The history of life on Earth is marked by the rise and fall of countless species, with over 99% of all species that have ever existed now extinct. Humanity has long been captivated by the immense scale of ancient creatures that once roamed our planet. The fossil record offers glimpses into a time when giants walked, swam, and flew, providing insight into the extremes of biological evolution.
The Heaviest Known Extinct Animal
The title of the heaviest known extinct animal currently belongs to Perucetus colossus, an ancient whale that lived approximately 39 million years ago during the Eocene period in what is now Peru. Initial estimates suggested a body mass ranging from 85 to 340 metric tons, influenced by its unusually dense bones, a condition known as pachyostosis.
However, more recent research refined these estimations. Scientists now propose that Perucetus colossus likely weighed between 60 and 70 tons for an individual measuring 17 meters in length. Even an individual reaching 20 meters in length would probably weigh over 110 tons, still less than the largest blue whales.
For comparison, the blue whale (Balaenoptera musculus), the largest animal alive today, can reach a maximum length of 29.9 to 30.5 meters and weigh up to 190-200 tons. While Perucetus colossus was considerably shorter than a blue whale, its skeletal mass was remarkably high, two to three times heavier than a 25-meter blue whale skeleton.
Giants of Land and Sky
While Perucetus colossus represents an extreme in aquatic mass, other extinct animals dominated the land and sky with their immense proportions. On land, the sauropod dinosaurs reached unparalleled sizes. Argentinosaurus huinculensis is considered one of the largest known land animals, with estimates placing its length between 30 and 35 meters (98 to 115 feet) and its weight between 65 and 80 tons.
Another contender for the largest land animal is Patagotitan mayorum, a titanosaur discovered in Argentina. While initial reports suggested it was around 40 meters long and weighed 77 tons, more recent estimates have revised its size to approximately 31 meters in length and 50 to 57 tons in weight. This suggests it may have been of similar size to, or slightly smaller than, Argentinosaurus. Both roamed the Earth during the Late Cretaceous period.
In the skies, Quetzalcoatlus northropi holds the record as the largest known flying animal. This pterosaur, which lived during the Late Cretaceous, had a wingspan of up to 10 to 11 meters (33 to 36 feet), comparable to a small airplane. On the ground, it could reach a height of about 5 meters (16 feet), similar to a giraffe. Its hollow bones contributed to its ability to fly despite its large size.
How Scientists Estimate Size
Estimating the size of extinct animals relies on complex paleontological work, as direct measurement is impossible. Scientists primarily use fossilized skeletal remains to reconstruct an animal’s dimensions. This process often involves comparing the found bones to those of modern animals with known sizes, looking for correlations between bone dimensions (like limb bone circumference) and overall body mass.
Skeletal reconstruction is important, where paleontologists piece together fragmentary fossils, sometimes using digital 3D modeling to fill in missing parts or correct for distortions that occurred during fossilization. Once a skeletal framework is established, scientists estimate muscle and tissue mass. This involves techniques such as volumetric modeling, where contours representing soft tissues are sculpted around the skeleton, and density values are applied to calculate total body mass. These estimations involve a degree of uncertainty, especially when fossil records are incomplete or when the extinct animal has no close living relatives for direct comparison.