Smithsonian National Museum of Natural History

Webinar: Expert Is Online: Fossil Preparation with Myria Perez

Webinar: Expert Is Online: Fossil Preparation with Myria Perez
November 17, 2021

Amy Peterson:
Today, for this program, we're going to be talking all about how scientists prepare fossils for study and why that work is so important. We're also going to be using observation skills to compare animals that are alive today to fossil animals in order to learn more about those fossils. This program is part of our Celebration of Fossils series, where we're thinking about how animals of the cretaceous moved in water and through the air, so today's discussion is going to feature some of those cretaceous creatures. If you're interested in learning more about these animals, you can check out the rest of our programs in the Celebration of Fossils series, but more on that a little later. We're going to get started.

In that little description there, I used the word cretaceous a couple of times. I want to ask you guys, what's the first thing you think of when you hear the word cretaceous? Is there any particular animal or group of animals? Let's see. Go ahead and put those in the Q&A if you have any answers to that. Oh, James and Elise think of dinosaurs. So does Howard. That's classic. Ooh, Robert says Hell Creek Formation. Marcus thinks of a pterodactyl. That's awesome. Phil is doing a little word association. Crust and tectonic plates. Very interesting. Phoebe thinks of the T. Rex, which is a classic. Ms. Rathbun's class thinks of a period of time. That is correct. Cretaceous is a period of time. Oh, Cat's Meow thinks of crabs. Interesting. Kevin says, "An ancient animal was extinct awhile or million years ago." That's correct.

Robert Fonderson says Dinosaur National Park. Fantastic. Jet says archosaurs and my favorite avian dinosaurs. That's awesome. Let's see. We got another crabs. They are crustaceous. I like that. I like that a lot. Okay. Those are some awesome answers. Those are some great things that we think of when we hear the word cretaceous. So, now that we've thought a little bit about that, I would like to introduce Smithsonian's fossil preparator, Myria Perez. Hi, Myria.

Myria Perez:
Hi, everybody. Hi, Amy. I am coming from the National Museum of Natural History's Deep Time Fossil Lab in Washington, D.C.

Amy Peterson:
Awesome. Can you tell us a little bit about what you do at the Smithsonian?

Myria Perez:
Yes. I am a paleontologist, a fossil preparator, to be exact, so I spend my time with fossils that can be millions of years old and I work on them here in the Fossil Lab in the Deep Time Hall.

Amy Peterson:
Awesome. What got you interested in studying fossils and fossil preparation?

Myria Perez:
I have always been fascinated by fossils when I was a kid, and when I was 12, my mom took me to the local Houston Museum of Natural Science when I was growing up, and we went to our annual dino days, where I got to meet paleontologists, and I asked about volunteering. So, I started there volunteering as a junior volunteer, working on fossils and educating museum visitors, and even going on excavations. When it was time for me to look at school, I went to Southern Methodist University, where I earned my degrees in geology and anthropology while working on marine reptiles in between classes. I later did a research internship in D.C. at the National History Museum with Dr. Kay Behrensmeyer on another kind of marine reptile from Southern England, and then when I graduated college I started my first job in Dallas, Texas, working on animals like pachyrhinosaurus, and now I am the AAAS, Association for the Advancement of Science If/Then Ambassador promoting women in STEM and inspiring the next generation.

Amy Peterson:
That is fantastic. It's such an interesting story that you have. So, Myria, I've asked the audience what they think of when they hear the word cretaceous, and now I would like to know what you think, so what's one of the things that you think of when you hear the word cretaceous? And what do you think about some of the answers that we got from everybody?

Myria Perez:
I love that people said crustaceans in there. I think that's amazing. I also think about dinosaurs, but I really think a lot about mosasaurs, because they totally ruled the oceans during the cretaceous period. I'm even wearing my mosasaur hoodie today because I think of them all the time.

Amy Peterson:
That's awesome. What made you think about mosasaurs specifically?

Myria Perez:
I worked on mosasaurs in between classes when I was at Southern Methodist University, so I'm a little bit biased, and so a lot of those fossils actually are on display here in D.C. in an exhibit called Sea Monsters Unearthed, so I spent a lot of time on these animals in college, and a lot of them are from Angola, which is pretty cool.

Amy Peterson:
That's awesome. So, for those of us here that might not know, can you tell us what exactly is a mosasaur?

Myria Perez:
So, a mosasaur is a marine reptile that lived during the Mesozoic era, and here is a picture illustrated by Bob Walters and Tess, oh my gosh, I'm going to forget her last name.

Amy Peterson:
Kissinger.

Myria Perez:
Kissinger. Yes. And so, a lot of times they're mistaken for dinosaurs, but they're actually marine lizards that have adapted to rule the seas, and I like to think of them as kind of like lizard mermaids, but probably a little less friendly than a mermaid.

Amy Peterson:
This picture does a great job of showing them kind of mermaid-y, with the seaweed and everything. We use this image for supporting our school programs, as well, so I'm quite familiar with this piece. Okay, so they were marine animals, and they weren't dinosaurs. What does it mean to say that they were not dinosaurs? Can you talk about what the difference is?

Myria Perez:
Sure. I actually have a really cool diagram to show you. Here you go. So, this is a diagram called a cladogram. Usually it's depicted as an actual tree, similar to a family tree, with branches that connect moving backwards in time, but this bubble image gives you pretty much the same idea. The animals that are most closely related to each other will be in the bubble or in their own subgroup with a bigger one, so if you look at mosasaurs, they're in this group called lepidosaurs, which contains tuataras, snakes and lizards, and they breathe air, unlike fish, so they're not related to fish. And then if you look on the other side in archosaurs, you see dinosaurs, and pterosaurs, which are cousins to each other, and so the word dinosaur doesn't necessarily mean every fossil. It has a very specific definition. And mosasaurs are not dinosaurs. They were completely aquatic. And we can tell with these animals where they lived by looking at their fossils and where we find these fossils.

Amy Peterson:
Okay. That's really interesting. I didn't realize that mosasaurs were related to snakes and lizards. That's so cool. I'm really excited to learn more about these mosasaurs, but first, I'm curious about your work as a fossil preparator. So, let's talk a little more about what that means and why fossil preparation is so important. So, we all know what fossils look like when they're in museums, kind of like this. This is a Tylosaurus proriger. On display, they put all the bones in this beautiful pose, and their every single piece is in place, and they almost look like they're alive again. Do they look like this when they get excavated?

Myria Perez:
No. It actually takes a lot of work to prep them and make them look nice for display. When fossils are found, they're in sediment and rock, and we call that matrix, the fossil preparators do, and it's basically the rock around the fossil, and we have to remove this matrix to expose the fossil so we can study them and put them in our collections. And some of these are very fragile, of course, and fossil preparators may need glue or cradles to keep them from falling apart, or just have them cleaned really well before they go on display or be studied.

So, for example, here is a mosasaur called Prognathodon kianda, and on the left is what it looked like in the field. You can see the bones are embedded in the matrix or the rock. And then on the right, you have a reconstructed skeleton of that mosasaur, so you can see in between there's so much that goes on from field to museum, pretty much.

Amy Peterson:
That's so cool. Is that the same fossil in both pictures, just kind of before and after?

Myria Perez:
Yeah, so this one is actually in Sea Monsters Unearthed, and these are both casts and reconstructions of the same individual.

Amy Peterson:
That's awesome. I mean, it looks like putting together a jigsaw puzzle or something. Everything's all jumbled at first and we can take that and reconstruct these beautiful skeletons. So, fossil preparation helps us display these, but it also helps researchers too, right?

Myria Perez:
Absolutely. When we prepare fossils, we also conserve them for future generations to study and appreciate. We are always developing new methods to study fossils, from CT scans, to scanning electronic microscopes, to isotope sampling, so as technology continues to improve, we can learn new things about fossils and apply these new techniques discovered decades later after a fossil is found. So, we use tools to take high quality images of fossils to share with researchers that are all over the world, especially since some researchers may not be able to come to collections directly to study them.

Amy Peterson:
That's really interesting. You said new technology helps us improve in fossil preparation. How long has the Smithsonian been preparing fossils in addition to showing them on display for people to come and see?

Myria Perez:
The Smithsonian has had a fossil lab for about 100 years and this photo is the first vertebrate paleontology prep lab here at the museum. It started in the 1920s and while some of these techniques are pretty new, we actually use a lot of the same tools and techniques that were used back then to prepare the fossils. We use sharp tools, like picks, to chip away rock, and we use wood and steel mounts to put them together. That said, we've gotten a little bit more high tech in today's fossil lab. Here's a picture. Our current lab opened in 2019 with our new Hall of Fossils, the Deep Time, open to the public.

And our fossil is visible to the public, so I've got visitors actually looking into the lab as I speak, and we also have more prep space inside the collections which isn't open to the public, but we do a lot of work down there too.

Amy Peterson:
Awesome. What's the journey that a typical fossil would take from when it's found in the field to when it's done being prepped?

Myria Perez:
It's quite a long process, so once a fossil is found in the field, if it's a particularly heavy or fragile specimen, we create what's called a field jacket, which is made out of burlap, plaster, paper towels or toilet paper, depending on what you use for the separator to keep the plaster off the fossil. And once that field jacket is created, it cradles the bones. They're packed into crates and then transported here in the fossil lab, where we have plenty of light, and microscopes, and tools, where we can prep out the fossils very carefully.

And we start by removing these field jackets with saws, and of course, safety first. You got to wear your goggles and masks to keep all of that plaster from getting into your lungs. And then another very important thing we do when we open up the jacket is we document the fossils with photographs. And so, as we prep, we document them, and we use tools that I'm excited to share with you. Is that okay if I go ahead and share with you some of the tools that we use in the lab?

Amy Peterson:
Yeah. I'd love to see those. But before you show us, I'm curious what happens to those fossils once they're prepped, because I have a feeling that museums have more fossils than are just on display, right?

Myria Perez:
Gotcha. So, when something goes on display, usually not too many fossils go on display. Most of them go to collections. And I would love to show you an example of one that I just pulled out of collections to show you, so let's go ahead and-

Speaker 3:
Recording in progress.

Myria Perez:
Let's try this. I want to show you this mosasaur jaw.

Amy Peterson:
Oh, we're getting a little bit of an echo from you. Okay, so that's a mosasaur jaw that we're looking at right now. Myria, you're on mute.

Myria Perez:
So, this is a mosasaur jaw.

Amy Peterson:
Sorry. We're having an audio issue there Myria. I'm going to have to mute you on that camera. I'll just have to describe that a little bit, so that is a mosasaur jaw that Myria has told me is being rehoused in the fossil lab, and because these fossils need to be so carefully protected, they get put into new archival materials on occasion, especially if they were housed in things that we later learn are not quite so safe for the fossils. We'll use materials like foam to preserve them while they're stored in those collection drawers and sometimes they get fitted into a custom-fitted plaster jacket that holds the fossil perfectly and protects it from damage.

So, a lot of these fossils would crumble if they were handled directly, so having them in that cradle or that jacket helps researchers be able to look at them and manipulate them without actually directly touching the fossils. And that's one of the ways that fossil preparators keep these fossils safe so that they can be studied for as long as possible. And yeah, so a lot of these fossils end up in collections, but some of them do get to go on display.

Myria Perez:
Along with making rehousing cavity mounts, which is what you just saw there, some of the tools that we use, so I mentioned that fossils are very fragile, right? And we have glue, special reversible glues that help us piece back together fossils, or keep really, really crumbly fossils from becoming more crumbly. So, here's our glues. We've got a variety of different thicknesses. We got really thin to help us with the crumbly stuff, and then really thick if you have two pieces that break and you need to put them back together, and then, of course, you've got something in between if none of these are good for your project.

We also have brushes to brush away matrix and dust, so you can see what you're prepping. Very important to make sure when you are prepping your fossil that you're moving away that debris that you just created so you can see what you're doing. We've got pin vises, which are great for matrix or rock that's really soft, so you can go and gently remove that matrix. Then we also have, these are my favorite. I'll show you my favorite one last. We have air scribes and they are connected with a long hose that has pressurized air and this air vibrates this needle and it sounds like a dentist drill and it works like a mini jackhammer to remove very dense and difficult matrix.

Amy Peterson:
I was going to say it looks a little bit like a dentist's drill.

Myria Perez:
It sounds like one too, so we have to wear headphones and ear protection to keep that noise from damaging our ears. And then we also, I'll go ahead and show you this. This is when you have a really thick rock and a very big project. This is the mighty jack, which is great for when you have a lot of stuff that you need to remove and not a whole lot of bone. So, those are a few of our tools.

Amy Peterson:
That's so cool. So, what's your day to day like as a fossil preparator? What's the average day look like? What kind of things do you do?

Myria Perez:
It totally depends, so this fossil lab, our priority is research specimens, so if we have a curator that comes in and has a project, say they have some fossil leaves that they need prepped, then we go in and we take care of removing that matrix and making sure the fossil is healthy for generations to come. It could be plants, it could be micro fossils, it could be something really big. There is a dinosaur hip bone sitting next to me on the right. So, it really depends on what the needs are of the curators and collections. It can vary. And then, of course, we have volunteers that come in, so guiding them on certain projects, and outreach events like these.

Amy Peterson:
That's so cool. Okay. Now that we know a little bit more about fossil prep, I think we're going to take a few questions from our audience, so let's see. Ooh. Arian asks us, "Are the pieces displayed all from the same place or could it be that pieces from different places are put together?"

Myria Perez:
That's an excellent question. Sometimes it can totally vary. You can have what's called a composite specimen, where you have the same animal, but you have different individuals that are about the same size and those bones are put together and mounted. You could have a partial skeleton, where you have some real fossils and then some are casts, whether that's made from doing a molding and casting process, or even 3D printing now that that's become really big. And then, of course, you can have just a partial skeleton, so you only display part of the skeleton and nothing to fill in those gaps.

Amy Peterson:
Oh, so that's kind of why sometimes there's those lighter-colored patches on skeletons that you might see at a museum. It's kind of filled in.

Myria Perez:
Yeah. And sometimes, most of the time now that they're intentionally made to stand out a little bit, because if you're a researcher coming in to look at a fossil or a skeleton, and you're trying to measure bones, you got to make sure you're not measuring anything that's a cast or different from that individual. You want to be really specific.

Amy Peterson:
Very cool. Let's see. We've got a question from Granbury Middle School. If someone finds a fossil on their land, does the person make you pay or do they give it to you? That's a really good question. Knowing about who owns fossils when they're found is really interesting.

Myria Perez:
Yes. So, private land, whoever owns the land, that's where the fossil belongs. Public land, it can be difficult. You need to have permits, so any paleontologist that goes out and wants to look for fossils, they have to make sure they have proper permission and permits to go looking on certain land. That is a very good question and an important one, too.

Amy Peterson:
Interesting. We have a question. How do the fossils get from the field site into the museum? So, how exactly are they transported? Because I would imagine those things are pretty heavy in addition to being so fragile, too.

Myria Perez:
Yeah. Some of them, it depends on how remote the field is. So, if you're close to a city or you're nearby, maybe you're just transporting it in your car or in a vehicle from your institution. I know at past museums they've had to helicopter out the fossils because it was so far away from any road, so it really depends. And you have a team usually that helps you bring out fossils, especially large fossils.

Amy Peterson:
That is so cool. Okay. I think we're going to take just one more question now and then we're going to move on, so we have a question from... Let's see. We have a question. What do you do when a fossil breaks?

Myria Perez:
We use glue. It happens.

Amy Peterson:
It's what I do when I break something too.

Myria Perez:
We really try not to. You do everything that you can to make sure a fossil does not break, but it does happen. Some of them are very, very old and very fragile, so glue is our best friend. This glue is special. I don't think I mentioned it's reversible, so if you have a puzzle piece that you're trying to put back together and you find another one that fits, and it doesn't work because you just glued them together, you can actually use acetone, which is the same stuff in nail polish remover, to dissolve the glue, and then you can re-glue it. Yes. It does happen.

Amy Peterson:
That's so interesting. It's great that it's reversible because I bet that helps with being able to... If you make a mistake while you're gluing, you can just sort of unglue. But that's awesome. I think this is so interesting, all the stuff we've talked about with fossil prep. But now I actually want to circle back to what we started talking about with the mosasaurs. So, one of our big questions that we're exploring this week with our Celebration of Fossils is movement in extinct animals. So, how did mosasaurs move? We know they lived in water, so they must have swam, but do we know how they swam?

Myria Perez:
So, they moved side to side. If you've ever seen a lizard or a snake move, they move side to side.

Amy Peterson:
Yeah. Wiggling like that.

Myria Perez:
Yeah. And if you picture how a shark moves its tail when it swims, that's the kind of movement I'm talking about.

Amy Peterson:
Okay, so they swim kind of like sharks, but I don't think they're related to sharks. They weren't on that picture we saw before, right?

Myria Perez:
No. Even though they live in the same place, the ocean, they evolved from different ancestors, and sharks are from a group of cartilaginous fishes, meaning they don't have bones, they have cartilage for their skeleton. So, if you touch your ears and your nose, you kind can kind of wiggle it around. That's what their bones are made out of. So, they're very distantly related to reptiles evolutionary speaking, and it's called convergent evolution. So, when something is not related to another animal and they develop similar features and things, so think of the tail and how it moves, it's called convergent evolution.

Amy Peterson:
Okay, so that makes sense, so they swim in a similar way even though they're not related because they're living in the same place.

Myria Perez:
Exactly.

Amy Peterson:
I can see in this picture of the Tylosaurus, they have that really long tail, but I can also see they have flippers. They've got two little pairs of flippers there. How did those move? What did those do?

Myria Perez:
Yeah. You an see their flipper is made of all these little tiny bones which are called phalanges, and that make up the flipper, so these flippers would probably help it steer, and most of the propulsion, most of the moving forward and moving through the water would be from that side-to-side motion and tail.

Amy Peterson:
Okay. Interesting. I know that there are some animals that are really fast swimmers and others that are not as fast. Do we have any idea which mosasaurs would be, how fast they could have swam?

Myria Perez:
We don't know how fast they could swim exactly, but we do know that some mosasaurs were pretty agile in the water because of inner ears and how their structure looks inside. We know that some inner ears of an animal have a specific shape and we can tell that this animal was moving, probably darting around, and maybe avoiding predators or eating fast prey, and there's not... There's a lot of stuff we still don't know about these animals, but we are continuously studying them.

Amy Peterson:
Wait, so you can use the ears to learn about how they swam. How does that work?

Myria Perez:
Isn't that crazy? So, like if you spin in circles really fast, you probably get dizzy, right? And so, that dizziness comes from the inner ear, which has fluid in it that helps you figure out balance. So, if you spin really around fast, or you spin up and down, you could get sea sick like if you're on a boat that's moving and rocking around that fluid a lot, and so by looking at the structure of an inner ear, so for instance this is a ptychodon, a kind of mosasaur, and its brain case, and part of this project was to CT scan the brain case and inside you have the cavities or the leftover cavity of this organ, this inner ear structure. And so, we can scan that organ and segment it out into a 3D model and study it.

So, this ptychodon, but looking at this inner ear structure, it was found to be less susceptible to sea sickness, which is pretty cool.

Amy Peterson:
That's awesome. And you said that that's also part of fossil preparation, so for the CT scanning, you didn't even have to touch the fossil and you were just using computers and stuff, and it's still preparing fossils. That's really interesting.

Myria Perez:
Virtual prep.

Amy Peterson:
That's awesome. Okay, so based on its inner ear we think that ptychodon was agile in the water. Do we know why it would need to be so agile?

Myria Perez:
Well, probably for the food that maybe it was chasing, or maybe to avoid predators, but since we don't have the menus or shopping lists of ptychodon, we just have to compare them to living animals today to see what behavior was like and maybe what it ate. And so, yeah, here's its skull. This is the same animal that the brain case and the semicircular canal, so this guy had a very long, pointed snout, and you can see those teeth are really sharp and they hook back. Also, the nostril are on the top of its head so it could come up for air and surface before diving back under water, because remember, mosasaurs are related to snakes and lizards and not fish, so they need to breathe air.

And so, by looking at ptychodon's skull, I want to ask a poll question. Based on the traits we just looked at in this ptychodon skull, what do you think it most resembles of an animal today?

Amy Peterson:
Okay, so this poll should be popping up on our screens right now, and I want everyone to vote on which animal they think most resembles the ptychodon. And think about the animals' activities in the water, their habitats in the water or land, and things like that as you make those comparisons. Let's see. Ooh, it's neck and neck between lizard and dolphin. This is getting interesting. So far, nobody thinks elephant or fish. Very exciting. Okay. Still coming in. Still pretty close. Dolphin is a little bit ahead. We're getting there. So, Myria, when you see all these animals, do you have a favorite? It's probably the ptychodon, right?

Myria Perez:
Of course, it's the ptychodon. It's extinct. I think it's fascinating.

Amy Peterson:
It definitely is, but as I'm thinking about what it would have been like in the water, I think that if they were still around I would probably not go swimming in the ocean very much.

Myria Perez:
They're very cool. They also have teeth on the roof of their mouth, which is kind of cool. I can talk... Yeah.

Amy Peterson:
Oh, my goodness. That's crazy.

Myria Perez:
[inaudible 00:29:35]

Amy Peterson:
Okay. I'm going to leave this poll for another five seconds or so, so everyone put in your last bets. Let's see. Five, four, three, two, one. Okay, so most of you, about 60% said the dolphin is the most similar looking to the ptychodon, and you would be correct. So, we're going to walk through a couple of specific features that make us think that the ptychodon has similar anatomy, so the shapes of its features of its body, to the dolphin, because that's interesting. A lot of people said lizard, which is the closer relative to the ptychodon, but they're doing very different things. So, Myria, can you tell us a little bit about why people compare ptychodon to dolphins?

Myria Perez:
Yes. And I do want to say that those who voted lizard, I think that's also kind of right, because they are relative, related to them. But for we're looking at environmentally, what are these animals doing to their environment? How are they living? How are they behaving? Probably most similar to the dolphin because they are adapted for moving through the water pretty quickly, maybe grabbing and eating and catching fast prey like a dolphin. They're surfacing-

Amy Peterson:
They both breathe through the nostrils up at the top of the head, right?

Myria Perez:
Yeah. They breathe air, so they're coming up and surfacing. It's very dolphin like. So, again, these are things that show us convergent evolution. These two animals, you have a mammal and you have something that's related to lizards and snakes, that come from different ancestors, but they're tackling the same issue, which is living in the water. And they're doing very similar roles in their environment.

Amy Peterson:
Yeah. I can see they have the same long, pointy snout.

Myria Perez:
Yes. Long, pointed snouts. You got those sharp curved teeth to hold onto fast prey so they don't slip out of their mouth when they catch them.

Amy Peterson:
That makes sense because if the ptychodon has to be... We think it's really agile. That makes sense that it would go after really fast fishes and be able to catch them the way that we see that a dolphin catches them.

Myria Perez:
Yes.

Amy Peterson:
When we look at the skull and the teeth of an animal that's extinct and we compare them to living animals, we can figure out what things like ptychodon would have eaten. Is studying the teeth the only way to learn about what a fossil animal ate?

Myria Perez:
No, and this part is actually really exciting. So, other than teeth, sometimes you get fossils that contain stomach contents, and here is a picture of tylosaurus from the Deep Time hall and it has stomach contents. Another thing that you can see is bite marks, so the ammonite that it's chasing actually has bite marks from a tylosaurus, but going back to the stomach contents, if you have something in the abdomen region that has evidence of stomach acid etching, so it's you know for a fact this is something that the animal ate, you can prove the diet of these animals. And in this specimen in particular, it has the bones of a plesiosaur inside, and then to make things even more exciting, the plesiosaur has stomach contents too. It's like a big cretaceous sea turducken. You have meals and meals inside and you have direct evidence of these animals eating.

Amy Peterson:
Wow. How do you know that the other bones that were not the plesiosaur weren't just more stuff that the tylosaur ate?

Myria Perez:
They were found in the region for the plesiosaur and they were also etched away.

Amy Peterson:
Oh, so the plesiosaur bones didn't have as much stomach acid damage as the other ones did.

Myria Perez:
I think the plesiosaur does have some-

Amy Peterson:
It does have some but it's not as much as those other bones. That's how we know the plesiosaur ate that one?

Myria Perez:
Yes.

Amy Peterson:
Gotcha. Cool. So, I can also see this tylosaur, despite having a full stomach, is looking at that ammonite that's in the case there. So, do we think tylosaurs would have eaten ammonites, too?

Myria Perez:
Yes. So, their teeth mark's on the ammonite, so we do have evidence of them eating ammonites. So, they were eating a lot of stuff. Mosasaurs are kind of the T. rex's of the sea. They were totally taking over the oceans and they were the top of the food chain in most of their species, so they are pretty cool animals eating whatever they want.

Amy Peterson:
With teeth like that, it doesn't seem like there's much that would stop them. So, looking at the teeth, the shapes of the teeth, as well as if we get really lucky other kinds of evidence like these ammonite shells or stomach contents would help us figure out what mosasaurs ate. So far, we've mostly been looking at mosasaurs that have really sharp, pointy teeth. Did all of the mosasaurs have teeth that looked like ptychodons and tylosaurs?

Myria Perez:
No. There's actually a really, really cool mosasaur called Globidens that has rounded teeth. They look like mushrooms.

Amy Peterson:
They really do.

Myria Perez:
And so that, what you're looking at is those dark outer layers are the enamel part of the teeth, and in some of them you can actually see some wear that has gone on those teeth from this animal eating something that I'm not going to say, because I want to ask you guys what you think this animal was eating. It's got these round teeth, strong jaws, it's got some wear on the teeth. What do you guys think?

Amy Peterson:
Okay, so we're going to look at these thick jaws and these rounded teeth that get worn down, and we're going to think. We're going to hypothesize what they might have eaten. So, I'm going to launch our second poll, which should be appearing on the screen right now. Do we think that Globidens would have eaten kelp or seaweed, would they have eaten other fish, like the ptychodons and the tylosaurs did, would they eat nuts, or oysters? And so, we can think about how they're similar to other mosasaurs. We can think about how they're different. And we can think about what properties those teeth have that might make them better or worse at eating certain types of foods.

So, I can see that we've got a lot of votes in already. Oysters have definitely taken the lead. Most people think that they were eating oysters with those mushroom-shaped teeth. That's amazing. I've never seen any animals alive today that have teeth like that. I don't think there are any that have mushroom-shaped teeth today, are there?

Myria Perez:
I know that there are some coral crunching fish that have very rounded teeth. And I want to say parrotfish have them. They're all, they're in the dental battery, they've got just teeth, teeth, teeth, teeth all together in the little crushing fashion. This is making me hungry.

Amy Peterson:
I'm not sure Globidens would share with you, but maybe we can ask.

Myria Perez:
No. Probably doesn't want to share.

Amy Peterson:
No. Okay, I'm going to let this poll go for another five, 10 seconds. Oysters is still very much in the lead, but let's see if anyone else has any more votes to put in. Five, four, three, two, one. And our winner by a landslide is oysters. 75% of you guys think that these guys were eating oysters. Myria, were they right?

Myria Perez:
Yay. Although it probably would be a really fun nutcracker, Globidens at oysters, and we know this because there were a lot of these oysters called Inoceramus in this type of Globidens around, and then we also have evidence for this animal with stomach contents from South Dakota containing contents of oysters. So, they were going around and having a lovely seafood buffet.

Amy Peterson:
That's so cool.

Myria Perez:
Yeah. Lots of-

Amy Peterson:
We've actually got a question in here that I think fits off of that really well, so Globidens and ptychodons were eating different things, probably were in a little bit of different areas. Was there an ocean that was the best for being able to find mosasaurs? Do we know what kinds of oceans they would have lived in at the time?

Myria Perez:
Good question. Mosasaurs, they lived everywhere. We have mosasaurs from the Midwest in the United States. We have them in Russia, and China, and Antarctica. They were all over the place. The ones that we've been talking about, such as the ptychodon and the prognathodon, so the one where it's in the rock and then the reconstructed skeleton next to it, those were open water mosasaurs. A lot of them were open water mosasaurs, swimming in big, vast oceans. But they were pretty good at adapting to a lot of different marine ecosystems.

Amy Peterson:
That's awesome. We have another question from Sara. Do we know if mosasaurs lived in social groups, kind of like how dolphins do?

Myria Perez:
We don't know for sure. That would be so interesting to find out, but behavior is very hard to study with fossils since they're... You jut have the bones and the trace fossils leftover. But it would be cool to think about a pod of Globidens hunting together or something, but we don't know, unfortunately.

Amy Peterson:
Yeah. Since that is one of those questions we're not sure about, that brings me to my other question, which I guess you've answered a little bit. We don't know everything there is to know about mosasaurs. Are there still areas where new discoveries help us learn different interesting things about them?

Myria Perez:
Yes. Science is constantly learning things. Paleontology, we're constantly finding new fossils. We're even looking at fossils that we've discovered before and looking at them closer with new technology, so like remember when we were talking about fossil prep, and conserving them for a while, because we don't know if a fancy new microscope comes to us that has all these capabilities. So, for instance, in 2013, there was a mosasaur that had been looked at before, and somebody went back in and looked at the specimen, saw that there was soft tissue preservation on it, and decided that it needed to be prepped more so we could maybe see what else was going on. And with this, they found a soft tissue tail fluke, so this little... almost looks like a shark tail, right? You got the upper part and the lower part.

And they found evidence for mosasaurs having these, which is really cool. So, prep, with prep, you're able to make more discoveries in this case.

Amy Peterson:
I didn't even know you could have fossil soft tissue. That's amazing. And so, they didn't know for sure what the shape of the end of the mosasaur's tail would have been like, right? Because the bones were there in that long, curvy tail, but they didn't know what the rest of the soft tissue would have looked like until they found this.

Myria Perez:
Scientists have speculated that maybe the tail had dipped down, but we had no direct... We didn't have enough evidence for that. But with the soft tissue and with this prep that just happened, they were able to say yes, this animal does have a tail fluke. It looks just like and probably moved like a shark in the open ocean.

Amy Peterson:
That's so cool. So, not only is that a great story of how we're learning new things about mosasaurs all the time, as well as all the other fossil creatures, but it also tells us how important it is to have a really skilled team of fossil preparators that are working on all of these things. That's so cool. Thank you for sharing all of that with us Myria, and at this point, we're going to open to some more audience questions. First up, we have a question. How large is the largest mosasaur ever found?

Myria Perez:
That would be Mosasaurus hoffmannii. I hope I'm saying the species name right. But it is about 56 feet long. That is a huge animal.

Amy Peterson:
That's longer than a school bus. That's huge.

Myria Perez:
It's [inaudible 00:42:28].

Amy Peterson:
Oh my goodness. Definitely I'm going to stick with what I said before. I'm really glad that I don't have to share the ocean with mosasaurs. As cool as they are. Okay. The Didders and Ms. Rathbun's class both ask how many different types of mosasaurs existed?

Myria Perez:
More than 100 species have been found and that can still go up.

Amy Peterson:
100 different species, so those are probably from different time periods, and places, and things like that.

Myria Perez:
Throughout the Cretaceous. The Cretaceous period is divided into different times within that, and so they just took off in the Cretaceous period. They just diversified. There were so many species that happened, so many different sizes, and they ate different things, as well. They're quite cool.

Amy Peterson:
Awesome. Now, Kat would like to know why are those rounded teeth best for eating oysters? I would have thought pointy teeth would be better to crush into those shells.

Myria Perez:
Great question. So, with sharp teeth, and actually we can compare it a little bit to if we want to talk about T. rex a little bit. So, T. rex has really big teeth, and they're not actually that sharp, and they're used for crushing bone. If you look at a crocodile, you see they do look sharp, but they're very strong, and they help crush the bone. So, when you have something that's really round and kind of bulky, like really thick, you're able to crush things easier. If you have really sharp teeth, so if ptychodon were to go and try to eat an oyster, those teeth probably would break and it wouldn't be strong enough.

Amy Peterson:
Because they're so skinny, they're more brittle. So, if you crunch really hard on something really, really firm, you run into that issue of possibly breaking a tooth. Okay. Also, I know that reptiles today, including crocodiles, they can't really chew moving side to side at all, like we can move our jaws side to side, but they really only snap together like a vice. Would that maybe have been true of the mosasaurs too, so they need a big, flat, crush surface to be able to crack that fossil, or crack that shell?

Myria Perez:
I'd have to get back to you on that. Since they are related to snakes and lizards, I'd have to look up how their jaw works, if it's similar to maybe snakes, where they can dislocate it a little bit. I'm not completely sure, so I'm going to say I don't know.

Amy Peterson:
Okay. That's awesome. Let's see. Fin would like to know were all mosasaurs hunters?

Myria Perez:
I believe so. I don't think there has been any herbivorous mosasaurs found yet, but maybe that'll change.

Amy Peterson:
So, probably no vegetarians.

Myria Perez:
We'll have to see. Yeah.

Amy Peterson:
Okay. Phil would like to know because mosasaurs are marine reptiles, you only find them on current coastlines, right?

Myria Perez:
You can actually find them in the middle of Kansas. So, during the Cretaceous period, Earth looked very different. Our continents looked very different. For example, picture the United States. In the middle of the United States, there was a western interior seaway where it was ocean, so like in parts of Texas, and Kansas, and Oklahoma, were under water during the Cretaceous, so you're having mosasaurs live and die and fossilize, and now we can see ocean fossils. That's why you can get shells and fossils that are marine in a terrestrial, a land environment today, so it looked very different.

Amy Peterson:
Oh. Yeah. I remember you said that there were some that were found in Angola, too. And Angola's not under water now, but I guess it used to be. That's really interesting. Okay. Let's see. Molly would like to know what is the oldest mosasaur found.

Myria Perez:
The oldest. I don't know. I do know that there is a very small mosasaur that was pretty old and it had very similar teeth to Globidens, very crushing teeth, but it was small. It was only 11 feet long. Which is still kind of big.

Amy Peterson:
Only 11 feet long. Puny. Okay. We've asked a lot of questions about mosasaurs. I think we're going to pivot back to some of those fossil prep questions from earlier. Abidair would like to know are there special stands that you use to work on every single dinosaur?

Myria Perez:
Oh, special stands. I guess for mounting the animals it really depends on the size, how heavy certain fossils are, so some fossils, each fossil has its own personality pretty much, and that goes for when you're fossil prepping it, too. Some fossils can be really durable and you just need a little bit to help them stand up, or you need a little bit of glue. Some fossils are super fragile and you got to make sure you have cushions around them, so it really depends on the specimen itself.

Amy Peterson:
Very cool. I think I remember you telling me there's something special about where you lay down those bones, like when you're making the jackets and casts. Something about the sandbox that you use. Could you tell us about that?

Myria Perez:
Yes. So, when we are getting ready to put a jacket or a protective case around a fossil, and it's in the lab, we use sandboxes, and we also use them for gluing things because with a sandbox, you're able to move around your fossil, because fossils are all different shapes and sizes, right? So, you got to be able to move them around and then balance fossil pieces as you're gluing them. And so, we use the sandbox to create jackets, as well, so if you have a really big fossil, you put it into the sandbox. You adjust it so the sand can make it however you want it. Then you create the jacket.

Amy Peterson:
Okay. And so, the sand, what kind of sand? Is it just sandbox sand?

Myria Perez:
No. Here, we use garnet sand, which is a really pretty red, and if I had... Let's see. Just turn my laptop a little bit. So, there's the sandbox, and then inside, I don't think you can see it, but it's red, and we use garnet sand, and this kind of sand does not kick up a lot of dust. If you've ever been a sandbox, it's kind of dusty, and we don't want to have more dust than we need here, so we use the garnet sand, which is really pretty. But there is where we create the jackets in this little sandbox here.

Amy Peterson:
Oh, wow. So, fossils and garnets all in one place. You have a very cool little office. Oh, Tim would like to know what was your first thing that you ever prepped out?

Myria Perez:
The first thing I prepped in the lab or in the field? In the field, I prepped out a eryops, and actually I think there's a... Oh, no. You can't see him. So, picture a really big frog salamander thing. Huge. Like great dane. Maybe not great dane size, but like rottweiler-sized amphibian. And I just got my first fossil was a shoulder bone of that, and I thought, "Oh, it's a rib." And then it just kept going and it turned into a shoulder bone, so that was my first field experience.

Amy Peterson:
That's so cool. Elizabeth has a really great question and this is one that I'm curious about, too. Sometimes the bones and the matrix look a lot alike. How can you tell which one is matrix and which one is bone?

Myria Perez:
Yes. It can be very tricky. You train your eyes. You look for color differences, so there can be a little bit of color difference. There's a texture difference, as well, so bones have sometimes these stripes almost, or these ridges, where muscles would attach. They have pits and different textures that the rock doesn't have. And then, so you have color, and then shape, so if you see something that's kind of curving that you recognize as, "Oh, that's a backbone," or, "Oh, this is a hip bone." The more you look at it, the more you can kind of tell them apart. It does take time.

Amy Peterson:
So, it's really just a lot of practice, but-

Myria Perez:
Lots of practice.

Amy Peterson:
... once you get good at it, you sort of develop the eye?

Myria Perez:
Absolutely.

Amy Peterson:
Okay. We have another really good question. What do you need to take in university to be able to work with fossils?

Myria Perez:
Good question. If you're wanting to study fossils, you'll want to do some sort of natural history, and art classes if you want to be a preparator too, using-

Amy Peterson:
Art classes, so not just the science?

Myria Perez:
Yeah. For prep, using your hand-eye coordination is very important. Drawing is very important. And then also natural sciences, so I got my degree in geology and anthropology, because a lot of times paleontology is not a major, but biology is great, anatomy is wonderful, chemistry is helpful. Any natural science, because paleo is a combination of so many different sciences and even art.

Amy Peterson:
Okay, so if we follow that kind of trajectory of looking at lots of different natural sciences in college, that's one way that we can approach becoming a fossil preparator, so in case this webinar has inspired any future fossil preparators out there, now you know the pathway. I think that it's a really interesting career path, Myria, that you've found for yourself, and more people should know about it, because I think there's a lot more work that we can be doing in fossil prep.

So, Myria, on that note, overall, what sorts of things do you think the audience should walk away from this webinar? What's your take home message for everybody?

Myria Perez:
Be curious and check out your local museum. If you're nearby, come check out the Smithsonian Natural History Museum. Come wave at us in the fossil lab so you can see all the new projects that we're doing. And it's constantly changing, so I think that's it.

Amy Peterson:
So, be curious. Should we be looking for fossils everywhere?

Myria Perez:
Well, not everywhere. Be careful when you look for fossils. Definitely go look for them at a museum, though.

Amy Peterson:
That's fair. Okay. Thank you so much, Myria. This was really awesome. Thank you to everybody that was able to join us today. We hope you've enjoyed the webinar. And if you liked this, don't forget to check out the rest of the events in our Celebration of Fossils series. It should be appearing on the screen right now. Tomorrow, we have a Smithsonian Science How webinar with Dr. Matthew Carrano, and on Sunday we have a bilingual program called Bailando a traves del tiempo - Quetzalcoatlus, where we'll be thinking about how the giant pterosaur called Quetzalcoatlus would have moved, both through looking at fossil evidence and by moving our bodies. Both of these programs will also be interpreted in ASL and closed captions will be available for both, so be sure to check out the website for more information on those, and also check out the website for some of our recorded webinars. They're all available about a week after the live event has occurred, so all of that content is available for you guys to explore and learn a little more.

Thank you so much. And thank you, Myria, for being here.

Myria Perez:
Thank you.

Archived Webinar

This Zoom webinar featuring fossil preparator Myria Perez aired November 17, 2021, as part of the "2021 Celebration of Fossils Virtual Event Series." Watch a recording in the player above.

Description

In this video fossil preparator Myria Perez shares how fossil preparation works and what we can learn about animals from their fossils. Plus, we explore some of the traits of the Mosasaurs, the marine reptiles that ruled the ocean in the late Cretaceous. 

Moderator: Amy Peterson, Museum Educator, Smithsonian National Museum of Natural History.

Related Resources

Resource Type
Videos and Webcasts
Grade Level
K-2, 3-5, 6-8, 9-12
Topics
Paleontology
Exhibit
David H. Koch Hall of Fossils - Deep Time