Prehistoric Life Wiki

Big thanks to Concavenator Wrangler, DragonSaber73, H25a, and Theropod King for helping create this list.

10th - Dreadnoughtus
Complete Sauropods are always significant finds. Many of the most famous large Sauropods are only known from small portions of their skeletons. An example would be the Titanosaurian Sauropod Puertasaurus. Less than 2 percent of the animal has been recovered. Historically, these large Sauropods have been scaled to more complete, smaller Sauropod specimens. Dreadnoughtus is a good example of a complete Sauropod as more than 45 percent of the animal was recovered. Since some of the remains could be "reflected," as in left and right legs, more than 70 percent of the total animal can be put together accurately. What makes Dreadnoughtus stand out more is the fact that it is also a very large Sauropod. Current estimates indicate it's mass was just below 40 tonnes.
9th - Camarasaurus
Camarasaurus 1.jpg
Not only is Camarasaurus a relatively large Sauropod, it was also one of the more common in Late Jurassic North America. As such, it has been studied quite extensively. Evidence exists that Camarasaurus traveled in herds or small family groups.

It was also involved in the early Brontosaurus chimera as its head was placed onto the skeleton of Brontosaurus, partially leading to the assumption that the latter was an invalid taxon.

8th - Amargasaurus
Amargasaurus is most known for a series of bizarre spines that ran along the back of its neck. The use of these is not clear, but it has been suggested that they could be used to fend of predators. Turning the row toward an attacking animal would present a formidable obstacle.
7th - Europasaurus
Europasaurus is an example of a basal Macronarian, a group known for long necks and forelimbs which are longer than their hind limbs. Europasaurus exhibits a number of physiological differences from later members of its clade. It is also known from Germany, possibly living on a Jurassic Island. Therefore, it is seen as an example of insular dwarfism, meaning that its habitat could not support large individuals, resulting in smaller overall size. While this has been observed in some Sauropods, Europsasaurus is unique as it is the only Suaropodomorph, or, ancestor of the Sauropods, currently known to have declined in size as opposed to growing larger. Europasaurus is classified as both a Sauropod and a Sauropodomorph.
6th - Saltasaurus
Like Amargasaurus, Saltasaurus had an interesting defense mechanism. A series of bony scales, or "osteoderms", were present on its back. These would have made it very hard for predators to take down. A similar adaptation is seen in the European Titanosaur Ampelosaurus, and is believed by some to have been a more widespread trait among later Titanosaurs. Another significant discovery related to Saltasaurus is a nesting sight called "Auca Mahuevo," which countains a vast amount of Saltasaur nests preserved in a flood plain. 
5th - Shunosaurus
573px-Shunosaurus life restoration.jpg
Shunosaurus is most known for its bony "club" on the end of its tail. This was most likely used to fend off attacking predators, and would have been a formidable weapon when swung by a muscular Sauropod tail. Some other Jurassic Sauropods from Asia, including the large Mamenchisaurus, show evidence of a similar bony growth. Shunosaurus is also interesting due to the fact that it had a very short neck by Sauropod standards.
4th - Argentinosaurus
Today, Argentinosaurus is probably the most common dinosaur credited as being the "largest land animal of all time." It is only known from small amounts of material. Therefore, length estimates range from 27-40 meters, and mass estimates range from 50 tonnes to 110 tonnes. Today, size estimates are typically on the lower end of the spectrum. However, this still makes Argentinosaurus one of the largest land animals ever, and quite possibly the largest.
3rd - Brachiosaurus
1200px-Brachiosaurus size.png
Brachiosaurus is one of the most famous Sauropods. As a macronarian, it had a long neck and larger forelimbs than hind limbs. Due to its immense size, it would have probably been a high-level browser, meaning it would not have to compete with lower-level browsers such as Stegosaurs or smaller Sauropods. The skull of Brachiosaurus is also quite iconic, occasionally assigned to incorrect genera in popular media.
2nd - Apatosaurus
Apatosaurus is one of the earlier forms of Diplodocid Sauropod. It had numerous differences from other Diplodocids that indicate a uniquely robust build. It is also well known for the Brontosaurus debate. For over a hundred years, Brontosaurus was not seen as a valid taxon, but rather, a junior synonym for Apatosaurus. While they are now widely regarded as two separate genera, some paleontologists do not agree that they are indeed different.
1st - Diplodocus
1200px-Diplodocus carnegii.jpg
The top of this list is one of the most iconic of all dinosaurs. Diplodocus is represented by incredibly numerous remains of different individuals, allowing the animal to be reconstructed to a great degree of completeness. For a long time, Diplodocus was also the longest dinosaur known from reasonably complete remains. The large size of Diplodocus probably helped it fend off predators such as Allosaurus. It is also distinctive for its incredibly long tail, composed of around 80 vertebrae. Diplodocus is also the type genus of the family Diplodocidae.