Defining “biggest” is key to identifying the largest creature, as size can be measured by length, mass, or volume. Different metrics can lead to different organisms holding the record. This article explores the largest known creatures across Earth’s history, considering these different measurements.
The Blue Whale: Earth’s Largest Animal
The blue whale (Balaenoptera musculus) is the largest animal known to have ever existed, both currently and historically, in terms of both mass and length. An adult blue whale can reach a maximum confirmed length of 29.9 to 30.5 meters (98 to 100 feet) and weigh up to 190 to 199 metric tons (209 to 219 short tons). Some individuals have been recorded at over 33 meters (108 feet) in length and weighing more than 150,000 kilograms (330,000 pounds). To visualize its size, a blue whale can be as long as three school buses, and its heart is comparable in size to a small car, weighing around 180 kg (400 pounds).
These marine mammals possess a long, streamlined body. Their size is supported by the buoyancy of water, reducing the effects of gravity that land animals face. Blue whales are baleen whales, filter-feeding on vast quantities of krill. Some large individuals can eat up to 6 tons of krill per day. Newborn calves are substantial, measuring about 7 meters (23 feet) long and weighing 2,268 to 2,722 kilograms (5,000 to 6,000 pounds) at birth, gaining weight rapidly, sometimes up to 4.5 kilograms (10 pounds) per hour.
Titans of the Past: Prehistoric Giants
While the blue whale is the largest animal, prehistoric eras featured other colossal creatures. Sauropod dinosaurs, with their long necks and massive bodies, were among the largest land animals. Argentinosaurus, a titanosaurian sauropod from the Late Cretaceous period, is considered one of the largest known land animals. Estimates suggest a length of 30 to 35 meters (98 to 115 feet) and a weight of 65 to 80 metric tons (72 to 88 short tons). Its fragmentary fossil record means size estimates vary, but it remains a contender for the heaviest land animal.
Another titanosaur, Patagotitan mayorum, was discovered in Argentina. Initial estimates suggested a length of 37 meters (121 feet) and a weight of 69 metric tons (76 short tons). Later research revised these to 31 meters (102 feet) and 50 to 57 metric tons (55 to 63 short tons). While its exact size is debated due to incomplete fossil remains, Patagotitan is among the largest dinosaurs, with a thigh bone measuring 2.38 meters (7.8 feet) long.
In ancient oceans, the Megalodon (Otodus megalodon) was an apex predator from 23 to 3.6 million years ago. This shark is estimated to have reached lengths of 15 to 20 meters (50 to 65 feet), and weighed between 50 and 70 metric tons (55 to 77 short tons). Its teeth, up to 17.8 cm (7 inches) long, provide evidence for its size. On land, the hornless rhinoceros Paraceratherium was one of the largest terrestrial mammals, living approximately 34 to 23 million years ago. Estimates suggest a shoulder height of 4.8 meters (15.7 feet) and a length of 7.4 meters (24.3 feet), with weights from 15 to 20 metric tons (33,000 to 44,000 pounds).
Beyond Animals: The Largest Organisms
Beyond animals, the largest organisms include plants and fungi, where size can be measured by mass, area, or volume. Among plants, the General Sherman Tree, a giant sequoia (Sequoiadendron giganteum) in California’s Sequoia National Park, is the largest single-stem tree by volume. This tree measures 83 meters (272.4 feet) tall and has a circumference of 31 meters (101.5 feet) at its base, with an estimated total weight of 6,167 metric tons. While not the tallest, its trunk volume, estimated at 1,489 cubic meters (52,600 cubic feet), is unparalleled.
Clonal colonies represent some of the largest organisms by mass and area. Pando, a clonal colony of quaking aspen (Populus tremuloides) in Utah, is considered the world’s most massive single organism. Though it appears as a grove of many trees, Pando is genetically one individual connected by an extensive root system, spanning approximately 43 hectares (106 acres).
In the fungal kingdom, Armillaria ostoyae, known as the “Humongous Fungus,” holds the record for the largest organism by area. A specimen in Oregon’s Malheur National Forest covers 8.9 square kilometers (3.5 square miles), or about 2,200 acres. This single fungal colony, primarily growing underground as a network of mycelia, is estimated to weigh 35,000 metric tons and could be thousands of years old. It grows by feeding on tree roots.
Unraveling Gigantism: How Size is Determined
Scientists use various methods to determine the size of creatures, both living and extinct. For living animals, direct measurement involves weighing and measuring length. Weighing massive creatures like whales presents logistical challenges, often requiring specialized equipment and careful handling to ensure animal safety and accurate readings.
Determining the size of extinct species from fossil remains is more complex, involving indirect methods. Paleontologists rely on fossil analysis, comparing discovered bones to those of closely related living animals. For creatures without close living relatives, scientists use volumetric 3D modeling. This involves reconstructing a skeletal model, calculating its volume, and applying an estimated tissue density to derive a mass.
Other methods include analyzing limb bones, which indicate the weight an animal could bear. Muscle attachment points on bones also provide clues about muscle size. These estimations have inherent difficulties, such as incomplete fossil records. Fragmentation can lead to a range of size estimates for the same species, as different reconstruction methods or assumptions about missing parts can influence the final figures. Ongoing research refines these methods, providing increasingly accurate insights into the scale of Earth’s giants.