With new technologies, paleontologists are starting to learn more about how dinosaurs lived by connecting them to animals alive today. Amy M. Balanoff, assistant professor at the Center for Functional Anatomy & Evolution at Johns Hopkins, joins host Krys Boyd to discuss the T. Rex and its brain – how paleontologists are piecing together what abilities they had, and why the modern housecat might offer some clues. Her Scientific American article, co-authored by Daniel T. Ksepka, is “What Was It Like to be a Dinosaur?”
- +
Transcript
Krys Boyd [00:00:00] In classic detective stories, fingerprints often play a starring role. Detectives hunt down all kinds of clues as to who done it and why. But often it’s those prints found on an incriminating object that officially closed the case. It’s not that our clever crime solving heroes are obsessed with the prints, per se. It’s just that sometimes that’s all the physical evidence they may be able to find. So it goes with paleontologists and their bones. From KERA in Dallas, this is Think. I’m Krys Boyd. We can easily picture these scientists at work on a dusty excavation site or in a lab hunched over fossilized remains of a creature that hasn’t existed for 60 million odd years. It’s not that these scientists aren’t interested in other parts of dinosaur bodies. It’s just that the bones can sometimes be preserved for many millions of years in a way that soft tissue like organs and skin cannot. So this is really exciting. New techniques and modern technology are now offering the first opportunities for researchers to gain information about dinosaur brains, how big and complex they were and what sort of sensory perception they supported. Amy N. Balanoff is here to tell us more about this. She is assistant professor at the Center for Functional Anatomy and Evolution at Johns Hopkins University and coauthor of the Scientific American Article. “What was it like to be a dinosaur?”. Amy, welcome to Think.
Amy Balanoff [00:01:24] Thank you, Krys. I’m happy to be here.
Krys Boyd [00:01:26] Just so we are all clear at the outset, we’re talking about new ways to visualize the braincase of T-Rex and other dinosaurs. Right. The idea that an actual brain from a prehistoric animal could be preserved. As far as we still know, that is impossible. Right?
Amy Balanoff [00:01:43] So I wouldn’t say impossible. I would say very, very, very unlikely. So there are a few instances where you get just the perfect conditions to preserve neural tissue, but those are usually in more aquatic settings. So in some fish, in some fossil fish, there are preserved brains. But for dinosaurs, much more unlikely.
Krys Boyd [00:02:06] So what is a natural endocast?
Amy Balanoff [00:02:10] So an endocast in general is an infilling of the cranial cavity. So that’s that space where the brain sat during life. So if you can fill in that space and get rid of the bones around that space, what you have is a cast that actually looks pretty much like a brain. And that’s because as the brain develops in things like mammals and birds, it fills the space and leaves an impression on the internal surface of the braincase. And so a natural endocast is when that happens during diagenesis. So if you have a fossil and sediments and fill the cranial cavity and then you prepare away the bones, that’s a natural endocast.
Krys Boyd [00:02:56] How rare is it to find one of these as compared with like, other parts of a dinosaur skeleton?
Amy Balanoff [00:03:02] It’s fairly rare. It’s not a common it’s not a common find in the field. Every once in a while, you you do just happen to get lucky and find a natural endocast. But. But not very often.
Krys Boyd [00:03:16] Is it that skulls are just hard to find or that the ones that have endo casts are rare among skulls?
Amy Balanoff [00:03:25] Both. So, skulls are hard to find. A lot of times skulls will get separated from the rest of the skeleton and get washed away or scavenged or whatever. It’ll get separated from the rest of the skulls. And so a lot of times it’s not easy to find a skull. A lot of times it’s not easy to find the right part of the skull that’s going to preserve the braincase. And a lot of times and a lot of times, it’s almost impossible to find a naturally occurring endocast.
Krys Boyd [00:03:58] So what assumptions did earlier generations of scientists make about the intellectual capacities of dinosaurs?
Amy Balanoff [00:04:06] Earlier generations were not kind to dinosaurs. So weren’t dinosaurs. They were because the the earliest dinosaurs that were found were these really big dinosaurs, things like sauropods. You can think of a like apatosaurus that have these giant body sizes and you know what looks like a relatively what looks like a relatively small brain for that body size. So they assumed because they had these small brains, big body sizes, that they were just not the most, intelligent of creatures.
Krys Boyd [00:04:43] For a while in the 19th century, some people thought Stegosaurus’, in particular, had two brains.
Amy Balanoff [00:04:50] Yes. So it’s so it’s so weird. Just one of those weird things about paleontological history. You have an expansion of basically the spinal cord near the near the tail. And so they assumed that. For some reason, Stegosaurus had a brain near its tail as as well as within within the skull. That was pretty pretty quickly debunked in many ways. But yeah, for a long time it was for a while at least, it was thought that Stegosaurus had two brains.
Krys Boyd [00:05:25] What actually was that other thing they thought was a brain in the tail?
Amy Balanoff [00:05:30] So it’s what you call like a glycogen body. So it probably it’s so it’s something that was use probably for for balance. But it was also you also have to think that these things had enormous hind limbs as well. So a lot of what was just an expansion of the spinal cord at that level.
Krys Boyd [00:05:53] All right. So what is this tech advancement that allows for pretty detailed study of the volume and surface structure of dinosaur brains when these natural endocasts are existent, or found?
Amy Balanoff [00:06:06] So what we’ve been able to use in more recent years is we’ve been using biomedical advancements to also advance the field of paleontology. And so one of the major biomedical advances in the last 25, 30 years has been CT scanning. And so what we can do is we can use a CT scanner, much like, you know, CT scans that you get when you go to the hospital and, you know, God forbid, if you fall and hit your head and get a CT scan, it’s the same idea for for scanning these these fossils. We simply put them in a CT scanner so that we can see the internal anatomy of the skull. They’re much more powerful. You wouldn’t want to you wouldn’t want to go through a human wouldn’t want to go through one of the CT scanners that we use. But it is the same same concept as the ones that are in hospitals.
Krys Boyd [00:07:01] Even though the fact that what you’re looking at is really solid rock, right? I mean, it feels is that why it has to be stronger than the CT scan to look at our brains?
Amy Balanoff [00:07:12] Exactly. So a lot of the fossils that we find have been what we call per mineralized. So there have been minerals deposited within the bone itself. And the spaces in the brain case have been filled by by sediment. And so, yes, you do need oftentimes a much more powerful X-ray source to get through all of that, like you said, to get through that rock, basically, and see the differences between what’s just filled in, you know, the spaces that are filled in by sediment and the spaces that are still have kind of bony structure.
Krys Boyd [00:07:55] But all this can be done without any physical damage to this precious fossil. Right? No cuts, no core samples, nothing like that.
Amy Balanoff [00:08:02] That’s what’s so great about this technology is that it is nondestructive. And so museum curators are much more likely to let you CT scan a fossil than to do. You can make an endocast and in a lab that you basically have to cut the skull and have to do it. And they don’t really like that very much.
Krys Boyd [00:08:23] So we believe now that modern birds are descended from dinosaurs. But is it not all lineages of dinosaurs?
Amy Balanoff [00:08:32] That’s right. So there is a an overwhelming amount of evidence supporting the idea that one of the dinosaur lineages survived that end cretaceous extinction and went on to become birds like we we recognize today. Some birds are dinosaurs, but obviously not all of the lineages of dinosaurs survived that, that cretaceous extinction. So it’s just this one lucky lineage that that managed to make it through through that that extinction period.
Krys Boyd [00:09:08] And that’s the theropods, the carnivores with the tiny little forelimbs and the long tails structured T rex and similarly structured species.
Amy Balanoff [00:09:18] Correct. So it is the theropod lineage that survived the Cretaceous extinction. There’s a there’s an enormous amount of diversity within that, that theropod lineage. So there are big things like T rex and small things like Archaeopteryx or Velociraptor, which relatively small. But yes, they’re that lucky lineage to survive.
Krys Boyd [00:09:41] Okay, So we have plenty of excellent birds to study today, but they seem to display a wide array of behaviors and intellectual capacities. How might CT scans help us discern where T Rex could have fallen on that spectrum?
Amy Balanoff [00:09:57] So, we can look at brain size in birds to give us an idea of what their capacity for, what their cognitive capacity was. So brain size is not a perfect measure of that, but it does give you a good idea of a kind of quote unquote, intelligence in animals. So birds that how are birds or other animals actually that have a very large brain size for their body size tend to be kind of the smarter animal. So humans have a very large brain for their for their body size. Same with parrots and same with crows. These are these are these are animals that have very large brain to body ratios and T rex, we can we can kind of do the same thing with T rex. We can kind of see where it falls along that that spectrum, whether T Rex has a very large brain for its body size or whether it has a smaller brain for its body size. And T rex is, you know, we can’t going to pick a perfect picture of how large its brain was. But given what we can what we can say using these endocasts, T Rex had a fairly large brain for its body size.
Krys Boyd [00:11:13] What might be more important even than than than the actual brain size is the number of neurons in this area of the brain known as the telencephalon. What does that region do for an animal?
Amy Balanoff [00:11:26] So the telencephalon is doing a number of things. So the telencephalon is the termination point for a lot of sensory information. So visual information is going into the telencephalon auditory information about hearing is going into the telencephalon. Sensory information about touch is also going in there. So all of these different types of sensory information are coming into the telencephalon, and that’s where it all gets assembled, basically. So all of that information comes together and that is how we and that is when we use that information to basically make decisions or plan out what we’re going to do next. And that is essentially what cognition is. And so cognition is taking place within the telencephalon and specifically within the cerebrum.
Krys Boyd [00:12:22] So we have a telencephalon. And like every animal with a brain has a telencephalon.
Amy Balanoff [00:12:27] So all vertebrates have a telencephalon.
Krys Boyd [00:12:31] What might be more important than even the the telencephalon specifically is like how many neurons a brain might have contained. How in the world would we estimate that if we have no remains of dinosaur brains?
Amy Balanoff [00:12:47] Well, that’s a good question. There are some recent studies that have tried to estimate the number of neurons within the telencephalon. And the idea is that because this is basically where most of the cognitive processes are taking place, if you have more neurons within the telencephalon, you would be a more intelligent species. So a recent study has used brain size and metabolism to try and reconstruct the number of neurons within thetelencephalon of extinct animals. And they were doing that using living animals as a model. So if you were a warm blooded, if the idea is that if you’re a warm blooded living animal, you have more neurons within your telencephalon than if you are a cold blooded living animal. And so they, they, they it’s a very complex thing of plugging things into equations. But basically, if you’re warm blooded, you have more. The idea is you have more neurons within that telencephalon.
Krys Boyd [00:13:57] So, Amy, in estimating how many neurons a dinosaur’s brain might have contained, one thing that has been helpful is the use of this tool to examine modern animals called the isotropic fractionator method. How does that work? What is it?
Amy Balanoff [00:14:14] I know it’s a great name.
Krys Boyd [00:14:15] Makes you feel smart just to say it? Yeah.
Amy Balanoff [00:14:18] It is. So basically the idea is to dye the nuclei within the cell of the neuron. And then you. You basically make brain soup. So you, you break down the neural tissue and then once you breakdown the neural tissue, because those nuclei have been been died, you can actually count the number of neurons. And so that is the that is the idea of kind of how they’ve been estimating the number of neurons in living animals.
Krys Boyd [00:14:55] So this has been used for living animals. Is the is there like a scientist sitting in a room physically counting these or is this done somehow with a computer?
Amy Balanoff [00:15:05] Yeah. So it’s it’s done. I mean, it’s it’s automated to some extent. You’re not sitting with a jar of like brain soup and trying for —
Amy Balanoff [00:15:16] It’s not quite it’s not quite to that extent but you can if you can if you can get the density of neurons within a given space, within a small space, that should be you can, you can scale that up so that you can understand how how many neurons would be in a much larger space as well. So you just need to get that density of neurons within a small space.
Krys Boyd [00:15:37] So that’s all well and good for an animal that has recently died, but we can’t use that technique on a dinosaur brain that has long since decomposed, right?
Amy Balanoff [00:15:46] Correct. No, it obviously you have no neural tissue to die. You have no cells to die. So you you have to estimate based on living animal. So you can take estimates based on what we know about living birds and living crocodilians.
Krys Boyd [00:16:05] How does an animal’s metabolism, as either cold blooded or warm blooded, tend to relate to the number of neurons it has available?
Amy Balanoff [00:16:13] So cold blooded animals tend to have fewer neurons within their telencephalon and cerebrum, then warm blooded animals do. So you would you would expect to see more. Neurons within warm blooded animals telencephalon
Krys Boyd [00:16:29] Why would warm blooded species have more neurons? Is it just take more brainpower to stay warm?
Amy Balanoff [00:16:35] Well, partially. Neural tissue is very expensive tissue. So it’s very helpful to have a high metabolism, to maintain neural tissue, to to maintain large numbers of neurons within the brain.
Krys Boyd [00:16:51] Modern birds are thought to be descended from dinosaurs. Birds are warm blooded, but so are modern crocodiles, which are cold blooded. Why can we reasonably assume T-Rex might have been endothermic or warm blooded?
Amy Balanoff [00:17:06] So we can use some clues. The this recent study that’s been done estimating the number of neurons within the brain, they actually they they made the assumption that animals with large brains for their body size would have needed to be warm blooded to support that large brain. So they used relative brain size as a way to estimate warm bloodedness or cold bloodedness.
Krys Boyd [00:17:38] So if we take that formula derived from isotropic fractionator data and we apply it to the T rex telencephalon, you get something like 3 billion neurons, which is comparable to primates.
Amy Balanoff [00:17:52] Correct. So that is a large number of neurons for a telencephalon, which. Yes, that is a very, very large number. And again, close to close to some primates. I think it’s it’s close to what you might see in a baboon.
Krys Boyd [00:18:10] One has to wonder why a T-Rex would need to be quite so smart. Even if it were warm blooded, given its like, astonishing size and speed. But that’s not the end of the story, right? It is possible that T-Rex brain cases were not entirely filled by brain cells.
Amy Balanoff [00:18:28] Correct. So brains. So I mentioned earlier that the mammals and birds tend to fill their cranial cavity, but that’s not the case for everything. A lot of times what you find within the cranial cavity with the brain are these large venous sinuses, so large sinuses where blood is draining out. Or you might find you might find large pockets of cerebrospinal fluid. So it’s not always the case that the brain is filling the entirety of the brain case. And so that’s what happens with with turtles. That’s what happens with crocodilians. And and somewhere along that dinosaur lineage, probably along that theropod lineage, you see that transition from something that whose brain is not filling the entire space to something more like a bird, where almost all of that space is being filled by brain.
Krys Boyd [00:19:30] Okay, how can we start to drill down to understand the relationship between T-Rex, brain volumes and T-Rex sensory abilities?
Amy Balanoff [00:19:39] Well, so some things to show up on the endocasts. So the endocast, this is why endocasts are so useful. It’s because we can see certain features. And so things like the old factory bulbs which are used during that are controlling the sense of smell, show up fairly well on an endocast or something like the optic tectum, which is where visual information comes and might be visible on the endocast as well. So even if we can’t necessarily get at brain size, we can look at these other features to give us clues about how these animals are using their brains.
Krys Boyd [00:20:22] You note in the article that T-Rex probably had a sense of smell that would have been comparable based on these data to modern domestic cats. How well can cats smell?
Amy Balanoff [00:20:34] Well, cats can smell pretty well. I wouldn’t say they’re there. They’re not quite to dog level. I would say dogs are better sniffers. But no, it’s an amazing. So they would they would definitely surpass us in our sense of smell. So T-Rex probably had a you know, they had a fairly good sense of smell. They were highly reliant on their on their sense of smell. So they could probably, you know, pick their head up and sniff around the environment and figure out which direction their next prey was or if there’s something to be scavenged, they’d probably be able to smell that as well.
Krys Boyd [00:21:15] Is there any way to guess whether T-Rex only ate pray that it killed with those gigantic scary teeth, or whether it might have dined on carrion the way some modern birds do?
Amy Balanoff [00:21:26] Right. That’s that’s a tough question to get at. And there’s been a lot of debate in paleontology about whether T-Rex is really a predator or whether it’s a scavenger. I it’s a tough question to get at. My best guess would be that there’s somewhere in between. I don’t think T-Rex is going to turn down a meal that if it finds laying out in the open. But it also has these things like giant, giant hind legs and sharp teeth. So you have to imagine that it’s pretty fearsome animal. Also.
Krys Boyd [00:21:59] This is not even covered in the article, but I imagine you probably know as well as anybody what is the point of those little arms that seem to have no function? They don’t seem to reach anywhere that would make them useful to the animal and yet they existed.
Amy Balanoff [00:22:17] My guess is that, you know, they they are a product of allometry. So as the body grew and the hind limbs grew, the the arms did not grow. And at the same rate they got smaller as everything else got bigger. So my guess is that they were not functional at first. They may have taken on a function later in evolutionary history, but no, they probably weren’t doing a whole lot and they probably were not adaptive for any particular function. I think there is a recent article, though, that came out saying they were there too. They were short basically to get out of the way when they were eating other things.
Krys Boyd [00:23:00] Tthey do make T-Rex is weirdly endearing to modern observers, but we can’t imagine that has anything to do with evolution. All right. What can endocast data tell us about how good T-Rex eyesight might have been?
Amy Balanoff [00:23:14] So the endocast is less informative about that than some of the other features of the skull. So it’s not just about what the endocast can tell us, but also about what the others, other structures in the skull that are sending sensory information back to the brain can tell us. So we can learn a lot from the orbits of the skull. So where the eyeballs actually sat during life. So the size of the orbits and the positioning of the orbits can can tell us a lot.
Krys Boyd [00:23:50] Do we know anything about can we guess anything about the flesh that might have been built up around them that would have enabled or obscured vision in the center or on either side?
Amy Balanoff [00:24:02] Yes. So there are many reconstructions that have been done of T.Rex one. One thing that’s nice is that the T, you can tell from the shape of the orbits that T rex eyes were were positioned more frontal. So they are almost on the front of the face like ours are. They were not sitting on the sides of the head but position more on the front of the face. And so the soft tissue you can you can reconstruct the soft tissue around those orbits based on that position of the eyeballs. And what having orbits in the front of the face does is it means that you have these visual fields that that overlap with each other, one from the right eye and one from the left eye. And this is the same thing that happens in humans. That means you get slightly different pictures from one eye versus the other eye. So if you close one eye and then close the other one, you can see that the ear, your the picture in front of you kind of moves and that slightly different image from each eye in the brain. It comes together and it actually allows us to see in 3-D. And so we can say that T Rex also probably saw in 3-D, based on this structure of where his eyeball sat.
Krys Boyd [00:25:20] Are there pros and cons to that kind of vision for a predator animal versus an animal that would be prey?
Amy Balanoff [00:25:28] So for prey, it’s probably not quite as advantageous, so you’re not looking for your your next meal in the same way that a predator would be for a predator. It’s very advantageous because you don’t have to to you don’t have to move your head at all. So something that has laterally placed eyes to get an idea of the distance of something actually has to look at it with one eye and then the other side move its head back and forth. If you have eyes that are positioned on the front of your face, you don’t have to to do that. You can just stare at an object and actually see it in 3D.
Krys Boyd [00:26:10] Why do scientists think T-Rex probably had at least some ability to perceive color?
Amy Balanoff [00:26:17] That is just based on where it sits on the evolutionary tree. So T-Rex, the closest living relative to T-Rex, would have been birds. Well, outside of outside of that group. So the closest living relative to birds you can imagine, this evolutionary tree is our crocodilians. So T-Rex is basically bracketed on the evolutionary tree by birds and crocodilians, and both birds and crocodilians have color vision. So we can make this inference that birds and crocodilians inherited color vision from a common ancestor. Now, T-Rex would have also had that would also have had that ancestor. And so we can make that assumption based on the evolutionary tree that T-Rex also was able to see in color.
Krys Boyd [00:27:13] How well or poorly, Amy, can we assume T-Rex could see in the dark?
Amy Balanoff [00:27:18] So that’s that is a more difficult question to get at. Usually when we’re talking about animals that are nocturnal and can see in the dark, they have very large eyes. The problem is with T-Rex, the orbit is not a great indicator of eyeball size because the orbit is actually much larger than what was probably being filled by the by the eyeball. But usually in we have been able to reconstruct this and other dinosaurs based on these bones that sit within the sclera are within kind of a tough fibrous part of the eyeball. These are called scleral rings. And they can actually tell us how large the the pupil of the eyeball was able to to open was able to open. So if you have a larger if you’re able to open up your pupil a large degree that lets more light into the eye. And so if you’re running around at night, it’s really advantageous to be able to let as much light as possible into the eye. So something with a very large glare will ring is more likely to be nocturnal. But unfortunately, this is not something that we’ve we found for T-Rex yet.
Krys Boyd [00:28:38] But if T-Rex primarily relied on smell to lead it to its prey, that would suggest it at least could have hunted day or night. Right?
Amy Balanoff [00:28:48] Let’s pretend. Yeah, potentially that that is the case. Yeah. It is possible that T rex was also hunting at nighttime as well.
Krys Boyd [00:28:57] Is there any way to guess based on evidence we have so far? Like how active they were when they weren’t hunting? I think about lions that, you know, they do a little bit of hunting and then the rest of the time they kind of lay around waiting to get hungry again. What do we know about, like an apex predator? Like a T rex?
Amy Balanoff [00:29:16] That’s a good question. I’m not sure that there is a good answer for it yet. You wouldn’t expect them to want to expend too much energy during the day, so they would want to reserve their energy for for hunting, much like much like lions do. And some of this would also depend on whether they were cold blooded or warm blooded. There is evidence based on histological data that that T rex was probably warm blooded. So if if that’s the case, they, you know, they don’t have to sit out in the sun to kind of renew their their energy. But we can, you know, we can use some of these clues to kind of get at that question. But I don’t know that there’s a good answer to that question yet.
Krys Boyd [00:30:04] By the way, before we move on, despite what we all heard in that original Jurassic Park movie, there is no reason to think T Rex could only see things that were moving. Is that right?
Amy Balanoff [00:30:14] That’s correct. So T Rex would have been able to, based again, on those visual those visual fields and being able to pick things up in three dimensions. It doesn’t mean that you would have to. It doesn’t mean that you would be safe if you were standing completely still. They would be able to pick you out out from a background so they could actually see your three dimensionality and pick you out from from the background. Plus they’d be able to smell you right off.
Krys Boyd [00:30:43] Amy, what can studies of their skulls tell us about T Rex hearing and balance the things that we associate with the inner ear?
Amy Balanoff [00:30:53] Right. So there are there are a couple of things, as you just mentioned, that the inner ear can do. You have the semicircular canals, which anyone that’s ever had an ear, an inner ear infection is probably familiar with, and that they are sensing rotational movements of the head and body. So that’s really controlling your sense of balance. You also have this portion of the ear called the cochlea, which is where all of the hair cells that pick up auditory or sound vibrations are located. And so both of those together, these regions can tell us a lot about the sensory perception of of extinct dinosaurs. And so. Especially that that cochlear region can can tell us about how dinosaurs, what they were hearing in their environment, whether they were hearing very high pitched sounds or much lower frequency frequency sounds.
Krys Boyd [00:31:57] Many modern birds, of course, sing. Can we make any guesses as to whether T.Rex did a very loud version of this?
Amy Balanoff [00:32:06] So there is some data to suggest that probably no, they probably weren’t singing one of the one. A recent paper came out talking about how they might have been able to hear very high pitched chirps coming from their their young. And so the one of the ideas is that. That T-Rex was able to or not just T-Rex, but really archosaurs, which are crocodilians and birds. So that group all together that their ears evolved partially to hear these high pitched chirps from their young and so that they could know what was going on with with their chicks or with what the young croc and young crocodiles. But again, using that evolutionary evolutionary history and reconstructing the ears in the same way that we do the brain endocats, we can do ear and endocasts and looking at the morphology of extinct dinosaurs, we can make this inference that they also were able to perceive these very high pitched chirps from their from their young. And so parental care probably originated fairly early in this in this evolutionary history.
Krys Boyd [00:33:32] Is there any way to guess based on crocodilians and birds today, what, like an actively involved T-Rex parent might have done for those hatchlings?
Amy Balanoff [00:33:41] So we can we can probably use T-Rex. I mean, we can probably use crocodilians as a model for T-Rex. So they’re not overly involved. So we’re not think we’re not talking about birds bringing worms to their to their young. That probably evolved that that level of parental care probably evolved much later. And in fact, we have direct this is one of the one of the coolest things, I think, is that we have direct evidence for parental care. So that level being preserved in the fossil record. So some theropod dinosaurs, this group of dinosaurs called oviraptorsaurs, we’ve actually found fossils of them, brooding nests of eggs. And so that degree of parental care probably evolved much later, but at least kind of knowing that your your younger rock evolved much further down the tree.
Krys Boyd [00:34:39] Is there any way, based on the fossil record, to guess how long it took for juvenile T rexes to get big enough that no other animal predator animal would would threaten them?
Amy Balanoff [00:34:52] So there is there are ways of getting at the rate of growth of of extinct dinosaurs. There are there are methods that allow us to take histological or thin sections of the bones of the long bones of dinosaurs. And then they actually you can count the the number of rings can actually allow you to count how old the dinosaurs are. So like trees, they, they will have a they’ll add a growth ring and you know, every, every so often so within a certain number of time. And so you can count if you can count those rings, you can actually get the age of an extinct dinosaur. And then you can estimate well, you know, you can estimate how fast it was growing. So, you know, if a very large T-Rex, you know, whether that was 20 years old or whether it was ten years old, based on these growth rings within the long bones.
Krys Boyd [00:35:58] How big were they when they hatched? Like it was it was a T-Rex egg the size of a bowling ball. Or give us a comparison.
Amy Balanoff [00:36:06] Yeah. So they probably were not very, very large. When they hatch, most eggs tend to be small. Most eggs because of the kind of the physiological constraints on an egg, you don’t get huge eggs. The the largest known eggs were actually laid by a bird. So within the living radiation of birds, the largest known eggs were were laid by these birds called elephant birds. They’re extinct birds from Madagascar. And those got up to like two gallons in size. But they are really pushing the limits of how large an egg can get. So T rex eggs would have been much smaller than that.
Krys Boyd [00:36:50] Do we have any guesses as to how male and female T rex is sort of came together to to attract one another? I mean, you know, two creatures of that size mating would have been a pretty extraordinary thing for everything else around.
Amy Balanoff [00:37:08] It wouldn’t have been it absolutely would have been. I, I don’t know of any evidence suggesting that there were any mating rituals or anything like that, like we see in birds today. So there are lots of you know, they’re lacking of birds. You see amazing displays of feathers that are definitely part of sexual selection. But I don’t know that there has been any evidence found to suggest there was anything unique about the the mating or behavior, the mating behavior, I should say, of T rex. It could it could certainly be found some day. But I don’t know of anything right now.
Krys Boyd [00:37:55] To go back to the balance structure in the inner ear, how might that have made it possible for dinosaurs to evolve into creatures that would eventually take flight as birds?
Amy Balanoff [00:38:07] Right. So the inner ear, as I mentioned before, the inner ear is a part of the inner ear is a series of semicircular canals. And there’s evidence to suggest that the shape of those canals can influence how you perceive your three dimensional environment around you. And so something like T Rex doesn’t really need to doesn’t really need to sense its its environment so much in three dimensions because it’s walking, it’s walking in on one plane, it’s not moving up and down so much. It’s going to be moving forward, backward, side to side, not so much up and down. Whereas if you are moving in a more more arboreal environment, if you’re moving through trees, you might need a more sophisticated sense of balance. And so t rex ears, their semicircular canals are fairly straightforward. They don’t reflect that, that they’re moving through any kind of very complicated environments. However, if you get to something like Velociraptor or Troodon or Archaeopteryx, these animals have a much I wouldn’t say a much more complicated semicircular canal shape, but it is a more they’re more extensive. There are longer semicircular canals. They do have a different you know, they do have a different shape from what something that you would see in a T rex. So there is a difference between the animals that are just moving along the ground versus animals that are moving through more three dimensional environments.
Krys Boyd [00:39:47] Archaeopteryx did fly, right. Is there some reason why we don’t assume that Archaeopteryx is like the animal from which birds evolved?
Amy Balanoff [00:39:56] Right? So Archaeopteryx certainly flew, and Archaeopteryx is very closely related to two living birds. It’s not the animal. It’s hard to actually pinpoint a fossil and say that is the ancestor to everything else. It’s just very unlikely that you’re going to find the ancestor. And so what we do is instead of trying to find ancestors and instead of trying to go about things in that way, we can use what we know about fossils and what we know about living animals to reconstruct, what ancestors would look like so we can use evolutionary trees. We can use the the anatomy of of fossils and living birds, in this case, to reconstruct what ancestral anatomies would have looked like.
Krys Boyd [00:40:54] How much of cutting edge paleontology, Amy, now happens in lab settings as compared with field settings like excavation sites?
Amy Balanoff [00:41:05] I would say it is a large amount. I think that a lot of paleontologists still go out into the field. I certainly enjoy going out into the field. It’s one of the great things about being a paleontologist. But almost all of the work these days is done in in the laboratory. So CT scanning specimens Doing the image processing of those CT scans so that we can make these digital endocasts. We do things like put digital landmarks so that we can quantify the shape of, of, of fossils so we can understand like how stresses were being applied to different bones. There’s so much that you can do in the in the laboratory these days as opposed to the field. And I think the field will always be a part of of of paleontology, but much, much more so these days. Paleontologists tend to spend their time in in the laboratory.
Krys Boyd [00:42:10] Can we assume now that anywhere in the world that dinosaur fossils are found? There are enough scientists nearby to ensure that they’re properly studied. I mean, sometimes you hear about, like, billionaires and Hollywood actors, like buying themselves a skeleton. Maybe there are enough to go around for all the scientists to study. I wonder what your feelings are about that.
Amy Balanoff [00:42:32] I always do wince when I hear that a fossil has sold at auction. Not only do you worry about the provenance of that of that fossil, a lot of times these are illegally collected fossils, so you always worry about that. And I’ve worked in Mongolia. And so, you know, whenever you see a Mongolian fossil for sale, I always kind of get a little worried because those are those are almost always illegal fossils. But yes, so the other thing is that. A lot of the specimens that are being sold on auction or on on the Internet are are very rare. And so some of them are very common. But that’s fine. Know, if you find a sharp tooth, it’s probably okay. I should probably shouldn’t say that as a paleontologist. But, you know, it’s not as it’s not as rare a fossil as some of the other things that are being sold. And some of these fossils are actually very rare. And so it would be it’s sad to see them not going into scientific institutions where they can be studied by scientists.
Krys Boyd [00:43:44] Do you have like a fossil find in your past that inspired your career, or how did you get into this field?
Amy Balanoff [00:43:51] It’s a really funny story. I never really envisioned myself as a paleontologist. My father taught political science. My sister actually teaches political science now. So I always thought I’d kind of go into some form of, you know, be involved in politics somehow. But I took a class my very first semester in college that was called: “The age of dinosaurs.” That’s what it was. And I was just totally enthralled by honestly by how much paleontology had changed. And it wasn’t what you saw necessarily on on TV, but that there were these other techniques that were being drawn into paleontology. And so I went to the professor after that semester and I just asked and was like, how do I get how do I get involved? And so I started working in his lab and kind of the rest is history. I just went on from there.
Krys Boyd [00:44:51] Amy Balanoff is assistant professor at the Center for Functional Anatomy and Evolution at Johns Hopkins University. She’s also coauthor of the recent Scientific American article. “What was it like to be a dinosaur?” Amy, this has been really interesting. Thanks for making time to talk about all this.
Amy Balanoff [00:45:08] It’s been my pleasure. Thank you.
Krys Boyd [00:45:10] Think is distributed by PRX, the public radio exchange. You can find us on Facebook and Instagram and listen to our podcast free wherever you get your podcasts. Just search for KERA Think. Our website is think.kera.org, and you can find out about upcoming shows there. Listen to the podcast and sign up for our free weekly newsletter. Again, I’m Krys Boyd. Thanks for listening. Have a great day.
