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.
MSNM V4047 / FSAC-KK 11888 digital skeletal cast mount
Spinosaurus aegyptiacus • “Spine lizard of Egypt”
A colossal semi-aquatic predatory theropod equipped with a massive dorsal neural sail, crocodyliform snout, and paddle-like tail adapted for pursuing giant Cretaceous fish.
Allosaurus fragilis lived during the Jurassic, while Spinosaurus aegyptiacus inhabited the Cretaceous. They were separated by roughly 46 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, Spinosaurus aegyptiacus was larger than Allosaurus fragilis in both overall length and estimated body mass (approximately 3.75× heavier and 1.76× longer). Estimates vary between individual specimens.
Anatomical dimensions compared on a shared proportional baseline against an adult human (1.8 m / 5.9 ft).
Spinosaurus aegyptiacus was longer by approximately 6.5 m.
Spinosaurus aegyptiacus stood taller by approximately 1.5 m.
Spinosaurus aegyptiacus had a greater estimated mass by 5.5 tonnes.
Based on available fossil estimates, Spinosaurus aegyptiacus was larger than Allosaurus fragilis in both overall length and estimated body mass (approximately 3.75× heavier and 1.76× 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, Spinosaurus aegyptiacus was larger than Allosaurus fragilis in both overall length and estimated body mass (approximately 3.75× heavier and 1.76× 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 Spinosaurus aegyptiacus lived during the Cretaceous (Late Cretaceous, 99–93 Ma).
Fossils of Allosaurus fragilis were recovered from Western United States (Morrison Formation), Portugal, whereas Spinosaurus aegyptiacus was discovered in Egypt, Morocco (Kem Kem Beds).
Allosaurus fragilis had a bipedal locomotion, contrasted with Spinosaurus aegyptiacus which had a bipedal / semi-aquatic stance.
Allosaurus fragilis and Spinosaurus aegyptiacus did NOT live at the same time. They were separated by an immense temporal gulf of approximately 46 million years. Allosaurus fragilis lived and went extinct tens of millions of years before Spinosaurus aegyptiacus ever evolved.
Side-by-side catalog of verified anatomical measurements and geological records.
| Scientific Parameter | A Allosaurus fragilis | B Spinosaurus aegyptiacus |
|---|---|---|
| Scientific Binomial | Allosaurus fragilis | Spinosaurus aegyptiacus |
| Name Meaning | “Different lizard, fragile” | “Spine lizard of Egypt” |
| Taxonomic Clade / Group | Theropods | Theropods |
| Geological Period | Jurassic | Cretaceous |
| Fossil Time Range | Late Jurassic, 155–145 Ma | Late Cretaceous, 99–93 Ma |
| Diet & Trophic Guild | Carnivore | Carnivore |
| Maximum Length | 8.5 m (27.9 ft) | 15 m (49.2 ft) |
| Standing / Hip Height | 3 m (9.8 ft) | 4.5 m (14.8 ft) |
| Estimated Body Mass | 2 tonnes (2,000 kg) | 7.5 tonnes (7,500 kg) |
| Locomotion / Stance | Bipedal | Bipedal / Semi-aquatic |
| Geographic Localities | Western United States (Morrison Formation), Portugal | Egypt, Morocco (Kem Kem Beds) |
| Geological Formation | Morrison Formation, Lourinhã Formation | Bahariya Formation, Kem Kem Beds |
| Discovery History | Historical holotype | Historical holotype |
Visualizing both species across the 186-million-year span of the Mesozoic Era.
Allosaurus fragilis and Spinosaurus aegyptiacus did NOT live at the same time. They were separated by an immense temporal gulf of approximately 46 million years. Allosaurus fragilis lived and went extinct tens of millions of years before Spinosaurus aegyptiacus ever evolved.
Deep-time perspective: Allosaurus fragilis and Spinosaurus aegyptiacus were separated by approximately 46 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
Egypt, Morocco (Kem Kem Beds)
Africa
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.