ZPAL MgD-I/1 cast mount
Gallimimus bullatus • “Chicken mimic with capsule”
A fleet-footed ostrich-mimic theropod with a toothless keratinous beak suited for omnivorous grazing on vegetation, seeds, and small wetland invertebrates.
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.
Gallimimus bullatus lived during the Cretaceous, while Allosaurus fragilis inhabited the Jurassic. They were separated by roughly 74 million years of deep time and never encountered one another in the ancient world. Gallimimus bullatus was an adapted omnivore, whereas Allosaurus fragilis was a carnivore, representing fundamentally distinct ecological roles. Based on available fossil estimates, Allosaurus fragilis was larger than Gallimimus bullatus in both overall length and estimated body mass (approximately 4.44× heavier and 1.42× longer). Estimates vary between individual specimens.
Anatomical dimensions compared on a shared proportional baseline against an adult human (1.8 m / 5.9 ft).
Allosaurus fragilis was longer by approximately 2.5 m.
Allosaurus fragilis stood taller by approximately 1 m.
Allosaurus fragilis had a greater estimated mass by 1.6 tonnes.
Based on available fossil estimates, Allosaurus fragilis was larger than Gallimimus bullatus in both overall length and estimated body mass (approximately 4.44× heavier and 1.42× 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, Allosaurus fragilis was larger than Gallimimus bullatus in both overall length and estimated body mass (approximately 4.44× heavier and 1.42× longer). Estimates vary between individual specimens.
Gallimimus bullatus was an adapted omnivore, whereas Allosaurus fragilis was a carnivore, representing fundamentally distinct ecological roles.
Gallimimus bullatus lived during the Cretaceous (Late Cretaceous, 70 Ma), while Allosaurus fragilis lived during the Jurassic (Late Jurassic, 155–145 Ma).
Fossils of Gallimimus bullatus were recovered from Mongolia (Nemegt Basin), whereas Allosaurus fragilis was discovered in Western United States (Morrison Formation), Portugal.
Gallimimus bullatus had a bipedal locomotion, contrasted with Allosaurus fragilis which had a bipedal stance.
Gallimimus bullatus and Allosaurus fragilis did NOT live at the same time. They were separated by an immense temporal gulf of approximately 74 million years. Allosaurus fragilis lived and went extinct tens of millions of years before Gallimimus bullatus ever evolved.
Side-by-side catalog of verified anatomical measurements and geological records.
| Scientific Parameter | A Gallimimus bullatus | B Allosaurus fragilis |
|---|---|---|
| Scientific Binomial | Gallimimus bullatus | Allosaurus fragilis |
| Name Meaning | “Chicken mimic with capsule” | “Different lizard, fragile” |
| Taxonomic Clade / Group | Theropods | Theropods |
| Geological Period | Cretaceous | Jurassic |
| Fossil Time Range | Late Cretaceous, 70 Ma | Late Jurassic, 155–145 Ma |
| Diet & Trophic Guild | Omnivore | Carnivore |
| Maximum Length | 6 m (19.7 ft) | 8.5 m (27.9 ft) |
| Standing / Hip Height | 2 m (6.6 ft) | 3 m (9.8 ft) |
| Estimated Body Mass | 0.5 tonnes (450 kg) | 2 tonnes (2,000 kg) |
| Locomotion / Stance | Bipedal | Bipedal |
| Geographic Localities | Mongolia (Nemegt Basin) | Western United States (Morrison Formation), Portugal |
| Geological Formation | Nemegt Formation | Morrison Formation, Lourinhã Formation |
| Discovery History | Historical holotype | Historical holotype |
Visualizing both species across the 186-million-year span of the Mesozoic Era.
Gallimimus bullatus and Allosaurus fragilis did NOT live at the same time. They were separated by an immense temporal gulf of approximately 74 million years. Allosaurus fragilis lived and went extinct tens of millions of years before Gallimimus bullatus ever evolved.
Deep-time perspective: Gallimimus bullatus and Allosaurus fragilis were separated by approximately 74 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.
Mongolia (Nemegt Basin)
Asia
Western United States (Morrison Formation), Portugal
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.