Science, Tech, Math › Animals & Nature 10 of the World's Most Important Dinosaurs Might Not Be What You Think Learn More About These Paleontologist Favorites From the Mesozoic Era Share Flipboard Email Print Animals & Nature Dinosaurs Basics Paleontologists Carnivores Dinosaurs & Birds Herbivores 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 August 21, 2019 More often than you might think, the dinosaurs the public happens to latch onto as their favorites on the big screen—Apatosaurus, Velociraptor, Tyrannosaurus Rex, etc.—are less important to paleontologists than they are to journalists, fiction writers, and movie producers. Here's a slideshow of 10 dinosaurs that don't get much fanfare but that have made substantial contributions to our knowledge of prehistoric life during the Mesozoic Era. 01 of 10 Camarasaurus MR1805 / Getty Images Diplodocus and Apatosaurus (the dinosaur formerly known as Brontosaurus) get all the press, but the most common sauropod of late Jurassic North America was Camarasaurus. This long-necked plant-eater only weighed about 20 tons (about the weight of three African elephants), compared to 50 tons or more for its more famous contemporaries. After researching an abundance of fossils discovered grouped together along the plains of the American West (Colorado, Utah, Mexico, and Wyoming), paleontologists believe that these egg-laying dinosaurs roamed in vast herds about 150 million years ago. They feasted on fern leaves and conifers and grew to an average of 15 feet tall (the average height of a female giraffe) and between 24 feet to 65 feet long from head to tail (the average maximum length of a school bus in the United States is 43 feet). 02 of 10 Coelophysis Gary Ombler / Getty Images Perhaps because it's so difficult to spell (not to mention pronounce: SEE-low-FIE-sis), Coelophysis has been unjustly neglected by the popular media. The bones of this late Triassic theropod have been found in Arizona but were discovered by the thousands, many of them well preserved, in north-central New Mexico at the famous Ghost Ranch quarry. Coelophysis is considered a direct descendant of the very first dinosaurs, which evolved in South America about 15 million years before this big-eyed meat-eater appeared on the scene. And from the bones that have been analyzed over the years, paleontologists believe the Coelophysis averaged 3 feet high, 9 feet long, and weighed about 100 pounds. They were most likely fast, agile runners that foraged on early relatives of crocodiles and birds and hunted in packs, dominating larger prey with their sharp, jagged teeth. 03 of 10 Euoplocephalus ROGER HARRIS/SCIENCE PHOTO LIBRARY/Getty Images Ankylosaurus is by far the most popular armored dinosaur, and one that has bestowed its name on its entire slow-moving family—the ankylosaurs. As far as paleontologists are concerned, though, the most important ankylosaur was the hard-to-pronounce Euoplocephalus (YOU-oh-plo-SEFF-ah-luss), a low-slung, heavily armored plant-eater (about 20 feet long and 8 feet wide) with a suspended, bony clubbed tail that could swing back and forth—a likely threat to its predators. To date, more than 40 Euoplocephalus fossils have been discovered in Montana and Alberta, Canada, shedding valuable light on the behavior of these formidable dinosaurs. Paleontologists believe that these dinosaurs had a good sense of smell, foraged on ground vegetation, and could use their legs to dig. From one fossil location discovered in 1988, there are some indications that they could have dwelled in herds or at least congregated when young. 04 of 10 Hypacrosaurus DEA PICTURE LIBRARY / Getty Images The name Hypacrosaurus means "nearly the highest lizard (in rank)," to the Tyrannosaurus, and that pretty much sums up this duck-billed dinosaur's fate: It has almost, but not quite, purchased a hold on the popular imagination. One of its more distinguishing features is a tall, jagged ridge of spines trailing the vertebrae and a hollow, bony crest on its long head. What makes the Hypacrosaurus discovery important is that the nesting grounds of this dinosaur—complete with eggs, hatchlings, and juveniles—were discovered in an area of Montana, shedding light on exactly what was happening there 70 million years ago. All of the dinosaurs were instantly killed and the entire scene was well preserved in a volcanic ashfall. Information gleaned from this discovery included: Hypacrosaurus breeding was prolific with nests of up to 20 eggs, while mortality rates were likely high with young Hypacrosaurus hunted by Troodons (small, bird-like dinosaurs) and adults preyed upon by much larger Tyrannosaurs (also known as tyrant lizards). The specimens of the Hypacrosaurus from Montana, as well as specimens found in Alberta, Canada, were examined in detail and have given paleontologists a valuable glimpse into dinosaur family life during the late Cretaceous period. (A close runner-up in this category is Maiasaura or "good mother lizard," another plant-eating duckbill dinosaur that left abundant evidence of its social behavior.) 05 of 10 Massospondylus Nobumichi Tamura/Stocktrek Images/Getty Images Massospondylus (Greek for "longer vertebra") was the prototypical prosauropod: a breed of relatively petite plant-eating dinosaurs that were distantly ancestral to the huge sauropods and titanosaurs of the later Mesozoic Era. They stood about 8 feet high, were about 20 feet long, and weighed about 750 pounds. The discovery of preserved Massospondylus nesting grounds in South Africa revealed a lot about this dinosaur's behavior: For instance, it's now believed that they were bipedal, beginning life on all four legs and then graduating to standing on two. They used their long necks to feed like giraffes on tall greenery and shared food with their offspring, who were born without teeth. Sometimes the Massospondylus was omnivorous, although it's been speculated that some animals could have been mistakenly ingested along with greenery. And because Massospondylus dinosaurs were much more nimble than paleontologists had previously speculated, it's believed that they were fast runners compared to other dinosaurs. They also had hands that assumed the prayer position when relaxed. In action, their five fingers including a sharp-clawed thumb that most likely assisted in running and feeding. 06 of 10 Psittacosaurus DEA PICTURE LIBRARY / Getty Images Also known as the parrot lizard for its beak-shaped jaw, the bones of the plant-eating Psittacosaurus have been discovered in China, Mongolia, and Russia. Although Psittacosaurus wasn't the earliest ceratopsian—the family of horned, frilled dinosaurs typified by Triceratops—it's one of the best known among paleontologists. It comprises about a dozen separate species dating to the early-to-middle Cretaceous period (about 120 to 100 million years ago). Compared with its huge (and hugely popular) descendants, Psittacosaurus was a relatively tiny dinosaur in comparison—on average it was about 6.5 feet long, 2 feet tall, and about 40 to 80 pounds. Its jaw was able to slide forward and backward, so it could have easily grazed on plants, and it's thought that many species may have subsisted entirely on nuts and seeds. Analysis of Psittacosaurus fossils has helped paleontologists learn more about ceratopsian evolution. 07 of 10 Saltasaurus DEA PICTURE LIBRARY / Getty Images Discovered in the Salta region of Argentina, Saltasaurus, or lizard from Salta, was a smallish (40 feet long), long-necked sauropod weighing 10 tons. Its skin was covered with tough, bony armor and was at first mistaken for a specimen of Ankylosaurus. Believed to be an herbivore, its diet would have consisted of ferns, gingkos, and other low-lying greenery, which it ate in abundance—about 500 pounds a day for an adult dinosaur. The Saltasaurus is a member of the sauropod dinosaur family that lived during the late Cretaceous period, whereas the sauropods as a whole peaked in population almost 100 million years earlier, during the late Jurassic period. Also, Saltasaurus is one of the first identified titanosaurs, a group of sauropods that had spread to every continent by the end of the Mesozoic Era. 08 of 10 Shantungosaurus Sergey Krasovskiy / Getty Images Shantungosaurus or Shandong lizard is a true oddity: a late Cretaceous hadrosaur, or duck-billed dinosaur, that was 50 feet long (a little longer than a school bus) and weighed as much as a medium-sized sauropod. Not only did the Shantungosaurus tip the scales at about 16 tons (the weight of about 10 African elephants), but paleontologists believe it was capable of running too, balancing all of that weight on two legs as it was pursued by predators. It's considered the largest bipedal terrestrial animal in the history of the planet. The fossils of the Shantungosaurus were discovered on China's Upper Wanshi Formation of the Shandong Peninsula, revealing jaws teeming with 1,500 tiny teeth—well suited for shredding copious amounts of vegetation. 09 of 10 Sinosauropteryx Alvaro Rozalen/Stocktrek Images/Getty Images Quick poll: How many of you have heard of Archaeopteryx, and how many of you have heard of Sinosauropteryx? You can put down your hands: Archaeopteryx may be famous as the first feathered proto-bird, but Sinosauropteryx (Chinese lizard wing), which lived about 20 million years later, was the genus that made feathered dinosaurs a household phrase around the world. The discovery of this theropod in northeastern China's Liaoning fossil beds caused a worldwide sensation. About the size of a small dog, it was an average of 11 inches tall and 4 feet long from the top of its head to the tip of its long tail and weighed about 5.5 pounds. Some scientists believe that Sinosauropteryx could have been an orange color and had rings of stripes that circled its tail. There seems to be no debate about its diet, however—it feasted on small lizards and mammals. 10 of 10 Therizinosaurus Mariolanzas / Wikimedia Commons / CC BY-SA 4.0 Considering how weird this dinosaur looked with its three-foot-long claws, prominent pot belly, and an even more prominent beak—you'd think Therizinosaurus (scythe lizard) would be as popular with children as their favorite Stegosaurus. The fossils of the Therizinosaurs were first discovered in the Nemgt Formation of southwestern Mongolia with subsequent finds in northern China, on grounds that it roamed during the late Cretaceous period (77 million years ago). Some paleontologists believe this dinosaur was covered in feathers like its close relatives, while others argue that's probably unlikely due to its size: 33 feet long, 10 feet tall with 8-foot-long arms, and weighing about 5.5 tons. It's believed that its diet was mainly treetop greenery, based on the shape of its mouth and teeth, but it's often argued that it could have been a meat eater because of its sharp claws and close relationship with theropod dinosaurs.