05Mesozoic
Tyrannosaurus
Tyrannosaurus rex
A deep skull, bone-crushing bite and keen senses made it one of the last giant theropods.
Western North America
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Dinosaurs of the United States
Explore US dinosaur fossils and continue into Texas and Montana, comparing Jurassic Morrison animals with younger Cretaceous records.
Places, environments and evidence
Morrison deposits preserve animals such as Allosaurus, Stegosaurus and Diplodocus; Hell Creek documents a later world including Tyrannosaurus and Triceratops. The Texas and Montana guides go one step further by requiring evidence tied to that state. Fossil-site location is distinct from the museum where a specimen is displayed.
06Mesozoic
Triceratops
Triceratops horridus
Three horns and a broad frill formed a formidable display and defense system.
Western North America
07Mesozoic
Stegosaurus
Stegosaurus stenops
Tall back plates and a four-spiked tail made this low-browsing herbivore unmistakable.
Western North America
10Mesozoic
Ankylosaurus
Ankylosaurus magniventris
Body armor and a heavy tail club turned a plant-eater into a walking fortress.
Western North America
40Mesozoic
Allosaurus
Allosaurus fragilis
A lightweight skull and serrated teeth equipped this large predator for repeated slashing bites.
Western North America
41Mesozoic
Brachiosaurus
Brachiosaurus altithorax
Long forelimbs lifted its shoulders and neck toward the Jurassic canopy.
Western North America
42Mesozoic
Diplodocus
Diplodocus carnegii
A whip-like tail balanced an extremely long neck on this lightly built giant.
Western North America
45Mesozoic
Deinonychus
Deinonychus antirrhopus
A stiff tail, grasping hands and enlarged foot claw made an agile feathered hunter.
Western North America
107Mesozoic
Utahraptor
Utahraptor ostrommaysorum
This huge, robust dromaeosaur used strength and a curved second-toe claw to control prey.
Western North America · Present-day Utah
224Mesozoic
Acrocanthosaurus
Acrocanthosaurus atokensis
Tall neural spines along the neck and back supported a muscular ridge rather than a paper-thin sail.
River plains and open woodland · North America
228Mesozoic
Kosmoceratops
Kosmoceratops richardsoni
Fifteen horn-like ornaments across the nose, brows and broad frill formed a folded crown around the skull.
Island coastal plain · Utah, USA
279Mesozoic
Sauropelta
Sauropelta edwardsorum
Long shoulder spikes and dense armor protected one of the largest nodosaurids.
River forests and open plains · North America
458Mesozoic
Nanuqsaurus
Nanuqsaurus hoglundi
It hunted through polar night, though its supposedly dwarf size remains uncertain.
High-latitude forest · Alaska
Common questions
Does every US dinosaur belong on the Montana page?
No. State guides use independently supported local occurrences. A general US or North American distribution is insufficient.