Paleontologist Answers Fossil Questions

WIRED

Paleontologist and Geologist Dr. Ken Lacovara joins WIRED to answer the internet's burning questions about fossils. Can we extract dinosaur DNA from fossils? How is crude oil made from fossils? Where are the most common places to find fossils worldwide? How can you give yourself the best chance to become a fossil after you die? Did we ever find the crater from the asteroid that killed the dinosaurs? Answers to these questions and plenty more await on Fossil Support.  Director: Justin Wolfson Director of Photography: Chris Eustache Editor: Richard Trammell; Alex Mechanik Expert: Ken Lacovara Line Producer: Jamie Rasmussen Associate Producer: Paul Gulyas; Brandon White Production Manager: Peter Brunette Production Coordinator: Rhyan Lark Casting Producer: Nick Sawyer Camera Operator: Lauren Pruitt Sound Mixer: Brett Van Deusen Production Assistant: Quinton Johnson Post Production Supervisor: Christian Olguin Supervising Editor: Erica DeLeo Assistant Editor: Billy Ward

Transcript

00:00I'm Dr. Kenneth Lacovara, paleontologist and executive director of the Edelman Fossil Park

00:05of Rowan University, and I'm here to answer your questions from the internet. This is Fossil Support.

00:14Jenny Flyrocks asks, do you know how Tyrannosaurus head is too big for the rest of her? Is it me?

00:21Well, no, it's not you. It has a really big head. It needs a really big head because

00:26this Tyrannosaur, Tyrannosaurus rex in particular, had the strongest bite force of any land animal

00:32probably ever. And to have a really strong bite, you need a really big skull that can

00:37house really big jaw muscles. And it turns out that head muscles and arm muscles compete for

00:43attachment space around the girdle of the shoulder. So as T-Rex's bite got more ferocious, its head got

00:50bigger, its neck muscles had to get bigger. It needed to occupy more space on the shoulder for

00:56its neck muscles. Its arms got shorter and shorter and shorter. So those comical little arms that T-Rex

01:02has with two little witchy fingers is what made possible its murderous bite.

01:07Laura Bedrosian writes, can you comment on the science behind extracting dino DNA from mosquitoes

01:13in amber? Is that just Jurassic Park stuff? Yes, it is. Amber is actually a terrible geochemical

01:20environment to preserve DNA. People have looked and no DNA from dinosaurs has yet been recovered.

01:25It seems to be too old, at least for existing technology and or samples.

01:31Clipped Wings 22 writes, how do fossil bones fossilize? Are they just filled with air or are

01:36they somehow filled with the same rock that surrounds the fossils? The latter. They are filled

01:41with the same rock that surrounds the fossils. Here is a fossil pterosaur bone from Morocco.

01:47It's Cretaceous age. You can see that there is sediment inside the hollow bone of the pterosaur.

01:52And so what usually happens is the same rock that is surrounding the fossil also gets inside the

01:58fossil and it's preserved that way. Holton Music Man writes, how do fossils for fossil fuel end up two

02:03miles beneath the surface, especially enough to make oil? The fossils have to be buried in what we call

02:09a depositional basin. Think of a river valley or a continental shelf off of a coastline. As sediment

02:15accumulates in those basins, the weight of the rocks pushes them down. So they settle under their own

02:22weight. The pressure increases, the heat increases, and eventually those organics can turn into fossil

02:28fuels. Just call me Al asks, you know what's so effing cool? The evolution of discovering what

02:34dinosaurs look like through the years. Well, it's true, you know, and our understanding of the way

02:39dinosaurs looked and behaved has been evolving ever since we discovered dinosaurs. When dinosaurs were

02:44first found in the mid part, early part of the 19th century, we didn't know what they were.

02:49Scientists didn't understand them. They thought they were these big, slow lizard-like creatures.

02:54That's how they were first reconstructed. In 1858, the world's first nearly complete dinosaur

02:59skeleton was found in southern New Jersey, just eight miles from here. And that's when we first

03:03started to get our view of dinosaurs as these vigorous creatures. But they were still constructed

03:08as these kind of living tripods. You always saw the bipedal ones with two legs on the ground and then

03:13their tail resting behind them to kind of prop them up. And then in old reconstructions,

03:18you see the giants, the sauropods, are always languishing about in swamps as though they

03:23couldn't support their great weight with their own limbs, that they needed the buoyancy of water.

03:28That's not true. The giant dinosaurs like Dreadnoughtus or Argentinosaurus were perfectly capable of

03:33walking on dry land with their four great limbs and holding their neck and their tail horizontal to

03:39the ground. You know, one evolution that has happened just within most of our lifetimes is we can see it

03:44in the Jurassic movies. So in Jurassic Park in 1993, the idea that the meat-eating dinosaurs had

03:50feathers was really just emerging. So you see the velociraptor, it's scaly and it's also very,

03:55very big. Velociraptor in life was lavishly feathered, a fully feathered dinosaur. And it

04:01was tiny. A velociraptor skull is about that big. A velociraptor is more like a pissed off turkey

04:06than a giant monstrous dinosaur. If you have a velociraptor in your kitchen, it's more of an

04:12opportunity than a problem. The big nasty one writes, how exactly is crude oil created from

04:17fossils? Having a hard time wrapping my brain around that biological process. Well, it starts

04:23with the smallest organism. Some people think that oil comes from dinosaurs. Fossil fuel doesn't come

04:29from dinosaurs. It doesn't come from some of the largest creatures. It actually comes from some of the

04:34smallest. It comes from plankton. Things like diatoms and foraminifera. And as they rain down

04:40from the oceans or in deep lakes, the layers accumulate. And then they have to be buried.

04:45They could be buried by more organic material or they could be buried by sand or mud. And then the

04:50pressure begins to increase. The heat begins to increase and they start to cook. And they turn into

04:55what we call carogen. Carogen is a hard component of rock. It's the organic component. And if that is

05:02heated and squeezed in just the right way, it can turn into either petroleum or natural gas.

05:08Geology Johnson writes, what are the oldest fossil bones? Google says it's a 400 million year old

05:14fish. Are bones really that young? Geology Johnson, I really appreciate your deep time perspective

05:20because while 400 million years may sound old to most people, it's really not. If you look at the

05:25history of complex life the last half billion years, that's only one ninth of earth history. And yes,

05:31it's true that the first ossified bones appear in the Devonian period about 400 million years ago.

05:37And the first function of bones was not to create skeletons. It was probably as a reservoir of

05:45minerals. If you're living in the ocean and the ocean chemistry is fluctuating from one state to

05:50another, you're going to have a tough time getting the minerals that you need to run your metabolism.

05:55Think of bones as a chemical battery for organisms. You can deposit minerals in a bone and then later

06:03you can withdraw minerals from that bone. It's only later that bones start to serve the function

06:07of support as skeletons like we have today. The Strunk Orange writes, how do museums make the display

06:14models for their fossils and how accurate are the displays to their fossils? I can speak best about what

06:21is happening here at the Edelman Fossil Park Museum. Our sculptor who did all of our recreations upstairs

06:28first starts with a one-tenth scale clay maquette of the creature he is attempting to reconstruct. And then

06:34he 3D scans it and then he uses a CNC machine to print out slices of it. And that might be for a creature

06:40that ultimately is 55 feet long or so. And then all those slices are glued together and then he puts resin

06:46or other material on top of it and then sculpts the scales individually. He says, you know, you just

06:52start at the tail and you start sculpting scales and then a couple hundred thousand scales later,

06:57you're done. And then it comes down to some really artistic judgments about it. What were the colors?

07:04What are the ornamentations? Were they shrink wrapped? Were they blubbery? A lot of that stuff we don't know,

07:10but what we do is we use modern analogues. So for example, upstairs we have a reconstruction of a baby

07:16hadrosaur. Now, we don't know what color baby hadrosaurs were, but what we did is we looked

07:20at what color and what is the patterning of a small forest herbivore and we looked at baby tapirs.

07:27So we gave it the colors and the pattern of a baby tapir, hoping that would at least get us a little

07:32bit closer to the truth of it. As far as the soft parts that the animals have, imagine like the

07:37coxcomb of a chicken or the wattle of a turkey. Those things don't preserve. And dinosaurs and other

07:42creatures must have had amazing and extravagant soft parts that we will never know about. A couple

07:48years ago when the Apple TV series, Prehistoric Planet was about to come out, the consulting

07:52paleontologist contacted me and he said, we wanted to illustrate the point that there are all these

07:57soft tissue features that we may never know about. So I decided to give Dreadnoughtus pop-out air

08:03bladders in its neck. And so in the show, you see Dreadnoughtus and then you see these pop-out air

08:09bladders and he said, I'm sorry about this. It was my decision and I realize you're going to have to

08:14answer the neck bladder question for the rest of your days. And that is actually true. Every time I

08:20give a talk now, I get the neck bladder question and we have zero evidence that Dreadnoughtus or any

08:25other dinosaur had neck air bladders, but it is an illustration of the point that they probably had

08:31fantastic structures that will never be preserved in the fossil record. Dino4x4 asks, what's your favorite

08:38example of convergent evolution? Well, convergent evolution means that organisms have landed on

08:44the same adaptation, even though they didn't inherit those features from a common ancestor.

08:50So think of the wings of a pterosaur and a bird and a dragonfly. They all have wings,

08:55but they did not get them from a common ancestor. They evolved them independently because they were

09:00adapting to similar challenges. Think of the dorsal fin of a killer whale and the dorsal fin of a shark.

09:06Didn't get them from the same ancestor. You can see this in dinosaurs. You can see it in a creature

09:11like Spinosaurus, which has a crocodile-like skull. Not a crocodile, but it's a fish eater,

09:16as are many crocodiles. And so it's adapting to a similar situation. And so the evolutionary record

09:21in biology today is just replete with examples of convergent evolution. Caffeinated Caddy writes,

09:29did you know there's a dinosaur named Dracorex hogwartzii? Yes, that was named by a paleontologist

09:36named Robert Bakker in this museum. We have a replica of a skull on display. Dracorex hogwartzii

09:42is a bit of a controversial dinosaur. There are many paleontologists that think it's actually a

09:48juvenile form of this dinosaur right here called Pachycephalosaurus. Either way, whether it's a

09:53juvenile Pachycephalosaurus or its own species, it's incredible. It's an amazing skull. This thing

09:59looks like a dragon. Funked Up asks, how would I give myself the best chance at becoming a fossil

10:07once I die? Well, you need quick burial, right? You can't hang around on the surface where you're going

10:12to weather away or become scavenged. You need to have yourself buried in what we call a depositional

10:18basin. So that's a place where sediment accumulates. Don't try this on a mountaintop,

10:22because mountaintops are erosional and you will never, ever turn into a fossil. To preserve

10:27flesh or soft tissue structures, you want to be in an anoxic environment, meaning one that lacks

10:34oxygen. That way, the microbes won't decay the flesh. If you want to preserve the bones,

10:38you want a lot of iron in the system. So the iron that's dissolved in the groundwater can go through

10:44and mineralize out in the bones and it helps stabilize the bones and it turns them into a really

10:49resistant kind of material. Don't try to become a fossil in California or Costa Rica or in Iceland,

10:56because those are tectonic or volcanic areas. You want to be in a place like like the bayous of

11:02Louisiana or the pine barrens of New Jersey or maybe the swamps of North Carolina. Places that are

11:09very environmentally quiet. So nothing is going to disturb that body as it's underground, sitting

11:15there for millions of years. Hughes Matt writes, how are dinosaurs size and shapes determined from

11:22largely incomplete fossils? Anyone know the answer? Yes, I know the answer. It's true. Most dinosaur

11:28species are known from partial skeletons. So for very few dinosaurs, do we have the entire anatomy

11:34represented? So what we do is we work with close cousins when we don't have a particular part of

11:40the body present. For Drednautus, for example, we only had two of the probable 13 vertebra in its neck.

11:48And so to estimate the length and the proportions of its neck, we used a close cousin from northern

11:54Patagonia with the unlyrical name of Futalachnosaurus. But that dinosaur was discovered with a nearly

12:01complete neck. And so we used that. And then we had very little cranial material for Drednautus. We

12:06just had a little piece of premaxilla and a single tooth. So we used another close relative that was

12:12known really only from a skull. Drednautus, on the other hand, has a nearly complete tail section. So

12:17other scientists that are working on this group called the Titanosaurs, who find no tail bones or

12:23just a couple of tail bones, are probably going to use the tail of Drednautus then to fill in the blanks.

12:28And so we use close cousins whenever we can. It's me, Michael, writes,

12:33How do we know what dinosaurs ate exactly if only their bones were fossilized?

12:38Teeth. Mostly teeth. We can really tell a lot about an animal's diet from their teeth.

12:44This is a crocodile called Thoracosaurus. It lived in the Cretaceous period. It was actually a survivor

12:49of the extinction. So it lived a little bit after the Cretaceous as well. But look at these teeth.

12:53They're not good for anything but murder. These little spikes here are good for piercing flesh.

12:58And you see the way they're curved back like a gaff hook. It's a fish eater. And so

13:03these teeth are meant to both puncture the fish's body, but also to keep it from swimming back out.

13:08So they all point backwards towards the gullet. If you look at a different kind of crocodile,

13:13this is a very rare crocodile. This one's called Bodasaurus. And look at this tooth. It has this blunt

13:18end. And this is a shell crunching crocodile. It's picking up crabs and maybe snails and things like

13:25that and crunching them between these anvil-like teeth. Here's a little shark tooth that have

13:30serrations along the edge. So that is clearly meant for ripping flesh. So teeth are one way.

13:36Coprolites are another. Coprolite is a fancy word for fossil poop. We have a coprolite here.

13:42It's from, we think, either a turtle or a crocodile. And what you can do with these is you can slice

13:49them open and you can literally see this animal's last meal. So it's direct evidence of diet. We can

13:55also look at the isotopic signatures of teeth and bones. That can tell you what type of plants

14:02it was eating. It can tell you if it lived in a tropical or a temperate environment. And you can

14:07look at things like nitrogen isotopes and that can tell you where it was in the food chain. And so we

14:14can tell if it was a prey species that ate only plants, if it was an omnivore, or if it was a predator.

14:21Next up, what's your favorite dinosaur? Well, I would say it's one that I discovered and spent about

14:2710 years of my life working on, which I named Dreadnoughtus. And I say that because it really

14:31kind of became a member of the family. So much of our world for that time revolved around Dreadnoughtus.

14:37My son grew up with Dreadnoughtus. But I would say my favorite dinosaur that I didn't discover is

14:43Spinosaurus, which was found in the Bahariya oasis of Egypt about 125 years ago. And it's this amazing

14:51predatory dinosaur. Think of a T-Rex, but kind of one that's been stretched out with a crocodile head,

14:57long arms with gaff hooks at the end of it. And then it has these huge six-foot neural spines,

15:03which most people interpret as sails could possibly be a hump as well. But this thing lived out in a

15:09mangrove ecosystem in what is now the middle of the Sahara desert and ate fish, probably some big

15:14fish out there. I would say maybe though my favorite fossil overall is not a dinosaur at all,

15:21but it's one from the Cambrian period from the high Rockies in Canada called Picaea. And Picaea is a

15:27little tiny worm-like creature. It's about a centimeter and a half long. It doesn't look very

15:32tough. It's soft and squishy, but it has some really interesting features. Picaea has its sensory

15:38organs concentrated anteriorly. It has bilateral symmetry. It has a one-way digestive system,

15:44which I happen to think is the best kind of digestive system. It has V-shaped muscles. Does

15:49that sound like anybody you know? That sounds like everybody you know. And so if it's descendants,

15:54don't make it out of the Cambrian. There will never be vertebrate animals. There will never be fish or

15:59wombats or hoary bats or camels or dinosaurs or hamsters or you. Worthless hope, first of all,

16:07that's sad. It asks, which continents or areas are the best for finding fossil records? And why is

16:13that so? Well, it depends on what you're looking for. First, you need rocks of the right age. If

16:19you're looking for dinosaurs, don't look at rocks that are older than 237 million years old. You

16:24won't find dinosaurs. They have to be sedimentary rocks so that a fossil can form. You won't find

16:28fossils in an igneous rock or a metamorphic rock. And then today, not then, but today, it needs to be an

16:35arid environment so that you get good exposures of those rocks. That's why you usually see us

16:40paleontologists working in deserts and in badlands because you can see the rocks. And especially in

16:44badlands, you get enough precipitation that it doesn't grow plants that cover the rocks,

16:48but there's enough water in the system to cause erosion, which pushes back the hillside,

16:53always exposing new bones. So you find those three things and really you just walk until you see a

16:58fossil sticking out of the rock. That's how we do it. We never just dig a hole and hope to get lucky. We get

17:03ourselves in the right geological context and then we prospect just by walking. Specter's Knight

17:09writes, what's the best preserved dinosaur fossil that's been found? Well, I would have to say

17:14Borealapelta from the tar sands of Alberta. This is a nodosaur which falls in a bigger group,

17:20ankylosaurs, armored dinosaurs, and it was preserved in 3D. And so you can walk into a room with this

17:27dinosaur and it's like you're in a room with a dinosaur. You can see the armor, the scales on

17:32this thing. It's just incredible. There's even some traces of pigment preserved and it looks like

17:37it had what we call counter shading like you can see in sharks and whales. So it was darker on top

17:42and lighter on the bottom. It's found in marine sediments. Even though all dinosaurs lived on land,

17:48oftentimes nearshore marine sediments do have terrestrial fossils. These are what we call the

17:53bloat and float dinosaurs. They die on a beach. They get swept out to sea. At first they sink,

17:59but the body fills with decay gases. They float out to sea like a giant rotten meat buoy. And as

18:06the carcass decays, parts of the skeleton start to drop to the seafloor. Jack D. Wyss writes,

18:12how long does it take to form a fossil? Not long. The organism has to be buried very quickly

18:17and the bones have to be stabilized by minerals very quickly. A process that maybe only takes

18:24weeks or months. Because think about it, if it took a long time, then the processes of decay

18:29and degradation would destroy that carcass before it turned into a fossil. Vicks Link writes,

18:35scientists study fossilized raindrops to learn about the Earth's atmosphere. Who ever thought

18:41raindrops could fossilize? It's amazing, isn't it? The geological record preserves the longest spans of

18:47time but also sometimes almost the shortest spans. Raindrops can be preserved. Individual footsteps can

18:54be preserved. The landings of birds and pterosaurs can be preserved. Imagine how long it takes for you

19:00to make a footprint on the beach, right? Just a second. And if conditions are just right, that event

19:05that occurred for one second could be preserved for a hundred million years. It has to be undisturbed

19:11naturally for a small amount of time. The chance of it happening is almost zero. But we get to do

19:16the experiment so many times and deep time is so vast that even something that has an almost zero

19:23chance but not zero chance of occurring ends up happening a lot. There's a quote that I love

19:28that goes, unlikely things are likely to happen when happening happens a lot. SpiritualPie8298 writes,

19:37How can we guess from fossils how animals and other creatures from millions of years ago live,

19:42behaved, etc. And can we at all? Yes, we can. And more than guess. You can certainly see what kind

19:48of food an animal ate from its teeth and the way its jaws hinged and the way they were processing food.

19:53You can look at the feet and the hands. If you have an eight inch sickle claw like Dryptosaurus,

19:59well you know that thing is a flesh ripper and it was using that to eviscerate its prey. You're not

20:03going to see an eight inch sickle claw on something that's eating salad all day long. You can tell a

20:07lot about an animal's lifestyle from its posture. Dinosaurs' feet are hinged for straight ahead

20:12forward motion. You know these were active, vigorous creatures. Contrast that with the languid,

20:17sprawling posture of something like a lizard or a crocodile with elbows and knees bent, belly

20:23touching the ground, tail dragging behind. A crocodile is always about a half a push-up away from

20:27taking a nap. Wetworks76 asks, do you think all the dragon mythology was the result of ancient

20:34civilizations finding dinosaur fossils or are dragons real? Well, I don't think dragons are real, although

20:41there are some creatures like pterosaurs or Dracorex, a dinosaur that look a lot like dragons. But I think

20:46what's really happening is that ancient people are encountering fossils. They don't have any context,

20:51they don't have any structure to interpret what they're seeing. And so they generate stories like

20:56humans do to explain their observations. There's a woman named Adrienne Mayor who studies folk

21:02paleontology and she believes that the legend of the griffin, which has a lion's body and an eagle

21:08head, comes from observations of the fossils of Protoceratops. She also thinks that the legend of

21:14the Cyclops maybe comes from miniature elephants that used to live on the Isle of Crete. And if you look

21:21at an elephant skull, they have their nose holes, their nares, coalesce together and it's

21:25way up here high on their head. It looks like it has a giant eye hole right in the center of its

21:31head and thus perhaps the legend of the Cyclops. Aether Gorilla wants to know, dumb question,

21:37but why are Mosasaur teeth so common? Not a dumb question. And we have some right here. In fact,

21:42we commonly find them out there in our fossil quarry. There are many more Mosasaur teeth than there were

21:48ever Mosasaurs. Mosasaurs had a lot of teeth. They produced them throughout their lifetime. And Mosasaurs

21:54lived in places where sediment accumulated. And so when they would shed their teeth or when the

21:59whole animal would die and their skull would get buried, it was much more likely for those teeth

22:04to get buried, giving them a chance at turning into fossils. Trebor Rhubarb writes, they also tell

22:10us the pterosaur, basically flying dinosaur, didn't evolve into birds, but the dinosaurs, basically

22:15non-flying dinosaurs, did evolve into birds and they expect us to believe this rubbish. No, please don't

22:22believe it because science is not a belief system and science does not require your belief. However,

22:28we have a lot of evidence, I would call it a mountain of evidence now, that birds are in fact

22:34dinosaurs. We can see it in the evolution of their skeletons and we can see it in preservation of

22:39feathers, actually, that go along with some of these skeletal finds, that the first avian dinosaurs

22:45evolved around 150 million years ago. And we have a really beautiful record now of the transition from

22:50non-avian to avian dinosaurs leading right up to the birds today. A parakeet, a penguin,

22:56a ruby-throated hummingbird is a dinosaur to the same degree that a stegosaurus or a t-rex is a

23:02dinosaur. Being a dinosaur, just like being a mammal, is a binary condition. You can't be half a mammal,

23:08you can't be half a dinosaur. Birds are dinosaurs. Terosaurs, on the other hand, flying reptiles,

23:14not dinosaurs. It's a branch called ornithodira and the ornithodirans branched off before there was the

23:20first dinosaur. So if they don't have a dinosaur in their family, they're not a dinosaur. News

23:24Participant writes, do scientists have dinosaur DNA? Can you get that from fossils or hmm? We do

23:31not have dinosaur DNA. DNA is a water-soluble molecule, so it doesn't hang around that long

23:36in geological time. The oldest DNA that's been recovered from an individual is about 800,000 years

23:42old and the oldest DNA from the environment is about a million and a half years old. That sounds old,

23:48but that's a long way from dinosaur time, which is 66 million years ago. So we don't have dinosaur DNA,

23:54but what we do have are dinosaur proteins and blood vessels and some other biomolecules from

24:01dinosaurs. If that's an S, how big were dinosaur eggs? They were all little. This giant dinosaur

24:06that you see over here, Drednautus, which I found in South America, that grew to be 65 tons and its eggs

24:12would have been, you know, no bigger than maybe an ostrich egg. All dinosaurs when they hatched were

24:17no bigger than about the size of a large house cat and some were even a lot smaller. And I think

24:22that's actually kind of one of the secrets to the success of dinosaurs. Us mammals, we scale with

24:28adult body size. A baby elephant might be 300 pounds, a baby blue whale might be 6,000 pounds, but all

24:34dinosaurs start off small. So a baby Drednautus like that is in its environment and it's doing tiny herbivore

24:41things at first, like rabbit-sized things. Then it's doing sheep-sized things and cow-sized things

24:45and elephant-sized things and then herd of elephant-sized things. So this one species is able to

24:50capture this entire column of resources from the ecosystem. I think that has something to do with

24:56the amazing success of the dinosaurs. Spooky By- says,

25:01Sometimes I think how tortoises and gators, crocodiles, are so close to being dinosaurs

25:06and it makes me emotional. Look at them go. Well, I'm super glad you like turtles and crocodiles.

25:12I like them too, but they are not dinosaurs. Crocodiles are the closest living relatives to

25:17dinosaurs today, but they don't have a dinosaur in their family tree, nor do the turtles. And if you

25:23don't have a dinosaur in your family, you can't be a dinosaur. So they're living cousins of dinosaurs

25:28today. The only dinosaurs alive right now are birds. So if you love turtles and crocodiles,

25:33you should love birds as well because they are dinosaurs. Miguel Wildlife wants to know how to

25:38know if a fossil was a juvenile or an adult. We can look at what we call the bone histology,

25:44where you can look at the bone cells, you can see how ordered they are, and you can plug that

25:48into a formula and you can get what we call percent senescence. So this giant dinosaur over here,

25:52Drednautus, when it died, it was 65 tons, but we got a real shock when we looked at the bone

25:57histology. We could see that at the time that it died, it was growing rapidly. We honestly don't

26:02know how big these things could get. Another way to do it is you can look at the anatomy of the bones.

26:07Some dinosaurs, like some hadrosaurs, are born in what we would call an altricial state, like a loopy

26:12baby robin, where the bones are kind of spongy. They're not quite articulated. They're soft, indicating

26:18that they must have received parental care. And then also, of course, you know, if you have multiples

26:23of a species, you can look at the size and see whether that individual is old or young.

26:28X What's Good X asks, if the dinosaurs were annihilated by an asteroid, is there any evidence

26:35of the impact that's been discovered? Oh, yes. So the crater itself has been discovered. It's about

26:40110 miles across by 12 miles deep. It sits off the Yucatan Peninsula in the Gulf of Mexico. There's also

26:47an ejecta layer from the fallout from the asteroid strike that's been found all around the world.

26:52When that asteroid hit, it blew the equivalent of about Massachusetts times 12 miles deep into

26:59near-Earth orbit. And that material then rained down all over the planet. To date, very few fossils have

27:05been found in that layer. There's some fish scales in Belgium. There's a mosasaur vertebra and a tooth in

27:11Poland. There's some paddlefish and a dinosaur limb in North Dakota. They appear to have spring pollen

27:18trapped in their gill rakers. So we think the impact happened in the springtime. We think it came

27:22in from the Northeast at about 45 or 50 degrees. If you were on the Earth the day before the asteroid

27:29hit, you would have thought, well, this is how it's always going to be. These dinosaurs are always

27:33going to be on top. And then the next day, I think they were functionally extinct from a cosmic accident.

27:39It's just incredible. It gives me shivers and makes me thrilled about the fact that I became a

27:43paleontologist. That's it. That's all the questions. Hope you learned something. Until next time.

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