With its iconic skull "hornlets," Allosaurus struck a unique and intimidating figure when compared to other carnivorous dinosaurs. This bipedal predator lived during the Late Jurassic, over 145,000,000 years ago, and used its powerful bite to take down prey in packs.
This specimen is a fragment of an Allosaurus vertebra recovered on private land from the Morrison Formation in Utah. Both small and medium fossil fragments are available in one of our handsome display cases.
📸 An artist's depiction of the Allosaurus
A Frightening Carnivore
Allosaurus was one of the most dominant predators of the Late Jurassic Period. Reaching 30ft (9m) in length, this large theropod is known for its powerful, three-fingered forelimbs, wide gape, and iconic "hornlets" over the eyes.
Named the state fossil of Utah in 1988, Allosaurus is one of the most plentiful dinosaurs found in Utah's bonebeds, including the Cleveland-Lloyd Dinosaur Quarry which holds the remains of nearly 50 individual juveniles and subadults.
📸 An example of a Medium Allosaurus vertebra specimen.
This specimen is a fragment of an Allosaurus vertebra recovered on private land from the Morrison Formation in Utah. Both small and medium sized vertebra fragments are available.
Classic Riker Box (Small) - Typically, 4-5mm, this is the classic Mini Museum specimen size found in our larger collections. The specimen is encased inside an acrylic specimen jar and can be removed for study.
Classic Riker Box (Medium) - Sizes and shapes vary widely on this specimen but they are roughly 0.75" (~2cm-3cm) in length.
Small and Medium Allosaurus vertebra specimens ship in our glass-topped riker display cases. The case measures 4"x3"x1". A small information card is also included, which also serves as the certificate of authenticity.
"This genus may be distinguished from any known Dinosaurs by the vertebrae, which are peculiarly modified to ensure lightness."~ Othniel Charles Marsh (1877)
MORE ABOUT Allosaurus
📸 Pathologies discovered in a single Allosaurus. Highlight on damage to the humerus. Foth (2015)
A pack hunter
Allosaurus appears to have been a hunter of good-sized prey. There are numerous instances of Allosaurus bite marks on Stegosaurus neck plates, and like many predators of today, Allosaurus fossil remains also show evidence of injury related to active hunting of larger animals. There is even one instance of an Allosaurus receiving a lethal puncture from a Stegosaurus tail spike!
All this evidence leads some scientists to theorize that Allosaurus might have hunted in groups, though the presence of multiple Allosaurus specimens in proximity to sauropods at mass kill sites may simply represent solitary individuals brought together by a common food source.
📸 Artist's concept of a living Allosaurus.
The unique skull of Allosaurus has fueled vigorous speculation as to the carnosaur's feeding ecology. Estimates for the bite force of Allosaurus are quite modest at 2,000 N, paling in comparison to the monstrous bite of Tyrannosaurus rex.
The teeth of its upper jaw (maxilla), which is significantly more robust than the lower jaw (mandible), are smaller than expected for such a hefty theropod. Yet the Allosaurus skull was exceedingly strong, reinforced with strut-like bones that helped alleviate stress. The structure of its skull and reduced jaw muscles, furthermore, apparently gave Allosaurus an impressively large gape.
📸 Allosaurus on display in Guyot Hall at Princeton University. Taken in 2019 during our visit with Dr. Gerta Keller for the Deccan Traps specimen, part of Death of the Dinosaurs.
Small Teeth — Scary Bite
The combination of its "overbuilt" skull, wide gape, and powerful neck muscles—which inserted into a transverse crest in back of the Allosaurus skull, a feature also found in tyrannosaurids—suggest Allosaurus didn't require a titanic bite to take out its prey.
Based on the Allosaurus skull's ultra-strong structure, the more massive upper versus lower jaw, and the beefy neck musculature, one hypothesis suggests Allosaurus may have attacked prey with a high-impact, "slash-and-tear" wallop of the maxilla, likened to a hatchet strike. An alternative idea proposes Allosaurus employed a more "conventional" muscle-powered bite, using its tremendous gape to seize the flesh of large animals—the relatively small teeth allowing a greater vertical bite radius—and a downward neck thrust to amplify impaling force.
Front of the Specimen Card
Back of the Specimen Card
Marsh, Othniel Charles. "ART. LIII.--Notice of New Dinosaurian Reptiles from the Jurassic formation." American Journal of Science and Arts (1820-1879) 14.84 (1877): 514.
Peterson, Joseph E., et al. "New data towards the development of a comprehensive taphonomic framework for the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, Central Utah." PeerJ 5 (2017): e3368.
Rayfield, E. J. "Aspects of comparative cranial mechanics in the theropod dinosaurs Coelophysis, Allosaurus and Tyrannosaurus." Zoological Journal of the Linnean Society 144.3 (2005): 309-316.
Bybee, Paul J., Andrew H. Lee, and Ellen-Thérèse Lamm. "Sizing the Jurassic theropod dinosaur Allosaurus: assessing growth strategy and evolution of ontogenetic scaling of limbs." Journal of Morphology 267.3 (2006): 347-359.Erickson, Gregory M. "The bite of Allosaurus." Nature 409.6823 (2001): 987.
Foth, Christian, et al. "New insights into the lifestyle of Allosaurus (Dinosauria: Theropoda) based on another specimen with multiple pathologies." PeerJ 3 (2015): e940.
Carpenter, Kenneth, et al. "Evidence for predator-prey relationships: examples for Allosaurus and Stegosaurus." The carnivorous dinosaurs (2005): 325-350.