Describes unusual feeding in carnivorous dinosaur
CHICAGO – An extremely well-preserved, 70-million-year-old fossil found in the Gobi Desert by Peter Makovicky – The Field Museum’s new assistant curator of dinosaurs – has shed light on what an ostrich-like dinosaur ate and where it lived.
The find occurred while Dr. Makovicky was participating in a paleontological expedition conducted last summer by the American Museum of Natural History and the Mongolian Academy of Sciences.
Dr. Makovicky, who joined The Field Museum last month from AMNH, co-authored a paper in Nature Aug. 30, 2001, describing rare soft tissue that was preserved in two dinosaur fossils. The fossil Dr. Makovicky found includes a thin, comb-like structure on the beak that had never before been seen in a dinosaur.
The structure is similar to the filter-feeding beak of a contemporary duck’s bill. It indicates that these toothless dinosaurs may have eaten by straining tiny invertebrates and other food particles from water and sediment. The plate was found in Gallimimus bullatus, an ornithomimid or bird-like dinosaur with a small head. Ornithomimids are sleek creatures that resemble an ostrich with a long tail. Their long legs make them some of the fastest-running dinosaurs.
Gallimimus stood about 7-feet tall but was 15-feet long – a very large animal to be straining miniscule food particles from the bottoms of streams and ponds. The specimen found by Dr. Makovicky is not fully grown, however, and was only about half that size.
Ornithomimids belong to a group of dinosaurs called theropods, the carnivorous dinosaurs that include Tyrannosaurus rex, Velociraptor mongoliensis, and living birds. Along with Oviraptors and birds, ornithomimids are the only toothless theropods.
“We are used to conceiving of theropods as dinosaurs with big teeth adapted to hunting large prey, but these beaked theropods adapted very differently and may have lived on tiny invertebrates similar to brine shrimp,” Dr. Makovicky says. “Present day birds are theropods that have adapted to a wide range of habitats and foods, so it makes sense that theropods adapted widely in the age of dinosaurs, too,” he adds. Lifelong interest
Dr. Makovicky wanted to study dinosaurs ever since the day when, as a child, his Mother bought him a bag of toy dinosaurs. Although Dr. Makovicky grew up in Denmark, where there are no dinosaurs, his interest in paleontology flourished. He has searched for dinosaurs around the world, including Mongolia, Argentina and Canada, where he worked with Philip Currie, world-renowned curator of dinosaurs at the Royal Tyrrell Museum of Palaeontology in Alberta.
In 1995, Dr. Currie’s team discovered Ornithomimus edmontonicus, the other ornithomimid described in the Nature paper. Dr. Currie co-authored the paper, along with lead author Mark Norell, paleontology chair at AMNH.
Over the years, many other ornithomimid fossils have been found, but the soft-tissue structures on the two fossils described in Nature have never before been preserved. As a result, scientists have long debated what ornithomimids ate and what their beaks looked like. The skulls of both fossils have traces of keratin (the same material found in human hair and fingernails) along the edges of their beaks.
“These two well-preserved specimens allow us to say, for the first time, what the beak covering was on these dinosaurs, as well as to speculate on their feeding behavior,” says Dr. Norell. “Ornithomimids are found in rocks that represent wet environments, where they were ecologically tied to food supplies.”
The fossils were exceptionally well preserved because the dinosaurs died complete, were buried quickly in mud or sand, and remained undisturbed, Dr. Makovicky says. “Finding Gallimimus bullatus is one of those things you always dream about. That’s what I love about paleontology: you can find something completely unexpected. It’s a world where truth is better than fiction.”
Dr. Makovicky will be adding to the dinosaur collection at The Field Museum – home of Sue, the largest, most complete and best-preserved Tyrannosaurus rex ever found. Acquired in 1997, the famous, 67-million-year-old fossil has taught scientists much about the lives and times of dinosaurs.
Editor’s note: images available of Dr. Makovicky and Gallimimus bullatus.
Journal
Nature