and what we see from experience, filling in like what might have been there. What are some of the most interesting or maybe even counterintuitive ways that we have been able to say, no, I'm pretty sure this looked this way just by looking at the bones alone? So the bones alone, usually we need a complete skeleton or a fairly complete skeleton to tell.

7:23But this little T-Rex hand that I brought in is really good. example. This is an animal that would have been more than 30 feet long, and you can hold its hand in your hand. It would have been an arm about as long as yours. So I'm looking at, just to be clear, sort of what looks like two fingers of a T-Rex hand that have very pointy claws on the end of them. And you actually have a little bit of a third finger there. So there's a little splint bone that's underneath the larger fingers. And that third one, that splint is the remainder of the third finger. We always make fun of T-Rex for having tiny, tiny hands, right?

7:59Well, they used to have three fingers and their ancestors lost them. Okay, so this tiny little bone, this bone that's actually the size of my pinky, is like an ancestral third finger, like a tailbone of a third finger that they have.

8:13Riley Black:Right, which was lost. And we didn't know that. So when the first Tyrannosaurus Rex was being reconstructed here in New York City, we used to think it was related to other carnivorous dinosaurs that we knew about. But there was no arm. You know, we had the big old skull. We had the backbone, ribs, all this stuff. No arms. The arms are tiny. Of course, they'd probably wash away and not get buried. It wasn't until someone actually found a T-Rex arm with the hand at the end of it. So early on, they thought, well, it has to be fingers like all the other carnivorous dinosaurs do. And then someone found a related form in Canada and Alberta that only had two.

8:44And we know that they were closer to T-Rex. It's like, okay, we have to change the model. And that's why T-Rex has two little fingers. Fascinating. Okay. Okay, so finding bones, finding more bones to complete out a skeleton can really tell us, like, oh, we got this wrong, we got this wrong, etc. But you also had an article that you wrote that was also about tiny arms that was a little different that I loved. Can you tell me a little bit about Alvarezaurus? Am I saying that right? Yes, yes, the Alvarezaurus.

9:14Riley Black:I'm glad to talk about them because nobody talks about Alvarezaurus. This is like the indie band that, like, only does vinyl. So let me pull up a photo. Yeah, show me a picture of Alvarezaur, please. This is a little critter called Mononychus. Oh, this is Mononychus. And it belongs to a group called Alvarezurs. So I'm looking at this very small, very cute creature that has very long legs. It has a really long neck. And then it just has these rinky-dink little arms coming off of it that it's holding together in a little... Oh, like a little please, like a begging posture. Like, can I go home an hour early?

9:50Riley Black:kind of pose. That's just one claw. That's what its name means is one claw. So what is its one claw for? We don't know. We don't know because the skeleton can't really tell us exactly what it's for. Right. In that it can give us the range of motion and we can reconstruct the musculature and things like that. But it can't really tell us like, well, what did it use that musculature for? How did it move those limbs? If we know it has a short range of motion, then to what purpose, what function. Are there ideas? Do people have theories? Okay, I love a theory. So my favorite one is that these were dinosaur anteaters, because they often have either no teeth or very, very, very small teeth.

10:33And this is something that we see happen with like a shift away from carnivorous foods and more towards like insects and plants and things like that. But we think that they were like anteater dinosaurs using those little claws to basically stick their chest to the ground and just kind of scratch away at ant and termite mounds, which you know were around at the time. We actually find dinosaur bones sometimes with termite damage to them. So theory one is they were anteaters, just like poking their fingies in there. What are the other theories for what these tiny claws could be for? They might have been for grasping eggs.

11:05There was a species that was named a few months ago that they thought that they were just

11:10Riley Black:kind of clasping eggs to their chest. They're just kind of doing a little dip, picking up an egg and kind of skittering away with it. Okay. And that's really about it so far. We don't really like it. You look at that stubby arm, it's just kind of like, what? And there's not a whole lot else. We don't have a lot of equivalence for arms like these other than animals that dig into the ground somehow. Okay, so we have T-Rex claws. We have Alversaur claws. Are there other sort of dinosaurs where we're just sort of like, well, we have a bunch of bones. What could this possibly be? What does it look like?

11:44Like, so dinosaurs love their bizarre structures. Like the fashion through the Mesozoic was just something else. Like the ornamentation on these animals constantly. Like our little triceratops friend, even though that's a very traditional, you know, three-horned face look. There are lots of horned dinosaurs with all these different arrays of horns and spikes and hooks and everything else that help them differentiate each other. And that we have a fair handle on. But in terms of ornamentation, there are dinosaurs with like sails on their backs. And we have no idea why. Sails? Yes, sailback dinosaurs.

12:17So there's one in particular called Oranosaurus. This is an herbivore. So everybody knows Spinosaurus. That got its name for the spines on its back. We're doing indie dinosaurs here. We're not doing Spinosaurus. Spinosaurus can be like the it girl, like on the cover of Nat Geo. We're doing, again, the deep cuts. So this is an Oranosaurus. It is something related to Iguanodon, or the duck-beaked dinosaurs. And it has a sail on its back. Okay, so I'm looking at it. So a dinosaur, it's very difficult to describe. So the middle part of it sort of looks like a regular dinosaur. And then on its back, it just has like a whole fan of bones coming out.

12:57So I see what you mean now about a sail. What? I feel like I know the answer, and the answer is we don't know. But what's the sail for?

13:09Riley Black:We don't know. Amazingly. There have been a few ideas. one of which one of my favorite sort of discarded hypotheses is that we see these long neural spines so these flat bones that come up off the backbone in things like bison or various mammals and they usually hold a hump or the end of a ligament that goes from the back of the head to between the shoulders because a lot of these mammals have big heavy heads they need like an extra basically rubber band to help them keep their heads up and we used to think that this was true for the dinosaurs as well but then you'd have this basically mound-shaped dinosaur with If you imagine like a little hill with legs kind of shuffling around, that's more or less what they would look like.

13:47But that was one of the ideas, that this is some sort of head support or something like that. Okay. What seems more likely is it's some kind of billboard, basically. It's dinosaur advertising that they're communicating to other members of their species. What? Saying like, I'm bigger than you or I'm an adult or I'm a juvenile or like different dinosaur sexes. Like a peacock tail almost. Yes. But on their— A permanent peacock tail on their back. Yes, always peacocking in the early Cretaceous. Yeah, and with something that's that big and that elaborate, and it takes energy to grow, right? This is an investment this animal is making.

14:22Bone is constantly remodeling itself. It must have had formed some purpose in this animal's life. But unless we can see these dinosaurs interact, it's very difficult to tell what they were doing. Now, there's some ways that maybe we can get at it. We can find some skin and find out what color that skin was, which is the thing we can do now. Maybe we can start to get at it. But again, it takes the luck of the fossil record to actually make such a find. Got it. So if you could find, like, skin from another part of its body and then skin from this sail, and the skin on the sail was, like, neon, and the skin on the rest of its body was, like, fairly gray, it would be relatively clear.

15:00And the neon sign said, like, two for a dollar at Spinosaurus land. You'd be like, oh, it's a billboard. Yeah, I got that vaporwave aesthetic going. on the sail. Amazing. So what you've told us to this point is essentially that skeletons can't tell us everything we need to know. Bones are not the be-all and end-all. We still have a lot of questions. We have questions about the sails on dinosaurs like Orinosaurus or even Spinosaurus or what Alvorsaurus use their claws for. What else can we look at to understand dinosaurs in more depth. Yes. So you're getting to one of my favorite kinds of fossils, and those are trace fossils.

15:41Trace fossils. Yes. So these are things that animals leave behind in the fossil record. So it's not the tooth of the bone or whatever itself, but it's the marks that animal made in life. So we're talking about things like tooth marks and tracks and fossil feces and all these other things that basically an animal leaves behind just through living.

16:03It's interaction, it's behavior. So like when you see a dinosaur trackway, it's not just footprints in the rock. That is moments in that animal's life. And we can calculate like how tall it was, how fast it was moving, maybe the direction it was going in. Is there another animal nearby? Is it going in a certain direction like to get around an obstacle or to avoid something? So these are actually like moments of prehistoric time that we still have as fossils.

16:30More on that after the break.

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19:12What's your, like, what's one of your favorite? You're already pulling out the phone to show me something.

19:17Riley Black:Well, now I get to brag a little. I get to talk about stuff that I have found out in the field. All right. What's one of your favorite traces? One of my favorite traces. So what I'm showing you on the phone is it kind of looks like multiple toes there. You can see one, two, three, four. Yes. And then there's a couple small toes next to it. So it's basically the front foot and the back foot of a crocodile-like armadillo thing called an aedosaur. Okay. Aedosaur. How do you know just is it like that's what matches up that footprint? Yeah. So you can look at the skeletons and you can look at what other animals are found in that formation and see kind of whose foot matches what print.

19:55It's rarely one-to-one. Okay. Unless an animal literally dies in its tracks, which sometimes does happen. It's hard to be 100 % certain. But in this case, the hand and foot anatomy matched this armadillo-like crocodile relative that was an herbivore that was living around when dinosaurs were really small. And just kind of, it looked like the ground was giving me a high five. It was like impossible to miss. And so how did you find this? Yeah, so I was out on an expedition with the Naturalist Museum of Utah out in the eastern part of the state. So like outside Arches National Park, that kind of area.