FMNH P 25107 mount
Brachiosaurus altithorax • “Arm lizard with high chest”
A colossal macronarian sauropod with disproportionately long forelimbs and an elevated neck built for high-canopy conifer browsing during the Late Jurassic.
AMNH 5214 / AMNH 5895 skull cast
Ankylosaurus magniventris • “Fused lizard with great belly”
The living tank of the Late Cretaceous, armored in thick osteoderm plates with cranial horns and a massive distal tail club capable of shattering…
Brachiosaurus altithorax lived during the Jurassic, while Ankylosaurus magniventris inhabited the Cretaceous. They were separated by roughly 82 million years of deep time and never encountered one another in the ancient world. Both species shared a herbivore diet, occupying comparable trophic levels in their respective food webs. Based on available fossil estimates, Brachiosaurus altithorax was larger than Ankylosaurus magniventris in both overall length and estimated body mass (approximately 5.83× heavier and 3.25× longer). Estimates vary between individual specimens.
Anatomical dimensions compared on a shared proportional baseline against an adult human (1.8 m / 5.9 ft).
Brachiosaurus altithorax was longer by approximately 18 m.
Brachiosaurus altithorax stood taller by approximately 10.3 m.
Brachiosaurus altithorax had a greater estimated mass by 29 tonnes.
Based on available fossil estimates, Brachiosaurus altithorax was larger than Ankylosaurus magniventris in both overall length and estimated body mass (approximately 5.83× heavier and 3.25× longer). Estimates vary between individual specimens.
Paleontological Note on Mass Estimates: Dinosaur body weights are derived through volumetric laser scanning and femoral circumference scaling equations. Because soft tissue does not fossilize directly, mass values carry statistical margins of uncertainty and represent scientific estimates rather than exact weights.
Direct answers to the most important comparative questions about how these two prehistoric species differed.
Based on available fossil estimates, Brachiosaurus altithorax was larger than Ankylosaurus magniventris in both overall length and estimated body mass (approximately 5.83× heavier and 3.25× longer). Estimates vary between individual specimens.
Both species shared a herbivore diet, occupying comparable trophic levels in their respective food webs.
Brachiosaurus altithorax lived during the Jurassic (Late Jurassic, 154–150 Ma), while Ankylosaurus magniventris lived during the Cretaceous (Late Cretaceous, 68–66 Ma).
Fossils of Brachiosaurus altithorax were recovered from Colorado, Utah, Wyoming (Morrison Formation), whereas Ankylosaurus magniventris was discovered in Montana, Wyoming, Alberta.
Brachiosaurus altithorax had a quadrupedal locomotion, contrasted with Ankylosaurus magniventris which had a quadrupedal stance.
Brachiosaurus altithorax and Ankylosaurus magniventris did NOT live at the same time. They were separated by an immense temporal gulf of approximately 82 million years. Brachiosaurus altithorax lived and went extinct tens of millions of years before Ankylosaurus magniventris ever evolved.
Side-by-side catalog of verified anatomical measurements and geological records.
| Scientific Parameter | A Brachiosaurus altithorax | B Ankylosaurus magniventris |
|---|---|---|
| Scientific Binomial | Brachiosaurus altithorax | Ankylosaurus magniventris |
| Name Meaning | “Arm lizard with high chest” | “Fused lizard with great belly” |
| Taxonomic Clade / Group | Sauropods | Ankylosaurs |
| Geological Period | Jurassic | Cretaceous |
| Fossil Time Range | Late Jurassic, 154–150 Ma | Late Cretaceous, 68–66 Ma |
| Diet & Trophic Guild | Herbivore | Herbivore |
| Maximum Length | 26 m (85.3 ft) | 8 m (26.2 ft) |
| Standing / Hip Height | 12 m (39.4 ft) | 1.7 m (5.6 ft) |
| Estimated Body Mass | 35 tonnes (35,000 kg) | 6 tonnes (6,000 kg) |
| Locomotion / Stance | Quadrupedal | Quadrupedal |
| Geographic Localities | Colorado, Utah, Wyoming (Morrison Formation) | Montana, Wyoming, Alberta |
| Geological Formation | Morrison Formation | Hell Creek & Scollard Formations |
| Discovery History | Historical holotype | Historical holotype |
Visualizing both species across the 186-million-year span of the Mesozoic Era.
Brachiosaurus altithorax and Ankylosaurus magniventris did NOT live at the same time. They were separated by an immense temporal gulf of approximately 82 million years. Brachiosaurus altithorax lived and went extinct tens of millions of years before Ankylosaurus magniventris ever evolved.
Deep-time perspective: Brachiosaurus altithorax and Ankylosaurus magniventris were separated by approximately 82 million years. A visitor encountering one would have had no concept of the other.
Comparing the rock strata, paleoclimates, and ancient landscapes where their fossils were entombed.
Colorado, Utah, Wyoming (Morrison Formation)
North America
Montana, Wyoming, Alberta
North America
Stratigraphic Synthesis:
Direct comparisons between extinct animals are inherently shaped by the incomplete nature of the fossil record. Skeletal dimensions reflect holotype or well-preserved paratype specimens, but individual ontogenetic age, sexual dimorphism, and intraspecific variation all influence the true living size of any prehistoric animal.
Body mass estimates shown above represent calculated averages from published volumetric models and biomechanical limb scaling. As modern synchrotron imaging and 3D digital skeletal mounts advance, museum measurements are continually refined.