The Brontosaurus, meaning “thunder lizard,” is one of the most recognized dinosaurs from the Late Jurassic period, roughly 150 million years ago. This gigantic herbivore belonged to the sauropod group, characterized by their immensely long necks, colossal bodies, and long tails. Its fossil remains, found primarily in the Morrison Formation of western North America, reveal an animal whose size was surpassed by only a few other known species. Understanding its full dimensions requires examining the history of its discovery and the scientific methods used to translate fragmented bones into a fully realized giant.
The Naming and Classification History
The scientific identity of this animal has been debated for over a century, stemming from the intense paleontological rivalries of the late 19th century. American paleontologist Othniel Charles Marsh first named the genus Brontosaurus in 1879 after discovering a nearly complete skeleton in Wyoming. Marsh had previously described a related specimen two years earlier under the name Apatosaurus.
The confusion peaked in 1903 when paleontologist Elmer Riggs concluded that the differences between Brontosaurus and Apatosaurus were not significant enough to warrant two separate genera. Following scientific nomenclature rules, the older name, Apatosaurus, took priority, and Brontosaurus was officially retired from the scientific lexicon. Despite this demotion, the name Brontosaurus persisted in popular culture and museum exhibits for decades.
The name was finally reinstated in 2015 after a comprehensive morphological analysis led by Emanuel Tschopp. This study examined skeletal characteristics across 81 specimens of the Diplodocidae family. The findings demonstrated that the skeletal differences, particularly in the robustness of the neck vertebrae, were substantial enough to validate Brontosaurus as a distinct genus once again. Brontosaurus specimens were found to have a more slender build compared to the heavier Apatosaurus.
Calculating the Full Dimensions
Paleontologists determine the overall size of Brontosaurus using complete skeletal remains, scaling techniques, and biomechanical models. The estimated total length of a fully grown Brontosaurus excelsus is approximately 69 to 75 feet (21 to 23 meters). This immense length is dominated by the neck and tail, with the tail alone making up more than half of the animal’s total span.
The overall body mass is estimated to have ranged between 15 and 20 metric tons (about 33,000 to 44,000 pounds), a weight comparable to several large modern vehicles. Determining the height involves two distinct measurements: hip height and maximum neck extension. The hip height, the distance from the ground to the top of its back, is estimated to have been around 15 feet (4.5 meters).
When the animal fully raised its neck to browse on high foliage, its head could reach a maximum height of approximately 28 feet (8.5 meters). This browsing height is calculated using models that consider the structure of the neck vertebrae and muscle strength. The robust neck vertebrae suggest it held its neck in a relatively straight line, allowing it to sweep a large area for food without moving its massive body.
A Full Scale Comparison
To grasp the magnitude of a Brontosaurus, its dimensions can be compared with familiar modern objects. At a length of up to 75 feet, a single Brontosaurus would be longer than two standard city buses parked end-to-end. This length is nearly equivalent to the width of a regulation tennis court, which measures about 78 feet.
The colossal mass of 15 to 20 tons equates to the weight of about four fully grown African bush elephants. Its massive torso was supported by stout, columnar limbs that distributed this incredible weight. The 15-foot height to its back would allow the animal to comfortably peer over a basketball hoop, which is only 10 feet tall.
Reaching its maximum browsing height of 28 feet, a Brontosaurus could look over the roof of a typical three-story house. Its immense size dictated its life, requiring it to consume hundreds of pounds of vegetation daily to maintain its bulk.