CMC VP 7180 mount
Allosaurus fragilis • “Different lizard, fragile”
The most common and lethal apex predator of the Late Jurassic Morrison Formation, hunting with gaping jaws, slashing bites, and robust three-clawed forelimbs.
FMNH PR 2081 ("Sue")
Tyrannosaurus rex • “Tyrant Lizard King”
Tyrannosaurus rex was one of the largest terrestrial carnivores of all time, roaming western North America just prior to the Cretaceous-Paleogene extinction event. With…
Allosaurus fragilis lived during the Jurassic, while Tyrannosaurus rex inhabited the Cretaceous. They were separated by roughly 77 million years of deep time and never encountered one another in the ancient world. Both species shared a carnivore diet, occupying comparable trophic levels in their respective food webs. Based on available fossil estimates, Tyrannosaurus rex was larger than Allosaurus fragilis in both overall length and estimated body mass (approximately 4.2× heavier and 1.45× longer). Estimates vary between individual specimens.
Anatomical dimensions compared on a shared proportional baseline against an adult human (1.8 m / 5.9 ft).
Tyrannosaurus rex was longer by approximately 3.8 m.
Tyrannosaurus rex stood taller by approximately 0.7 m.
Tyrannosaurus rex had a greater estimated mass by 6.4 tonnes.
Based on available fossil estimates, Tyrannosaurus rex was larger than Allosaurus fragilis in both overall length and estimated body mass (approximately 4.2× heavier and 1.45× 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, Tyrannosaurus rex was larger than Allosaurus fragilis in both overall length and estimated body mass (approximately 4.2× heavier and 1.45× longer). Estimates vary between individual specimens.
Both species shared a carnivore diet, occupying comparable trophic levels in their respective food webs.
Allosaurus fragilis lived during the Jurassic (Late Jurassic, 155–145 Ma), while Tyrannosaurus rex lived during the Cretaceous (Late Cretaceous, 68–66 Ma).
Fossils of Allosaurus fragilis were recovered from Western United States (Morrison Formation), Portugal, whereas Tyrannosaurus rex was discovered in Western North America (Montana, South Dakota, Wyoming, Alberta, Saskatchewan).
Allosaurus fragilis had a bipedal locomotion, contrasted with Tyrannosaurus rex which had a bipedal stance.
Allosaurus fragilis and Tyrannosaurus rex did NOT live at the same time. They were separated by an immense temporal gulf of approximately 77 million years. Allosaurus fragilis lived and went extinct tens of millions of years before Tyrannosaurus rex ever evolved.
Side-by-side catalog of verified anatomical measurements and geological records.
| Scientific Parameter | A Allosaurus fragilis | B Tyrannosaurus rex |
|---|---|---|
| Scientific Binomial | Allosaurus fragilis | Tyrannosaurus rex |
| Name Meaning | “Different lizard, fragile” | “Tyrant Lizard King” |
| Taxonomic Clade / Group | Theropods | Theropods |
| Geological Period | Jurassic | Cretaceous |
| Fossil Time Range | Late Jurassic, 155–145 Ma | Late Cretaceous, 68–66 Ma |
| Diet & Trophic Guild | Carnivore | Carnivore |
| Maximum Length | 8.5 m (27.9 ft) | 12.3 m (40.4 ft) |
| Standing / Hip Height | 3 m (9.8 ft) | 3.7 m (12.1 ft) |
| Estimated Body Mass | 2 tonnes (2,000 kg) | 8.4 tonnes (8,400 kg) |
| Locomotion / Stance | Bipedal | Bipedal |
| Geographic Localities | Western United States (Morrison Formation), Portugal | Western North America (Montana, South Dakota, Wyoming, Alberta, Saskatchewan) |
| Geological Formation | Morrison Formation, Lourinhã Formation | Hell Creek Formation, Lance Formation, Scollard Formation |
| Discovery History | Historical holotype | Barnum Brown (1902); described by Henry Fairfield Osborn (1905) (1902) |
Visualizing both species across the 186-million-year span of the Mesozoic Era.
Allosaurus fragilis and Tyrannosaurus rex did NOT live at the same time. They were separated by an immense temporal gulf of approximately 77 million years. Allosaurus fragilis lived and went extinct tens of millions of years before Tyrannosaurus rex ever evolved.
Deep-time perspective: Allosaurus fragilis and Tyrannosaurus rex were separated by approximately 77 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.
Western United States (Morrison Formation), Portugal
North America
Western North America (Montana, South Dakota, Wyoming, Alberta, Saskatchewan)
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.