Towering above all else, dinosaurs are well-known to be the largest land animals. In popular culture, the Tyrannosaurus rex is portrayed as paralyzing in both manner and size. In all actuality, the T. rex does not even make the top fifteen list of these massive creatures. The following information provides a glimpse of the largest dinosaurs, measured first by length, with height and weight taken into account next. Other sources may provide different sizing information, simply because they have a different system of measurement. With height measured from the top of the head to the ground, the fifteen biggest dinosaurs that ever walked this earth are as follows:
Length: 60 feet
Height: 23 feet
Weight: 20 tons 
With a name that means “chambered lizard,” the Camarasaurus was an herbivore (plant-eater) and a quadruped, meaning it walked on all fours. This dinosaur is the most well-known sauropod that comes from the late Jurassic period in North America .
The Camarasaurus acquired its name due to the large openings that were discovered in its head. These are suspected to have helped it cool down. It also had hollow vertebrae in order to lessen some of the weight from its backbone. It is believed that during the time of its existence, plants were more difficult to chew, which made it necessary for the Camarasaurus’ teeth to adapt to this tough quality of vegetation. Paleontologists also suspect that this particular type of dinosaur swallowed gastroliths, or small stones that helped it grind its food. Camarasaurus likely traveled in herds and is thought to have been attacked and eaten by the carnivorous theropods that also wandered the plains of North America .
Length: 65 feet
Height: 25 feet
Weight: about 15 tons 
The Titanosaurus, like the Camarasaurus, was an herbivore and a quadruped. Its name translates to “titanic lizard.” Part of the order Saurischia, it was found in Argentina and India. Resembling a Diplodocus in form, its back was lined with small, armored plates .
This species of dinosaurs was the main member of the titanosaur family. This particular group of dinosaurs is notable because they were the last sauropods on the planet before the occurrence of the Cretaceous-Tertiary Extinction Event (also known as the K/T Extinction Event) 65 million years ago. Oddly, though the remains of the Titanosaurus have been found, its skull has not yet been located. This is a common trend with several different types of dinosaurs and allows only a partial picture of the Titanosaurus to be revealed. Their weight is, therefore, an estimation based on the assumed size of the head. The bony armor covering the Titanosaurus is probably what kept them safe from theropods and other predators and allowed them to live up to the point of the K/T Extinction Event.
Length: 66 feet
Height: 35 feet
Weight: about 20 tons 
The Bothriospondylus (meaning “excavated vertebrae”) was an herbivore and a quadruped and is also known as a Marmarospondylus. Fragments of the Bothriospondylus’ fossils were found in Madagascar and Western Europe. It has been estimated that its forelegs and hind legs were approximately the same size .
These dinosaurs lived during the late Jurassic period and are classified as sauropods. Their large size, as well as their long neck and tail, have led the Bothriospondylus to be described as similar to a Brachiosaurus. In 1875, paleontologist Richard Owen analyzed four substantially sized vertebrae that were uncovered in an English geologic formation. Owen described four different species of Bothriospondylus, which were soon afterwards given a new classification that are currently as extinct as the dinosaur itself. Because of this shifting categorization and the doubt surrounding this type of dinosaur, studies of the Bothriospondylus are often shoved aside in order to spend time examining dinosaurs that have a more solid determination of their characteristics and classification .
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Length: 69 feet
Height: 28 feet
Weight: 30 tons 
The Alamosaurus, or “Alamo lizard,” was an herbivore and a quadruped that lived during the late Cretaceous period. Remains have been found in New Mexico, Texas, and Utah. As North America’s only titanosaurid, the Alamosaurus has gotten a lot of attention as such. It was also one of the last sauropods to exist when the Age of Dinosaurs came to an end. There is a possibility that this dinosaur came to North America from South America.
One study ponders the large number of the Alamosaurus that existed in Texas at any point in time. It is estimated that there were up to 350,000 of this type of dinosaur in that area. However, the name of the Alamosaurus is merely a coincidence. It was named after the sandstone formation called the Ojo Alamo, which exists in New Mexico. The Alamosaurus appears to be closely related to the Saltasaurus, another titanosaur that walked the woodlands of South America .
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Length: 69 feet
Height: 30 feet
Weight: about 26 tons 
The Laplatasaurus (“La Plata lizard”) was named after the location of its discovery: near the La Plata River in Argentina. It is an herbivore and a quadruped, and it is a member of the family of titanosaurs. Its skin was hardened in some places, where bony plates were thought to provide protection. The Laplatasaurus is known to be a sauropod, and it lived in the late Cretaceous period. Not much outside of the basic order and family information is known about this type of dinosaur .
The Laplatasaurus is believed to have had a long neck and a short tail. Its vertebrae, though armored, were relatively light, allowing it to more easily transport its massive body across land. Fossils of the Laplatasaurus were discovered in 1927 by the paleontologist Friedrich von Huene. Along with its location in Argentina, it is possible that this dinosaur also lived in Madagascar at one point .
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Length: 69 feet
Height: 35 feet
Weight: 30 tons 
The Mamenchisaurus, or “Mamenchi lizard” was an herbivore and a quadruped that lived during the late Jurassic period. Most notable about this dinosaur, perhaps, is the size of its neck, which measured up to 36 feet and held 19 vertebrae. This is longer than the neck of any other dinosaur that has been found thus far. Because of the similarity of its foot and ankle bones to those of a Diplodocus, the Mamenchisaurus is classified as a diplodocid .
Named after the province of China where it was first found in 1952, the Mamenchisaurus has since been classified as a sauropod. Though its size was not particularly remarkable, the length of its neck makes it a popular topic of conversation. Paleontologists suspect that, rather than holding its neck straight up to eat leaves from tall trees, the Mamenchisaurus ate vegetation that grew on the ground. These eating patterns may explain how this dinosaur was able to survive while still allowing oxygen to pump through its entire bloodstream .
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Length: 72 feet
Height: 35 feet
Weight: 22.5 tons 
The Haplocanthosaurus (“single-spined lizard”) was an herbivore and a quadruped that lived during the late Jurassic period. It is the most primitive sauropod that has been discovered in North America at this point, and it is the sole member of the Cetiosauridae group that represents the basal sauropods. It was initially thought to be much smaller than it actually is, with recent discoveries pointing to its actual size. With its fossils found in Colorado, Wyoming, and Utah, the Haplocanthosaurus has been proven to have single-spined vertebrae, as well as a heavy trunk and a relatively short neck and tail, in comparison to the rest of its body .
This sauropod, while similar to the Brachiosaurus, is much smaller than its popular cousin. At this time, there is only one fully composed adult Haplocanthosaurus skeleton, and it is displayed at the Cleveland Museum of Natural History, where it is referred to by the name “Happy” .
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Length: 75 feet
Height: 15 feet
Weight: 33 tons 
The Apatosaurus, or “deceptive lizard,” was initially known as the Brontosaurus. It was an herbivore and a quadruped that lived during the late Jurassic period. Its main source of defense was its whip-like tail, which measured approximately thirty feet in length. Remains of the Apatosaurus have mainly been found in western North America. At the top of its twenty-foot-long neck rested a small head with a brain that was comparable in size to a large apple. In order to support its neck and tail, the Apatosaurus had two low ridges along the entirety of its backbone .
The confusion surrounding the name of the Apatosaurus is explained by the early error of Othniel C. Marsh, the paleontologist who is credited with discovering this dinosaur. When he first located the dinosaur’s bones in 1877, he called it an Apatosaurus. Later on, when he found larger bones of a similar nature, he named his discovery “Brontosaurus.” In all actuality, these bones belonged to an adult Apatosaurus, so scientists made the decision to change the name back to its original name .
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Length: 89 feet
Height: 24 feet
Weight: 25 tons 
The Diplodocus (“double beam”) was an herbivore and a quadruped that lived during the late Jurassic period. They are thought to have roamed the western United States and are one of the longest dinosaurs known to have existed. Their exact length is uncertain, however, because a full Diplodocus tail has not yet been found. With hind legs that were longer than those in front, it had ample access to plants both low and high. Other characteristics it was known for include the following: elongated snout, peglike teeth, and a small brain .
After analysis of the Diplodocus’ teeth, paleontologists have come to the conclusion that this dinosaur had a deliberate way of removing leaves with its teeth in order to keep it fed constantly. While it is possible that the Diplodocus lowered its head to eat ground-level leaves, there are disagreements about whether they actually did keep their head low or if their sights were set on taller trees and plants .
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Length: 89 feet
Height: 40 feet
Weight: 25 tons 
The Barosaurus, or “heavy lizard,” was an herbivore and a quadruped that lived during the late Jurassic period. As far as sauropods go, they are comparatively rare. Its remains have been found in both the Black Hills of South Dakota, as well as in East Africa. This provides possible evidence that the continents of modern-day Africa and North America were connected during the late Jurassic period, if not before .
The Barosaurus is identical to the Diplodocus, with the exception of its neck, which measures thirty feet in length. Another similarity that the Barosaurus shared with its sauropod family was its small brain, located inside an equally small head (in comparison to the rest of its body). Because of the length of this dinosaur’s neck, scientists have called into question the means of pumping blood throughout the entire body, all the way to the top of the head. In order for it to function properly, the heart of a Barosaurus would have had to weight 1.5 tons. It is possible that dinosaurs may have had a different make-up than animals today, with “subsidiary” hearts along their necks .
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Length: 100 feet
Height: 50 feet
Weight: 50 tons 
The Brachiosaurus (“arm lizard”) was an herbivore and a quadruped that walked the planet during the late Jurassic period. Its full skeleton was found in Tanzania and is admired for its enormous mass. Just a single vertebra in its neck stretched to a length of more than three feet long. Because some sources say that this dinosaur’s nostrils were on top of its head, it is thought that it may also have immersed its body in water. However, that has been discredited by some scientists who believe that the Brachiosaurus would not be able to breathe in those depths because of the water pressure .
Other sources have shown that the nostrils of the Brachiosaurus were in fact on the end of its snout rather than on top of its head. At one point, the Brachiosaurus was perceived as an underwater animal that used the top of its head as a snorkel. This has since proven to be untrue, though new details continue to unfold as fossils are uncovered and explored, as is the case with any of the dinosaurs .
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Length: 100 feet
Height: 53 feet
Weight: 70 tons 
The Ultrasaurus, or “ultra lizard,” was an herbivore and a quadruped that was alive during the late Jurassic period. Digger Jim Jensen (Brigham Young University) uncovered this immense dinosaur in Colorado. Previously known as an “Ultrasaurus,” the spelling had to be altered because the initial name had already been taken by a South Korean specimen. Some experts believe that the Ultrasaurus may have been a large Brachiosaurus .
Evidence shows that the Ultrasaurus, like other sauropods, laid eggs while they were walking and did not take care of their eggs. At one point, paleontologists thought that sauropods such as this one had a second brain. This has since been identified as an enlargement of the spinal cord that was located around the area of their hips. Comparing the small size of the Ultrasaurus to its significant body size and weight, it is estimated that they have amongst the lowest intelligence of all dinosaurs .
Length: 100 feet
Height: 66 feet
Weight: 60 tons 
The Supersaurus (“super lizard”) was an herbivore and a quadruped that lived during the late Jurassic period. Just like its relative, the Ultrasauros, the Supersaurus was discovered in 1972 by Jim Jensen in Colorado. Notable characteristics include a long neck that was topped with a small, narrow head. Its tail was also very long, adding to its impressive length .
Some sources claim that the Supersaurus was longer than its fellow sauropod, the Argentinosaurus, while others claim that it is about twenty feet shorter. Regardless of its exact length, the Supersaurus was undoubtedly one of the longest dinosaurs that existed. Even so, it weighed significantly less than other sauropods. Though the Barosaurus was once thought of as the closest relative of the Supersaurus, it is now thought that it has more in common with the Apatosaurus. Some paleontologists claim that the Ultrasauros, rather than having a category of its own, was actually a species of Supersaurus .
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Length: 120 feet
Height: 70 feet
Weight: 110 tons 
The Argentinosaurus, or “Argentina lizard,” was an herbivore and a quadruped that walked the Earth during the late Cretaceous period. As can be gathered from its name, this dinosaur was unearthed in Argentina only recently. Competing with the Seismosaurus for the title of the largest dinosaur that ever existed, the Argentinosaurus had astonishingly sized bones. One of the cross sections of its vertebra hovers at a height of five and one half feet.
Because of the immensity of the Argentinosaurus, some scientists classify it as a titanosaur. The entire skeleton of this dinosaur has not yet been uncovered. With size and weight estimates that are already mind-boggling, it is difficult to imagine the possibility that the Argentinosaurus may be even larger than already thought. Based on the location of its fossils, the Argentinosaurus was thought to have been hunted by a carnivorous theropod known as the Gigantosaurus. Both species were discovered within the vicinity of each other in South America .
Credit: Alain BeneteauCredit: Alain Beneteau
Length: 150 feet
Height: 84 feet
Weight: 100 tons 
The Seismosaurus (“earth-shaking lizard”) was an herbivore and a quadruped that lived during the late Jurassic period. This dinosaur is well-deserving of its top place on this list, namely because of its impressive length. The average American man stands 5 feet, 10 inches tall. It would take nearly 26 American men stacked on top of each other to equal the length of one Seismosaurus. Current research shows that it is the longest dinosaur that existed. This dinosaur was found in New Mexico and is thought to have used gastroliths in order to assist it in grinding its food for digestion .
There is much debate, not only about the size of the Seismosaurus, but also about its classification. Once thought to have belonged to its own genus, it is now thought that the Seismosaurus was a species of Diplodocus. Some scientists believe that this dinosaur was only about a quarter of the weight that previous paleontologists have estimated. They also disagree with the suggested length of the Seismosaurus. Despite certain scientific doubts, the Seismosaurus is still considered the longest dinosaur to have existed and thus tops the list of the 15 biggest dinosaurs that ever walked this earth .
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