What Was the Biggest Dinosaur? Here Are the 4 Best Estimates

Argentinosaurus huinculensis is one of the largest dinosaurs ever discovered, and possibly the largest to have ever existed. It gets its name from the city where its fossilized bones were found: Plaza Huincul, Argentina.

Argentinosaurus was a titanosaur (not to be confused with the titanoboa), a group of giant sauropods that hold the title of the world's largest land animals and lived during the late Cretaceous period. Titanosaurs were plant-eaters and used their long necks to graze.

Size estimates place Argentinosaurus at 77 to 110 tons (70 to 100 metric tons) in weight and 121 to 131 feet (37 to 40 meters) in length. However, these estimates are based on just a few bones and may be inaccurate.

You can see Argentinosaurus' reconstructed skeleton at the Fernbank Museum of Natural History in Atlanta, Georgia.

Sauroposeidon proteles is possibly the tallest dinosaur, at an estimated 59 feet (18 meters) tall.

Discovered in Oklahoma in 1994, Sauroposeidon has the largest known neck vertebrae at 5 feet (1.5 meters) long. "It looked like a trunk of a tree," paleontologist Richard Cifelli told CBS News in 1999.

At the time of its discovery, some dinosaur enthusiasts thought Sauroposeidon, which lived in the early Cretaceous period, might be the world's largest dinosaur. Today, most scientists agree that, while Sauroposeidon is probably the world's tallest dinosaur, there are heavier and larger dinosaurs.

With only a few Sauroposeidon bones discovered, it's hard to know for sure.

You can see a reconstruction of Sauroposeidon's head and neck at the Sam Noble Museum in Oklahoma.

Named in 2017, Patagotitan mayorum, discovered in Patagonia, is the newest contender for largest dinosaur. It is estimated to have weighed 77 tons (70 metric tons), stood around 28 feet (8.5 meters) high at the head and was 122 feet (37.2 meters) long, and more of its bones have been found than Argentinosaurus and Sauroposeidon.

However, without a complete skeleton, it's hard to know the exact size of Patagotitan mayorum. You can see a complete reconstructed skeleton of Patagotitan mayorum at the American Museum of Natural History.

In 2014, Drexel University scientists discovered the 70-percent-complete skeleton of Dreadnoughtus schrani, "the largest land animal for which a body mass can be accurately calculated" at 85 feet long (26 meters) and weighing 65 tons (59 metric tons).

For comparison, the largest living land animal today is the African elephant. The largest animal to ever live is the blue whale (Balaenoptera musculus), which weighs 150 tons (136 metric tons) and is 98 feet (30 meters) long.

"Shockingly, skeletal evidence shows that when this 65-ton specimen died, it was not yet full grown," Kenneth Lacovara, PhD, the lead scientist in the discovery, said in a press release. "It is by far the best example we have of any of the most giant creatures to ever walk the planet."