News for Schools from the Smithsonian Institution. Office of Elementary and Secondary Education. Washington, D.C. 20560 April 1992 Digging Up Dirt How Paleontologists Bring Dinosaurs Backto Life Each year, thousands of visitors stroll through red mudstone about six dinosaur exhibits in museums across the country. They feet wide and three feet crane their necks to see the top of Brachiosaurus's deep. They theorized that skeleton and marvel at the ferocious look of the red mudstone bowl Tyrannosaurus rex. Adult visitors try to comprehend could have been a nest for the passage of time when it's counted in hundreds of the babies. It looked as if it millions of years instead of hours. Dinosaurs make had been made by the adults think about evolutionary change and abrupt babies' mother who had extinction; they wonder what the dinosaurs' mounded up the earth and experience on earth can teach us. scooped out the middle. Rather than being merely curious, children are They believed the green passionate about dinosaurs. They gaze at the huge mudstone had filled the skeletons, imagining a landscape that could hold such nest during the many creatures. They read and mouth the difficult-to­ millions of years since the pronounce dinosaur names. Children possess babies had died. encyclopedic knowledge about dinosaurs. Any teacher When Horner finished who has studied dinosaurs with a class has been digging through the small corrected by a ten-year-old expert. "Actually, Ms. mound, he had found the Miller, since the 1970s, Iguanodon has been depicted remains of 15 three-foot­ with the tall aloft." Children are fascinated by the long baby dinosaurs. unique place dinosaurs occupy in the panoply of (Adult hadrosaurs of the monsters. Dinosaurs were huge, ferocious, type found in this nest preposterous-looking and, best of all, real. They grow to be 25-30 feet require none of the suspended disbelief that Red long.) These were not 15 Riding Hood's wolf calls upon. Their gigantic forms complete skeletons. They strike awe without causing fear since they are not were disconnected bones merely dead, they are extinct. belonging to 15 babies However, few people understand paleontology, the who had died in the nest science that brought dinosaur remains to human and whose skeletons had understanding. The purpose of this issue ofArt to Zoo J been subjected to time and is to introduce you and your students to this uniquely '0 weather until they fell E speculative science. First you will be introduced to a il apart; then they were practicing paleontologist, John Horner, and his ~ fossilized. remarkable discoveries about how dinosaurs nurtured B John Horner had many their young. The next sections tell how fossils form ·c ~ questions about these baby and how paleontologists find, stabilize, and transport <t dinosaurs. Reading these fossils from the field to the laboratory. In the How manypaleontologists does it take to mount a Diplodocus leg? This huge questions and learning Practicing Paleontology section, students participate in sauropod dinosaur demanded the talents ofseven men. about how he answered activities designed to help them think about the fossil them will help you record the way paleontologists do. The Pull-Out Page Medicine Formation. Choosing a place to look for understand how a paleontologist thinks. If you had invites students to collaborate in science teams and to bones is often the first important choice a made this discovery, what would your questions have create miniature model fossil finds. In addition to the paleontologist makes, and John Homer had chosen his been? fun they will have with boxes of sand, chicken bones, site. Baby dinosaurs had been of special interest to him First, Horner wondered if these were babies' and plaster of Paris plant fossils, students will learn since he had found the Western Hemisphere's first remains or the remains of another kind of very small about geology, paleontology, anatomy, and scientific intact dinosaur egg while out prospecting in 1977. He dinosaur such as Microvenator, who was 3-5 feet long method. had more than a hunch that looking for baby dinosaur when full grown and weighed a mere 12-15 pounds. In fossils in the Two Medicine Formation would payoff. order to answer his questions, he had to "read" the Though his scientific plans had been carefully evidence found at the site: the number, condition, and Background made, John Horner's first discovery of a baby placement of the bones, and the soil type. The first Discovering the "Good Mother lizard" hadrosaur's jawbone occurred while he was thing he did was to look at the development of the John R. Homer is a famous paleontologist (a person rummaging through a coffee can full of dinosaur bones. His close examination told him that these were who studies ancient life) whose analysis of the bones in a rock shop in Bynum, Montana. The shop indeed the bones of baby dinosaurs. The signs that he dinosaur remains he found in Montana have led many owner had discovered the bones and saved them. She read were found in the vertebrae (bones of the spine) people to believe that at least some dinosaurs took care was glad to show them to Homer, and he identified near the base of the spine. These vertebrae were not of their babies after they were hatched. Before Homer them for her. He believed the tiny bones belonged to a yet fused together as they are in mature dinosaurs. made his discoveries, most paleontologists believed baby duckbilled dinosaur, or hadrosaur, a common When he saw that the ends of the limb bones were not that dinosaurs, like most reptiles, merely deposited type ofdinosaur during the Late Cretaceous Period, 84 fUlly formed either, Horner knew these were the their eggs and left the infant dinosaurs to fend for to 72 million years ago. She took him to the place remains of very young dinosaurs. themselves. Learning about John Homer's discoveries where she found the fossils, and John Homer's But these were not merely newborn babies who had will teach you a lot about dinosaurs, but it will also search for the babies began. met sudden death right after their birth. Homer teach you how paleontologists think and how they John and his partner Bob Makela found . found a sign of their age from a source fossils (which looked like grayish­ pose the questions that shape what they look for, and that yields a great deal of thus, what they find. black bits of stone) sitting right on information; he looked at the In 1978, John Homer, a paleontology technician top of the small mound they had babies' jaws and teeth. He working at Princeton University, was interested in been shown. When they dug into found that their teeth were finding the remains of baby dinosaurs. He had read the mound to see what the ground worn down from chewing. held, they discovered many baby about the few places such remains had been found in In order to show wear on the past, such as Mongolia, Canada, Montana, and dinosaur bones mixed their teeth, these babies must New Mexico. His research had given him the idea that haphazardly into green mudstone. have been chewing for some he might find more juvenile dinosaur remains in a Digging deeper, however, they This drawing ofthe dinosaur nest shows the red time. Their worn teeth fossil-rich rock formation in Montana, called the Two saw that the green mudstone sat mudstone "bowl" that held the mixed-up remains within a large, shallow bowl of of 15 baby dinosaurs. Braginetz and Ellingsen, Digging Dinosaurs Continued on page 2 continued from page 1 bury its body. The carcass can be buried deeper and deeper on the riverbank as the sediments gather over it showed that they could not have died immediately or it is covered by the soft sand of the river bottom. after birth. The soft parts of the animal's body the organs, Another aspect of this find was interesting and muscles, and skin - decay rapidly, but the animal's perplexing. The nests were mled with bits of crushed bones may remain intact under the protecting eggshell. How would you have explained the crushed sediments. eggshells? Homer believed that the babies had stayed Over many millions of years, water passing through in their nests for the early part of their life and that the accumulating sediments affects the dinosaur bones. they trampled their own eggshells after they were The water dissolves some of the chemicals in the bone born. and replac~s these chemicals with others. The new Now, here are the next thoughts that went through chemicals in the bone preserve the bone's shape and Horner's mind. The babies' teeth were worn down size but give it a different chemical make-up. from eating; fifteen of them had been fOl~nd in the Sometimes the chemicals petrify the bone, turning it to same nest, and all the eggshells in the nest were stone and making the bone much heavier and denser broken up. It sure looked like the babies had stayed in Talk about walking in yourparents' footsteps! On the than it was when the animal lived. The "new" petrified the nest for a long time. And if they actually did stay left, above the four-inch ruler, is the hind foot ofa baby bone usually has the same shape as the original, even in the nest, someone had to bring them food for them duckbill dinosaur. On the right, you are looking at one down to the tiny spaces for blood vessels within the to survive - someone, Horner believed, like their toe bone ofan adult duckbill! bone.