Astrodon

Associated Smithsonian Expert: Matthew T. Carrano, Ph.D.

Dr. Matthew Carrano touches the Cretaceous/Paleogene boundary in the field near Hell Creek, Montana

Photo by Matthew Carrano, Smithsonian Institution

Dr. Matthew Carrano’s interest in dinosaurs was sparked when, as a second grader, he read a National Geographic book with illustrations by Jay Matternes. As an undergraduate at Brown University, he studied the functional morphology of dinosaurs, and went on to earn his Ph.D. at the University of Chicago. Since 2003, Matthew has been Curator of Dinosauria at the Smithsonian National Museum of Natural History. He currently studies the evolutionary history, functional morphology, and ecology of dinosaurs. His fieldwork has taken him to the Western Interior of North America, Chile, and Madagascar in search of new dinosaurs and the Mesozoic ecosystems of which they formed an important part. He is also studying the quality of the dinosaur fossil record, and is particularly interested in filling in the "gaps" of certain regions and time periods. Over the last 20 years, he has conducted research in museum collections around the world, including England, France, Germany, Belgium, Portugal, Argentina, Canada, Australia, Zimbabwe, and South Africa.

Meet our associated expert

This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.
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Depiction of evolution from amphibian to sauropod dinosaur
Artwork by John Gurche, Smithsonian. Photography by Chip Clark, Smithsonian

About Sauropod Dinosaurs (Infraorder Sauropoda): Paleobiology

Sauropod dinosaurs were plant-eaters (herbivores) that included the largest land animals that have ever lived. First appearing in the Late Triassic Period (about 210 million years ago), sauropods diversified into many forms during the Jurassic. Still, they maintained a basic body form of with a long neck, a long tail, and a small head. Some sauropods may have browsed like giraffes, using teeth adapted for cutting and stripping plants of their leaves; others may have grazed for low-growing plants which they took whole and chewed. Early studies of sauropods proposed they were aquatic, using the logic that their huge bodies could not be supported on land. Later work revealed that they were probably fully terrestrial, living in a wide variety of land ecosystems. Fossil trackways show that some sauropods traveled in herds composed of animals of different ages. Sauropods often nested together as well, evidenced by clusters of nests with fossil eggs and embryos.

Fossil skeleton of a Permian synapsid that predated the dinosaurs (Dimetrodon sp.)
Photo by Smithsonian Institution, Department of Paleobiology

About Dinosaurs (Dinosauria): Paleobiology

Dinosaurs are land reptiles that include some of the biggest terrestrial life forms ever on Earth. We know dinosaurs from fossilized bones, teeth, footprints, eggs, and occasionally even soft tissues, although complete skeletons are rare. The earliest known dinosaurs are from the late Triassic (about 230 million years ago), when they were still overshadowed by other animals, such as synapsids (related to the ancestors of mammals). By the end of the Triassic, dinosaurs had begun their remarkable diversification, with several major lineages present. The Jurassic and Cretaceous periods saw dinosaurs dominate many land environments, reach enormous sizes, and diversify into thousands of species (including the first birds). Paleontologists have named more than 1200 species of dinosaurs, and that’s probably just a fraction of all the dinosaur species that existed. Most dinosaurs went extinct abruptly 66 million years ago (end of the Cretaceous), along with many other species. A period of severe environmental stress, punctuated by an asteroid impact, was likely responsible for this mass extinction.