Science, Tech, Math › Animals & Nature Tenontosaurus Share Flipboard Email Print Tenontosaurus (Perot Museum). Animals & Nature Dinosaurs Herbivores Basics Paleontologists Carnivores Dinosaurs & Birds Marine Reptiles Prehistoric Mammals Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated March 17, 2017 Name: Tenontosaurus (Greek for "tendon lizard"); pronounced ten-NON-toe-SORE-us Habitat: Woodlands of North America Historical Period: Middle Cretaceous (120-100 million years ago) Size and Weight: About 20 feet long and two tons Diet: Plants Distinguishing Characteristics: Narrow head; unusually long tail About Tenontosaurus Some dinosaurs are more famous for how they got eaten than for how they actually lived. That’s the case with Tenontosaurus, a medium-sized ornithopod that was on the lunch menu of the respectably sized raptor Deinonychus (we know this from the discovery of a Tenontosaurus skeleton surrounded by numerous Deinonychus bones; apparently predators and prey were all killed at the same time by a natural cataclysm). Because an adult Tenontosaurus could weigh in at a couple of tons, smaller raptors like Deinonychus must have had to hunt in packs to bring it down. Other than its role as prehistoric lunch meat, the middle Cretaceous Tenontosaurus was most interesting for its unusually long tail, which was suspended off the ground by a network of specialized tendons (hence this dinosaur's name, which is Greek for "tendon lizard"). The "type specimen" of Tenontosaurus was discovered in 1903 during an American Museum of Natural History expedition to Montana led by the famous paleontologist Barnum Brown; decades later, John H. Ostrom did a closer analysis of this ornithopod, corollary to his intensive study of Deinonychus (which he concluded was ancestral to modern birds). Oddly enough, Tenontosaurus is the most abundant plant-eating dinosaur to be represented in a vast stretch of the Cloverly Formation in the western U.S.; the only herbivore that's even close is the armored dinosaur Sauropelta. Whether this corresponds to the actual ecology of middle Cretaceous North America, or is just a quirk of the fossilization process, remains a mystery.