Museums don't just display skeletons. They often display paintings of what the dinosaurs looked like in their environments. Or fully fleshed out three-dimensional models of the dinosaurs. And the question is, how to paleontologists take a few dry bones and a little bit of information. And turn those into fleshed out, very colorful very often. Animals that try and give us an understanding of what they were like when they were alive. >> Dinosaur fossils usually consist of only the bare bones. Bones are hard, mineralized structures that rot away slowly. Muscles, organs, and skin decay quickly and seldom fossilize. However, under the right conditions, paleontologists do get a rare glimpse of a dinosaur's soft anatomy. Footprints are natural molds of dinosaur feet. Usually dinosaur tracks provide nothing more than the sloppy outline of the dinosaur's toes. But sometimes tracks are so well preserved that they include impressions of the scales from the sole of the dinosaurs foot. In very rare cases, entire dinosaurs bodies, skin and all, were buried by mud soon after death. And skin impressions formed before the flesh had time to rot away. Sometimes true fossils of the skin, not just molds can form. We refer to dinosaur skeletons with lots of associated skin as mummified. These are rare specimens with large regions of the skin hanging off the bone. Mummified dinosaurs were first found in Wyoming in 1910. They were hadrosaurs. These specimens gave paleontologists their first good views of what dinosaurs looked like in the flesh. Claws, beaks, hair, and feathers, are composed of keratin. Keratin is harder than flesh, but it still decomposes much faster than bone and rarely fossilizes. Again, rare conditions are needed to preserve a record of these integumentary structures. Often, the discovery of these structures in a dinosaur fossil reveals an adaptation that we would never have guessed for a dinosaur to have. For instance, a specimen of Psittacosaurus. A small and older relative of triceratops, has been found with fossilized remains of tall, keratinous bristles along its tail. No one is sure what the function of these bristles were. And then, of course, there are feathers. We have discovered lots of fossil dinosaur feathers. Here are two illustrations of one of the most famous dinosaurs, Velociraptor. Which of these do you think is more scientifically accurate? Is it the non-feathered Velociraptor, or the feathered Velociraptor? In this case, the one with the feathers is more accurate. Recent fossil finds of dinosaurs with feathers have lead to the understanding that many dinosaur groups, not just birds had feathers. >> These are two fossil birds from the early cretaceous of China and they're quite remarkable specimens in number of ways. First of all because they're so complete. Here's a skull, neck, main part of the body, wing and the leg of one bird. And, in this case, the skull is looking at us. The wings kind of folded up, and the legs are extended down as well. The remarkable thing, is that, at this site, things preserve in a very different way. So if you go to the claws on the hand of the wing, right here. There's a slight discoloration in the rock, and what that is is the preservation of the keratinous nail, fingernail, of this bird. And that makes these claws incredibly sharp, just like they were in the living animal. What's also remarkable, though, is the fact that the feathers are preserved. You can see the longer feathers as impressions, mostly, behind the wing. But, closer to the body, you can see the downy feathers and the contour feathers that are around the body. We can see the bones in between, because the feathers don't cover the whole body. And, that's a preservational thing. In this site, which consists mostly of lake bed deposits of fine grained silts, you have volcanic ash mixing in with the silt. And the volcanic ash is very good because, like the mud, it preserves detail very well. However, it also alters the chemistry of the water. So, whereas things like the fingernails and the feathers would normally be destroyed by decomposition by bacteria. The bacteria can't live in this cir, kind of circumstance. So as long as the feathers are sandwiched between two layers of sediment, sediment above and sediment below. The feathers preserve as a corona or halo around the outside of the body. And that gives us a very good understanding of what these birds look like. >> Here's a tough question. Based on the current fossil record, which of these dinosaurs should probably be drawn with feathers? Tyrannosaurus, Stegosaurus, Velociraptor, or Edmontosaurus? Check all the answers you think are correct. Velociraptor should definitely be drawn with feathers. Tyrannosaurus probably should be, too. Although we have no direct evidence of feathers in Tyrannosaurus. We have good evidence showing the ancestors of Tyrannosaurus had feathers. And it is likely that Tyrannosaurus kept these adaptations. So A and C are the correct answers. Are we certain that Stegosaurus and Edmontosaurus did not have at least some feathers? No. But the fossil skin impressions that we have for both these animals and their close relatives gives no indication that they did. Although lots of theropod dinosaurs are known to have feathers. There are also lots of dinosaur skeletons that preserve scaly skin impressions, like the one I have here. We find scaly skin most often in hadrosaurs, and there are lots of amazing specimens preserving large skin impressions. We have so many hadrosaurs with skin impressions, that he paleontologist Phil Bell, formally of the University of Alberta. Has described the differences in scale patterns between two closely related species of hadrosaurs. Saurolophus osborni from North America. And Saurolophus angustirostris from Mongolia, we also know that ceratopsians had scaly skin. Although we don't have as many examples as we do for Hadrosaurus. Ankylosaurus, stegosaurus and sauropods also has scaly skins. The only group for which we don't have any skin impressions right now are the Pachycephalosaurs. We're going to talk a little bit more about Ankylosaurus and Stegosaurus for a moment because their skin is so different. Ankylosaurus and Stegosaurus both have bones called osteoderms which means skin bones. And I have an example of an osteoderm from an Ankylosaurus here. That's because these are bones that are formed completely within the dermis, which is the lower layer of the skin. We don't have anything like this in our bodies. All of our bones are internal. Some modern animals have osteoderms, like armadillos, crocodiles, and some lizards like the gila monster. Although they might look similar, turtle shells are not osteoderms, and they form through a different process. Osteoderms are what give ankylosaurs and stegosaurs their spiky appearance. They form the giant plates on the back of the stegosaurs. The spikes on the stegosaur tail, the knob of bone at end of the ankylosaur tail, and all of the small and large spikes on the ankylosaurs. Some of the sauropods also evolved osteoderms. And these were huge. Growing extra bones uses up a great deal of energy. Why might osteoderms be a good thing to have? Check all the answers you think might apply? A storing calcium. B gathering heat from the sun. C protection from biting and clawing predators. Or D, to look good. All of these are possible functions of osteoderms. So each of these answers are correct. In most cases, osteoderms were protective. They shielded their owners from predatory attacks. Some dinosaurs, sauropods are a possible example may have used osteoderms as a repository for calcium. We'll look at this adaptation later in the course. It is also been suggested that some osteoderms which were covered with skin or with blood vessels. May have functioned like solar panels and help to absorb heat from a sun. Last but not least, dinosaurs with large and dramatic osteoderms, like Stegosaurus, may have flaunted their osteoderms as display structures. Using them to attract mates or intimidate rivals. Let's take a moment to recap some of what we know about dinosaur skin and structures in or on the skin. We know that many dinosaurs had scaly skin, and that some theropods had feathers. A few dinosaurs had some unusual bristle-like structures. And finally, the Ankylosaurus, Stegosaurus, and some Sauropods, had bones in their skin called osteoderms. All of these features, scales, feathers, bristles and osteotomes are called integumentary structures. Before we finish this lesson, let's talk about dinosaur colors. Until just a few years ago most of these reconstructions of Sinosauropteryx would've been plausible. Feather colors are not preserved in fossil feathers, so they could have been any color, for all we knew. However, in modern birds, feather color is influenced by the shape and arrangement of pigment cells called Eumelanosomes. We know that in modern birds, long and narrow eumelanosomes correspond to black and gray. While short and wide eumelanosomes correspond to brown and reddish brown. White feathers had no eumelanosomes. We also know that iridescence or glassiness like the shiny black feathers of crows and ravens. Corresponds to narrow eumelanosomes aligned in the same direction. So far, paleontologists have been able to figure out the feather colors of a few species of theropod dinosaurs. By studying evidence of their eumelanosomes. The theropod Anchiornis was black and white with some reddish brown in its head. The four wing dromaeosaur Microraptor was glossy black. And our like this one I have here, had at least some black feathers. Understanding fossil feather colors is such a new field of study that we do not yet know of any fossil feather that were blue, green, or red. But this does not mean that they did not exist. How do we know what colors dinosaurs were? Here are some pictures of sinosauropteryx, the feathered dinosaur from China, we talked about earlier. Given the evidence that paleontologists have gathered so far, which of these drawings do you think is most plausible? A, Green with white spots. B, Black with red stripes. C, Red-brown with white stripes. Or D, Brown with blue highlights. The most plausible coloration for this dinosaur is C, since evidence for other colorations that include green, blue, and red does not exist yet. While we're learning more and more about feather color through the study of eumolanisomes. We still don't have any clue as to what color dinosaur skin might have been.
