While the Blue Whale holds the record for the largest animal in the planet’s history, the mechanical constraints of supporting immense weight outside of water mean the land-dwelling record belongs to a different group of giants. Pinpointing the absolute largest terrestrial animal involves navigating a complex scientific debate, as the evidence often consists of fragmented fossils rather than complete skeletons. Paleontologists must rely on sophisticated estimation methods, which sometimes leads to differing conclusions about which creature deserves the ultimate title.
The Reigning Record Holder
The current scientific consensus identifies the long-necked herbivore Patagotitan mayorum as the largest animal to have ever walked on land. This colossal dinosaur belongs to the group of sauropods known as titanosaurs, which dominated the landscape during the Cretaceous period.
Patagotitan reached approximately 37 meters (122 feet) in length. Its weight is estimated at 69 to 70 metric tons, roughly equivalent to the mass of a dozen adult African elephants. Its shoulder height was nearly 6 meters, with its head capable of reaching 14 meters (46 feet) high while fully raised.
The fossil remains of this species were discovered in 2012 and 2013 on a farm in the Chubut Province of Patagonia, Argentina. Patagotitan mayorum lived about 101.6 million years ago. The discovery included the remains of at least six individuals, making it one of the most complete titanosaurs known to science, which helps establish its size estimate with a higher degree of certainty compared to other fragmentary giants.
How Paleontologists Estimate Size and Mass
Determining the size of extinct giants is challenging because paleontologists rarely find a complete skeleton, forcing them to use indirect methods to calculate body mass.
One fundamental approach is limb bone scaling, often called allometry, which relies on the relationship between bone circumference and body mass in living animals. Researchers measure the circumference of weight-bearing bones, such as the femur and humerus, and use mathematical formulas to estimate the total body weight. This method is based on the principle that bone thickness must increase in proportion to the load it supports.
Another widely used technique is volumetric reconstruction, which involves creating a detailed three-dimensional model of the dinosaur’s body. This process begins with an accurate skeletal reconstruction, followed by the addition of soft tissues, such as muscle, fat, and skin, digitally or through scale models. The determined volume is then multiplied by an estimated average density for a living animal (e.g., 0.9 to 1.0 kg per liter) to arrive at a total mass.
These methods are often used together to provide a range of likely body mass, but results vary based on assumptions about soft tissue and internal air sacs. For instance, the presence of extensive air sacs, common in sauropods, would lower the overall body density and the final weight estimate. When only fragmentary remains are available, scientists must scale up the known bones using the proportions of more complete, related species, which introduces a greater margin of error.
Rivals to the Title: Other Terrestrial Giants
While Patagotitan currently holds the record, other colossal sauropods from Patagonia are close contenders, underscoring the ongoing scientific debate. Argentinosaurus huinculensis, the previous record holder, is estimated to have been slightly longer, reaching up to 40 meters (131 feet), with a mass between 65 and 80 metric tons. However, the fossil record for Argentinosaurus is more fragmented than that of Patagotitan, contributing to the wider range of its size estimates.
Other immense titanosaurs, such as Dreadnoughtus and Puertasaurus, also boast comparable bulk. Dreadnoughtus is known from a relatively complete specimen with a mass estimated at roughly 65 tons, making it one of the most reliably sized mega-sauropods. These animals all belong to a lineage of super-sized sauropods that evolved in South America during the Cretaceous.
Compared to these dinosaurs, the largest known terrestrial mammal, Paraceratherium, appears significantly smaller. This extinct hornless rhinoceros relative, which lived about 34 to 23 million years ago, is estimated to have weighed between 11 and 20 metric tons. For scale, the largest living land animal today, the African Bush Elephant, typically weighs an average of around six metric tons.