Field Museum Scientists Discover What Appear to be World’s Oldest Dinosaur Fossils Field Museum scientists have discovered what appear to be the oldest dinosaur fossils ever found. The fossilized remains – jaw bones from two new plant-eating dinosaurs – date from Middle to Late Triassic period, 225 to 230 million years ago. The discovery, described in the October 22 issue of Science, was made by a team of paleontologists working in Madagascar during four separate expeditions from 1996 to1999. In addition to the fossilized jaw bones, the team discovered the exquisitely preserved remains of eight other prehistoric animals of the same age, providing a freeze-frame picture of life during the earliest days of dinosaurs and mammals – a picture that has been largely obscured until now. The new fossil discoveries greatly enhance The Field Museum’s place at the forefront of paleontology research. The Field Museum will exhibit the fossils to the public October 22, 1999 through January 2, 2000. The special exhibition is located near the Museum’s McDonald’s Fossil Preparation Laboratory, where visitors can watch scientists prepare and clean other fossils from Madagascar. The fossils were found by John J. Flynn, MacArthur Curator and Chair of the Department of Geology at The Field Museum; William F. Simpson, Collections Manager, Fossil Vertebrates, The Field Museum; J. Michael Parrish, of Northern Illinois University; Berthe Rakotosamimanana, of the Université d’Antananarivo in Madagascar; and Robin Whatley and Andre Wyss of the University of California at Santa Barbara. The research was funded by The National Geographic Society and long-time Field Museum supporters John and Withrow Meeker. The Field Museum is currently involved in a collaborative U.S.-Malagasy project. "The most exciting part of this project is that we are only beginning to fill in huge gaps in the fossil record of Madagascar – an island that was once thought to be fossil poor, but is turning out to be a treasure trove," Flynn said. The Middle to Late Triassic has long been a puzzle for paleontologists. At the opening of this period, a wide variety of vertebrates (animals with backbones) populated the land. By the close of the period, early dinosaurs and mammals had appeared, but a sparse fossil record has left scientists with few clues about what happened in between. In contrast, the newly discovered fossils provide a virtual "Who’s Who" of the Middle-Late Triassic animals in Madagascar. To begin with, the research team found two new dinosaurs that appear to be older than Herrerasaurus and several other forms – the current record holders for dinosaur seniority. The new dinosaurs were prosauropods, plant eaters with small heads and long necks that could walk on two or four legs. These primitive dinosaurs either shared a common ancestor with, or were themselves ancestors to, the mighty sauropod dinosaurs that evolved later, such as Apatosaurus. The fact that these fossils belong to one of the major branches of the dinosaur evolutionary tree indicates that the earliest origins of the Dinosauria must be even older. The scientists have not yet given formal names to their new finds. The team of scientists also found fossils from several other vertebrates the same age as the two new prosauropods. These include three members of the branch of animals that includes modern day reptiles, and five members of the branch that includes mammals. Several of these animal lineages were thought to have died out by the time dinosaurs appeared. So when Flynn and his colleagues found evidence that the two groups co-existed, they knew it meant the animal fossils were unusually young, or the dinosaur fossils were unusually old. Previously, radioisotope dating has shown the oldest known dinosaurs, Herrerasaurus and its contemporaries to be just under 228 million years old. So Flynn and his colleagues were faced with the enticing question: Could the new prosauropods be even older? Because the rock layers at the Madagascar sites have not yet yielded the right minerals for radioisotope dating, the paleontologists had to use other clues from the fossil record to determine the age of their finds. Judging from the anatomical details of the fossils, two of the animals (one a parrot-beaked reptile, the other an early relative of mammals) appear to be more primitive cousins to similar animals already known to be younger than 228 million years old. Also, the Madagascar record is so far lacking in fossils of aetosaurs – small armored reptilian herbivores that were abundant beginning about 228 million years ago. The absence of aetosaurs led scientists to believe the newly found fossils were even more ancient. Flynn and the other team members therefore concluded that their find is probably closer to 230 million years old, which would make the two new prosauropods the oldest dinosaurs ever discovered. "These exciting new finds extend the record of prosauropod dinosaurs back much further than previously known," said James Hopson, Professor, Department of Organismal Biology and Anatomy, and Committee on Evolutionary Biology (CEB), University of Chicago. The five pre-mammalian animals that the researchers discovered should also shed much-needed light on the currently murky picture of the origins of the first true mammals. For example, an essential question is how this line of large, cold-blooded "mammal-like reptiles" evolved into small warm-blooded mammals, many of which then evolved to much larger sizes once again, following the extinction of the dinosaurs. "The new fossils will help us complete the picture of that evolutionary transformation. The fossils are exquisitely preserved. They show a level of detail far superior to everything else from that time," said Flynn. Hopson agreed, "The cynodonts (the group of prehistoric animals including mammals and their nearest relatives) are some of the best specimens I have ever seen. They will be very important in working out how these close relatives of mammals were related to one another and how they were distributed across the supercontinent of Pangea at that time." Pangea is the name given a huge landmass that existed before breaking apart into the separate continents. The scientists chose to search for fossils on the island of Madagascar because it separated as an island so long ago. Madagascar hasn't been connected to Africa since the latest Jurassic period (160 million years ago) and is therefore an excellent place to study evolution before, during and after its isolation from other landmasses. TOP