Please reload

How Paleo Pigments are Helping Scientists Color In the Fossil Record: Jakob Vinther on reconstructing color patterns in feathered dinosaurs

July 16, 2019

 

When Jakob Vinther looks through the lens of his electron microscope, he gets to glimpse at remnants of a time most of us can barely imagine. Although our curiosity, previously fueled by scientific inquiry constrained by the limitations of its time, had led us to make certain educated guesses about fossils recovered from the folds of the Earth, Vinther’s work is changing the field of paleontology by showing us what dinosaurs likely looked like, how they lived, and the dinosaur-eat-dinosaur world removed from us by 65 millions years of history and evolution.  

 

Vinther is a paleobiologist at the University of Bristol and the leading authority on pigmentation in dinosaurs. His fascination with nature and interest in biology, which extends to prehistoric life forms, was sparked — at least in part — by his youth. “My mom had always collected shells on the beach, and my aunt as well,” shares Vinther. Going away to summer camp when Vinther was 11-years-old was also a pivotal experience. After finding a number of fossils on a trip, the young biologist began to read up on a field of scientific investigation he would one day disrupt. 

 

His work, however, does a lot more than simply provide color scheme parameters for people who love depicting dinosaurs, although it does that too. Restoring dinosaurs in living color and figuring out their color patterns illuminates how the birds of today came to be the way they are. In other words, his work has opened the door for other scientists looking to explore the spectacular depths of evolution and biology. And bridging the gap between the dawn of the dinosaurs and the dawn of humanity, and the worlds in which they lived, is no small task. 

 

Of course, there are doors that still need to be opened. We haven’t placed color on all dinosaurs; nor have we figured out all of the colors the dinosaurs could be. But where there are inquisitive minds, researched hypotheses, and unanswered questions, we find the people who are willing to do the work.

 

ARTpublika Magazine spoke to Jakob Vinther about dinosaurs, prehistoric pigments, and the incredible questions being explored in paleontology today. 

 

 

How did you grow up? 

 

I was born and raised in Denmark, but I am half Icelandic. I spent quite a bit of time in Iceland as a child, where I got interested in plants, animals, and rocks. As I grew up, I developed an interest in past life, and therefore chose to become paleontologist. 

 

Did you have a favorite animal or dinosaur that sparked this interest?

 

Not really. I think for many people, who have an interest in paleontology, it’s usually because of dinosaurs. I spent most of my time outside, catching newts, salamanders, and frogs. I had an aquarium [where I kept] turtles and lizards, and I had a conservatory where I grew all sorts of carnivorous plants. I’ve always had a generally big interest in nature. I don’t have favorite class of dinosaur. I don’t really tend to have favorites.

 

 

I started collecting fossils when I was a child — of things like sea urchins and belemnites. Specific kinds of conditions give rise to really well-preserved fossils. I realized that if you know where to look, there are vast amounts of stuff that can actually be found and studied. This sparked my interest very early on. In Denmark you can collect fossils from 500 million years ago, which is really fascinating. 

 

When you say, “certain conditions” are necessary, what are they?

 

Anything that dies becomes recycled, because organisms — like worms, scavengers, bacteria, and fungi —  will break down all organic tissue. We see that when we look for sites where an animal was buried really fast and there were very low levels of oxygen, we suddenly find these very, very spectacular things. The black sea is a very good example, because it has really noxious waters and the oxygen gets starved out. 

 

Can you give a few examples? 

 

 

A classic example is this amazing fossil from Bavaria in Germany called Archaeopteryx, which is a dinosaur-like bird. It was discovered not long after Charles Darwin (1909 — 1982) published his book, On the Origin of Species (1859). This fossil is a complete skeleton with feathers associated to it. Feathers, of course, are organic structures; generally, they would not preserve. 

 

This discovery helped us confirm that birds had ancestors that looked very different from how they look today, and that we can trace them back to dinosaurs. In fact, birds are dinosaurs — birds have evolved from within dinosaurs. You cannot really distinguish between them because they are the same thing — birds are only dinosaurs that have survived until today. Then, we also found feathered dinosaurs in China. 

 

We have been able to reconstruct how birds came to be the way they are, and how feathers have evolved before birds were able to fly with them. When we see feathers, we think about flight, but feathers are actually for insulation; as warm blooded animals they have to conserve their precious heat. They are also for making displays; birds use feathers to communicate with each other and to camouflage themselves. 

 

By looking at these fossils and figuring out how feathers are assembled and so on and so forth, we have discovered pigments preserved in these feathers. Of course, we then started to probe when they became colorful. 

 

Do you have any clues as to when in history that happened?

 

 

If you think about the classic scene in Jurassic Park (1993), when all these velociraptors are chasing the kids around the kitchen, those dinosaurs were actually covered in feathers. They are quite close relatives of birds, among what we generally appreciate as dinosaurs within the theropods. And we have found relatives of these dinosaurs, which had really bright iridescents — like the bright colors you see in peacock feathers today. They resemble that, and we found that it goes back to 155 million years ago. 

 

Wow! 

 

 

Yeah! And another dinosaur (Anchiornis, discovered in 2009), one of the first ones we ever looked at, kind of looks like something between a chicken and a woodpecker. It has a gray body and long feathers on the forelimbs and hindlimbs — white with black spots, with sort of a spangled pattern. Interestingly, on its head it has a patch of reddish feathers that are really different from the rest of the body. That again suggests signaling, it has a patch that sort of fans out; it could have been used for sexual selection or species recognition, so that specific color patterns could then be used to communicate within the species. 

 

So, the discovery of fossil pigments has helped us start to paint a picture of what dinosaurs looked like and, in some respects, how birds came to be and evolved. It helps us understand when certain traits in birds first appeared. For example, modern birds make nests, lay their eggs, and then sit on top of the nests and keep the eggs warm. Sometimes they get scared away. It then [becomes] advantageous for the eggs to be camouflaged — for them to be less visible. So, then, extremely colorful eggs evolved. 

 

Some of the most beautiful eggs are made by guillemots, which are these sea birds. They are so extraordinarily colorful —  blue and green, with spotted patterns and irregular lines that almost look like Japanese Calligraphy littered across the surface. The interesting things is that a colleague of mine — a PhD student at Yale, her name is Jasmina Wiemann — was looking at dinosaur eggshells and found pigments of green, blue, and brown colors. We can see they made nests that look similar to the nests of modern birds, and we have even found dinosaurs still sitting on tops of the nests. Therefore, we can also trace back the evolution of colorful eggs to their origin.  

 

Are fossils of bones helpful for your investigations? 

 

Sometimes a little bit of organic material gets preserved in the bones. But, it’s highly controversial. We recently published a paper where we demonstrated that bones are full of bacteria. Turns out, when we find fossil dinosaur bones, they are actually full of bacteria that seeped into the bones underground and used the nutrients that were available in there. The problem is that some people have found proteins and even DNA inside dinosaur bones and thought it was from the dinosaur, but we’re highlighting that there may be a lot of issues with this idea, because proteins and DNA are highly unstable. 

 

Generally, we don’t find any of those molecules on the archaeological record more than a million years back, and dinosaurs are obviously more than 66 million years old. While some organic material inside these bones may survive, but there are no pigments inside bones. 

 

So, when we have the extraordinary conditions that I mentioned earlier — when an animal with its organic tissue gets buried really fast in low oxygen environments — what we see is that the pigments survive because the pigment molecules are really stable. Therefore, when we look at a dinosaur fossil with feathers, we can see the color patterns with the naked eye and its really cool. So, when I started thinking about these things more than 10 years ago, I looked at some previously discovered dinosaurs and, indeed, you can see stripy patterns, and things like that, preserved in their feathers. That’s basically how we do it.  

 

Down on the south coast of England, close to where I live, people have found fossils of marine reptiles. Back in the Victorian day, Elizabeth Philpot (1780 — 1857) and Mary Anning (1799 — 1847), who were celebrated paleontologists, excavated these fossilized marine lizards and sold them off to aristocrats and natural history museums that were just emerging. Many of the letters that they sent out describing the fossils they had for sale were actually written using fossilized ink. The ancestors of squid and octopus were found in the same deposits as the marine reptiles. Their ink sacks were preserved with the ink inside, so the paleontologists took it out, dissolved it in water, and then used it to write those letters, just like people have been doing for millennia. 

 

 

We have these letters and I went to see one. It’s a 200 year old letter written with 200 million year old ink. So, people have known for centuries that melanin gets preserve in the fossil record, because of things like that. But, for some reason, people haven’t really thought about the preservation of melanin in big fossils, like dinosaurs, probably because there wasn’t a lot of soft tissue found in dinosaurs until very recently. But then this vast treasure trove of dinosaurs out of China changed that, but people still haven’t thought about melanin or how well it may be preserved in dinosaurs until I was sort of thinking about it as a PhD student. 

 

So, my PhD was actually about a completely different subject, but as a side project, I was looking at these ink sacks, trying to understand why something that’s fluid in life becomes such a hard lump that we find in the fossils. While I miserably failed at understanding why that is, I was looking at some of these fossilized relatives of cephalopods (squid and octopus) that we had, with this preserved ink, under a high powered electron microscope. I realized that the ink was comprised of these beautiful tiny balls that are about a micron in diameter. And when you look at ink from a squid today, it looks exactly the same; therefore, you could identify this ink by the structure of the pigment granules that they’re forming.

 

I was looking at different fossils from different time periods and countries that had preserved ink. Ink is composed of melanin, which is the pigment that gives color to our skin and hair. I started thinking that if it preserves well, then it must be all over the place. Our melanin is contained in little organelles — little factories where the melanin is produced within certain cells, which are called melanosomes and have distinct shapes. In red hair, the melanosomes are shaped like little balls; in brown hair, they are shaped like little sausages. So I thought, OK, I’m going to take some fossil feathers [and put them under the microscope] and my search image is going to show little sausages. Indeed it did. 

 

As I zoomed in on the specimen, I was met by this ocean of little sausage-shaped objects, so it fit my scientific predictions. And that’s sort of how everything started, and then we started looking at various feather patterns. The cool thing is that when you see iridescent birds with these metallic colors — those are structural colors, where there’s an interference between different materials in the feather that create a sort of a nanostructure. And melanosomes are involved in making that nanostructure. Since we could see that these melanosomes are organized within this structure, we were thinking that maybe we can find these nanostructures preserved. 

 

So, just a year after we declared our first discovery — fossil melanin in the feathers — we were able to show that a one-hundred-million-year-old feather was actually iridescent and had metallic sheens. Soon after that, we put colors on a dinosaur, and that was the dinosaur with the reddish headdress. A couple of years later, we also found a dinosaur that had been iridescent, but the way we did that was not by finding the original arrangement of the melanosomes, because we did not have that preserved; what we discovered was that the shape of the melanosome could tell us if it was iridescent. A black melanosome is shaped like a sausage, but an iridescent melanosome is a lot skinnier. 

 

We can also detect the color grey, because birds make grey feathers in a very distinct way. When people get white hairs, it’s usually because we get white hair mixed in with darker hair. But birds make these saturated gray colors, like pigeons. Turns out the melanosomes have a distinct shape in order to make that gray color, too. This means we can detect and predict colors by simply looking at the shapes of the melanosomes. 

 

How did you initially get to test your hypothesis? Isn’t it hard to get fossils you can use? 

 

Back then, I was this lowly PhD student that no one knew of, so I kind of predicted that no one was going to give me permission to scrape material off of their precious fossils. In Denmark, we have a locality where we can find complete fish and insects preserved with their color patterns, and we can also find birds preserved with feathers. So, I thought this would be a brilliant place to start my quest. I found the beautiful little head of a bird, where it was just the neck and the skull with this halo of feathers surrounding it. l thought that the specimen was small enough to get under a microscope, and that was the first thing that I looked at. That was in 2008. 

 

 

I localized where the feathers were. The thing is, in an electron microscope, you don’t see colors like you would normally. Because you are making an image with electrons bouncing off the surface, its like looking at the lunar landscape with no color. But, I found where I thought the colors would be and started to turn the dial. After zooming in and zooming in, this amazing image of lines and objects just veered into view. When I was looking at it, I thought, What if you could find melanin preserved in dinosaurs? What could that lead to? Now, we have put all these different colors on dinosaurs and can say all these things about it. 

 

Did you make any surprising discoveries for yourself? Is there anything that stands out to you about your work? 

 

After discovering the pigments, we then made advances with a number of collaborators who offered all kinds of interesting ideas. Together, we were able to find methods of predicting colors in a sort of statistical way, by looking at living birds and measuring the melanosomes in their feathers and then looking at fossils and their melanosome shapes; from there, we can predict how their colors and hues may change due to fossilization, because the pigments undergo a chemical change. A colleague also started looking at iridescent colors and showed how we can predict them based on the shapes of the melanosomes. 

 

You always wonder about how far you can push this. People have pointed out that there are limitations to putting colors on the past, because there is lots of information that we have lost, and the ways we predict colors right now are still quite crude. We cannot tell the different colors of iridescents, and we cannot tell apart different shades of black, brown, and gray. But, compared to what we thought was possible before, this is pretty amazing. 

 

So, going back to the question. We’ve been thinking about [what we could learn] from fossil color patterns. I have a colleague, Innes Cuthill, and he and his group are working on camouflage — doing all kinds of tests trying to look into how it functions. One of the things that they have been looking at is countershading. Countershading is when you have a lighter underside and a darker upper surface, and that’s a very conspicuous color pattern. 

 

So, if you think about squirrels, or foxes, or penguins — they have a light underbelly and a dark surface. That’s actually a camouflage pattern, and the way it works is quite interesting, because our brains use various types of cues to identify an object. Shape detection and shading cues are really, really important for identifying objects and their three dimensionality. Disruptive camouflage is when an animal evolves patters that basically try to break up the patterns of their body to counter edge detection in predators that may be looking at eating the animal.

 

As you know, light varies depending on location. So, if you were going to make a painting of a person sitting in a sunny room, you would have diffused lighting, therefore the shading transitions would be gradual, because the light coming in would be soft. But, if the person was out in bright sunlight, then you would get sharp, contrasting transitions across the body. [From this,] you could predict that animals living in open environments, where there is more direct illumination from above, have sharper countershading that’s high on the body; and animals living in closed environments, like forests, would have gradual countershading low on the body. 

 

We were able to demonstrate that this was indeed the case. There is also some correlation [between color patterns] and latitude, because the changing angle of the sun and wether you are closer to the equator or at higher latitude. This means when we find countershading in a dinosaur, we can predict the environment that it lived in. And so we have done this with two different dinosaurs from China. 

 

 

One dinosaur (Psittacosaurus) we looked at was this tiny little plant eater about the size of a Labrador — really, really cute looking. It sort of looks like ET with a really wide head; it has a naked body with a type of bristles on its tail and patterns across the body. We can see that it had a reddish brown color based on the shapes of its melanosomes. We can also see that there is a distinct transition of where it becomes lighter on the belly. 

 

Artist Bob Nicholls reconstructed this dinosaur, which was possible because it was so small. He got all of the proportions right, like the size of its muscles, and even added some fatty tissue to try to get as detailed of a rendition of this animal as possible. By looking at the preserved color patterns of this really extraordinary specimen, we were able to project these color patterns on to a mold of this dinosaur and thereby could see where this transition was. 

 

He created another mold, which was painted gray. We tried to submit it to light to see how the shadows were cast on it, and then predicted what would be its optimal countershading in an open environment as well as a closed environment, to see which one matched the fossil. We were able to see that the closed environment was the one that matched the dinosaur, therefore this dinosaur likely lived in the forest. It evolved those color patterns because of predation; survival of the fittest is how evolution happens, and those who can’t adapt, disappear. We can reverse engineer the habitats that the dinosaur lived in based on its color patterns. 

 

 

Now, we found another dinosaur (Microraptor) in the same deposit as this dinosaur; he had a preserved lizard inside his belly. The feathers preserved on this dinosaur make it look like he’s got a striped tail and a bandit mask over his eyes. [When] birdwatching, the more you intently stare at a bird, the greater the chance it will fly away; it is deeply engrained in most animals to be worried if a pair of eyes is staring at them, because that might mean that they could get eaten. So, another thing with countershading is that it’s a reflection of wether you are the predator or being predated on.

 

Anyway, we reconstructed the counter shading of this dinosaur, too, and found that it lived in an open environment. What we found is that even though these two dinosaurs were discovered in the same lake deposit, they may have actually lived without ever interacting with each other, because they came from different environments near the lakes. Interestingly, if you take a mammal and domesticate it, like a horse or a cow, it will loose its countershading. 

 

So, if you let it free, would the countershading come back?

 

Yeah, it would have to. It would evolve back really fast.  

 

Is that why releasing a domesticated pig turns it wild, like a boar?

 

No, but it’s actually really interesting that you mention that. Wild boar are some of the few mammals that don’t have countershading and its because you don’t want to mess with a wild boar. Piglets, wild boar piglets, are countershaded because they are vulnerable. So this is a really good example to lead up to what I was going to move toward. Elephants are gray, right? They don’t have countershading. Same with rhinos; they don’t have countershading either. And if you take a moose, for example, it’s also not countershaded. That’s because you don’t want to mess with a moose. Predators today can’t attack an elephant or a moose or a rhino, so they’ve lost their evolutionary countershading because they don’t need it. 

 

 

Here’s the thing, a couple of years ago, we were been looking at a really big plant eating dinosaur that was discovered in Canada. This is a type of dinosaur called Borealopelta, and its sort of a power-like herbivore — big (1.3 tons), stocky, and covered in armor. They have massive spines across the body, and some of them even have a spiny club, or a blunt club, that they could use to swing around and break the skin of a tyrannosaur. We found pigments that were preserved, they were a brownish color, and we could see it was countershaded. 

 

So, it had predators? 

 

Yes! It had predators. And it means that back when it lived, it was really scary. So, with something like color patterns, we can even say something about how scary these dinosaurs were. 

 

Is there anything you’d like to mention that wasn’t addressed? 

 

There are lots of people who love dinosaurs, and love to depict dinosaurs. I was kind of worried that paleoartists would be disappointed that we found these colors, because that takes away some of their artistic freedom. But, I actually found it the other way. People embraced this information; it helps them think more about details and possibilities within the constraints that are now in place. 

 

Understandings of past colors and color patterns has made it really fun to see what some of these dinosaurs look like in the versions artists have made of them. And it’s really stimulating, because while working with the artists, they’ll ask me questions about wether or not a dinosaur did this or that, and their questions are the types that I don’t normally think about. So the synergy between artist and scientists is something I thrive on, and it’s something I would like to explore more of in the future. 

 

 

Note* Image Credits: 1. Mosaic evolution in an asymmetrically feathered troodontid dinosaur with transitional features via Xing Xu, Philip Currie, Michael Pittman, Lida Xing, Qingjin Meng, Junchang Lü, Dongyu Hu & Congyu Yu Source: Mosaic evolution in an asymmetrically feathered troodontid dinosaur with transitional features, Nature Communications 8, Article number: 14972 Wiki CC BY 4.0 | 2. Jakob Vinther sourced from University of Bristol |3. Fossil of Passaloteuthis Bisulcata at the Urwelt Museum Hauff Holzmaden | Credit Ghedoghedo via Wiki CC BY-SA 3.0 | 4. Restoration of Archaeopteryx chasing a juvenile Compsognathus, Credit Durbed via http://durbed.deviantart.com/art/Archaeopteryx-litographica-313930947 Wiki CC BY-SA 3.0 | 4. Illustration of the basal troodontid Anchiornis huxleyi. Colors based on the patterns recovered by Li et al. 2010, Credit Matt Martyniuk via Wiki CC BY 3.0 | 6. Common Guillemot (Uria aalge) Eggs via Wiki Public Domain | 7. Autograph letter concerning the discovery of plesiosaurus, from Mary Anning; sketch of plesiosaurus | Wellcome Collection.  

https://wellcomeimages.org/indexplus/image/L0022370.html CC BY 4.0 | 8. Squirrel via Wiki Public Domain | 9. Model of Psittacosaurus Based on Skin and Pigmentation Patterns on SMF R 4970 Left lateral view (A), posterior view (B), right lateral view (C), and anterior view (D),  Robert Nicholls via 3D Camouflage in an Ornithischian Dinosaur, Current Biology (2016), https://dx.doi.org/10.1016/j.cub.2016.06.065 Wiki CC BY 4.0 | 10. A pair of the microraptorine Microraptor searching the forest of Liaoning in spring. by Durbed http://durbed.deviantart.com/art/Four-winged-thieves-341517949 via Wiki CC BY-SA 3.0 | 11. Single dorsal photograph of TMP 2011.033.0001. Sacral region represents original part—reflected counterpart shown in Fig. 4. Scale equals 1 m. by Caleb M. Brown  https://peerj.com/articles/4066/ via Wiki CC BY 4.0

 

 

Please reload

Feature Stories

VOL. 11

ART of ROBOTICS

Please reload