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Tyrannosaur Distribution: Laramidia and Asia

Although T. rex is the most famous tyrannosaur, it was not the only one. Several different tyrannosaurs lived during the Late Cretaceous, especially in western North America and Asia. In North America, the most important region was Laramidia, the western island continent separated from eastern North America by the Western Interior Seaway.

Why are tyrannosaurs mostly found in Laramidia and Asia?

Late Cretaceous tyrannosaurids are best known from western North America and Asia. These regions were periodically connected by northern land routes, allowing dinosaur faunas to move between the continents. This helps explain why North American tyrannosaurs such as T. rex and Asian tyrannosaurs such as Tarbosaurus share so many similarities.

Other continents were more isolated during much of the Late Cretaceous. Europe was a series of islands, South America and Africa were separated by broad oceans, and Australia and Antarctica were far from the main tyrannosaur centers. This geographic isolation helps explain why giant tyrannosaurids are not found worldwide.

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Types of Tyrannosaur Dinosaurs

Tyrannosaurs belong within the coelurosaurian branch of theropod dinosaurs, the same broad group that also includes many feathered dinosaurs and the lineage that eventually led to birds. Early tyrannosauroids were generally smaller and more lightly built. Over time, some lineages evolved the massive skulls, bone-crushing teeth, and reduced arms seen in later tyrannosaurids.

The tyrannosaur fossil record shows tremendous diversity. Some species were adapted to warm southern environments, others lived in northern polar regions, and some Asian species looked remarkably similar to T. rex. The group continued evolving until the end-Cretaceous mass extinction brought their reign to an abrupt end.

Click on a tyrannosaur name below to jump to that section, or simply scroll down.

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Tyrannosaurs of Laramidia

Lythronax argestes — The Southern King of Gore — South Laramidia — 80 Mya

At about 80 million years old, Lythronax argestes is one of the oldest known large tyrannosaurids. Its fossils come from Grand Staircase-Escalante National Monument in Utah, which was part of southern Laramidia during the Late Cretaceous.

Although smaller than T. rex, Lythronax already had many classic tyrannosaur traits, including a short, wide skull, robust teeth, forward-facing eyes, and reduced arms. This shows that several important tyrannosaur features evolved earlier than the final appearance of Tyrannosaurus rex.

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Daspletosaurus torosus — Muscular Frightful Lizard — North Laramidia — 76 Mya

Daspletosaurus torosus lived about 77 to 74 million years ago in northern Laramidia. It grew to roughly 30 feet in length and had a large skull, strong jaws, and small crests above the eyes.

This tyrannosaur lived alongside another large predator, Gorgosaurus. Having two large carnivorous theropods in the same region is unusual, and paleontologists have suggested they may have occupied different ecological niches or had partially separated geographic ranges.

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Teratophoneus curriei — Monster Murderer — South Laramidia — 75 Mya

While Daspletosaurus lived in northern Laramidia, Teratophoneus curriei lived farther south in what is now Utah. Its fossils come from the Kaiparowits Formation, which is about 76 to 74 million years old.

Teratophoneus was smaller than the giant tyrannosaurs that came later, and its skull was comparatively short. Differences between southern and northern tyrannosaurs suggest that Laramidia may have had regional dinosaur communities separated by geography, sea-level changes, or mountain-building events.

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Bistahieversor sealeyi — The Bistahi Destroyer — South Laramidia — 74 Mya

Bistahieversor sealeyi lived about 74 million years ago in what is now New Mexico. At roughly 28 feet long, it was smaller than T. rex but was one of the top predators of southern Laramidia at the time.

This tyrannosaur had several distinctive skull features, including an additional opening above the eye socket, a keel along the lower jaw, and a specialized jaw joint. These features show that southern Laramidian tyrannosaurs were evolving their own regional forms before the later rise of Tyrannosaurus rex.

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Nanotyrannus lancensis — Dwarf Tyrant — Laramidia — 67 to 66 Mya

Nanotyrannus lancensis has long been controversial. For decades, many paleontologists debated whether it was a separate tyrannosaur or simply a juvenile Tyrannosaurus rex. Recent research on the famous Dueling Dinosaurs specimen supports Nanotyrannus as a distinct, fully grown tyrannosaur rather than a teenage T. rex.

Compared to T. rex, Nanotyrannus was smaller, more lightly built, and more agile, with proportionally longer arms and a higher tooth count. If these interpretations continue to hold, the end of the Cretaceous was more ecologically complex than once thought, with multiple tyrannosaur predators sharing the same ecosystems.

For more detail, see the main T. rex page section on Nanotyrannus vs. juvenile T. rex.

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Tyrannosaurus rex — Tyrant Lizard King — Laramidia — 67 to 66 Mya

Reaching lengths of more than 40 feet, Tyrannosaurus rex was the largest and most famous of the tyrannosaurs. It represents the peak of the giant tyrannosaur body plan: a massive skull, bone-crushing jaws, forward-facing eyes, powerful hind limbs, and reduced but muscular arms.

T. rex lived across Laramidia near the very end of the Cretaceous. Fossils are found from Canada through the western United States, including famous formations such as the Hell Creek and Lance formations. For a complete guide, visit the main Tyrannosaurus rex page.

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Nanuqsaurus hoglundi — Polar Bear Lizard — Polar Laramidia — 69 Mya

Nanuqsaurus hoglundi is a polar tyrannosaur from the Prince Creek Formation of northern Alaska. Its name comes from “nanuq,” an Iñupiat word for polar bear. The fossils are about 69 million years old and represent one of the most northern tyrannosaurs known.

This animal was smaller than an average T. rex. Its reduced size may reflect adaptation to a high-latitude environment with long winter darkness and seasonal food stress. The discovery of Nanuqsaurus shows that tyrannosaurs were able to thrive in a wide range of Late Cretaceous environments, including polar regions.

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Tyrannosaurs of Asia

Tarbosaurus bataar — Alarming Lizard Hero — Asia — 70 Mya

Tarbosaurus bataar was the giant tyrannosaur of Mongolia and China. It looked very similar to T. rex and reached comparable size, though its skull was generally narrower and its arms were even shorter.

At the end of the Cretaceous, Tarbosaurus was the apex predator of its Asian ecosystems, while T. rex filled a similar role in Laramidia. Juvenile, subadult, and adult Tarbosaurus specimens have helped paleontologists better understand how large tyrannosaurs changed as they grew.

Video showing the growth series of Tarbosaurus, a close relative of T. rex.

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Yutyrannus huali — Feathered Tyrant — Asia — 124 Mya

Yutyrannus huali was not a late giant tyrannosaurid like T. rex, but it is an important early tyrannosauroid. It lived about 124 million years ago in China and is famous because fossils preserve feather impressions.

At nearly 30 feet long, Yutyrannus is among the largest theropods known with direct evidence of feathers or feather-like filaments. These structures may have helped with insulation in a cooler Early Cretaceous climate. However, this does not prove that adult T. rex was feathered, because later tyrannosaur skin impressions show scales in the areas where feathers might otherwise be expected.

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Zhuchengtyrannus magnus — Great Tyrant of Zhucheng — Asia — 74 Mya

Zhuchengtyrannus magnus is a large tyrannosaur from China dating to about 73 to 74 million years ago. It is known from jaw material found at the Zangjiazhuang quarry in Zhucheng, China.

Although the fossil material is limited, Zhuchengtyrannus appears to have been a large tyrannosaur, possibly approaching the size of Tarbosaurus. More complete fossils from the region may eventually clarify how this animal fit into Asian tyrannosaur evolution.

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Origins of Tyrannosaurs

The giant tyrannosaurids of the Late Cretaceous were the end result of a long evolutionary history. Early tyrannosauroids were much smaller than T. rex and lived long before the final Cretaceous ecosystems of Laramidia and Asia. For much of their early history, they were not the dominant predators.

Earlier in the Mesozoic, other large theropods such as allosauroids and carcharodontosaurids often occupied top-predator roles. As these groups declined or disappeared in some regions, tyrannosaurs expanded into the apex predator niche. Over time, some lineages evolved larger bodies, stronger skulls, forward-facing eyes, bone-crushing teeth, and reduced arms.

By the Late Cretaceous, tyrannosaurs had become the dominant large predators in Asia and Laramidia. The final giant forms, including Tarbosaurus and Tyrannosaurus rex, represent one of the most specialized predator lineages in dinosaur history.

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Recommended T. rex Dinosaur Books and Educational Items:

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References / Works Cited

Carr, T.D. & Williamson, T.E. (2010). Bistahieversor sealeyi, gen. et sp. nov., a new tyrannosauroid from New Mexico and the origin of deep snouts in Tyrannosauroidea. Journal of Vertebrate Paleontology, 30(1): 1-16. doi:10.1080/02724630903413032.

Hone, D. W. E., Wang, K., Sullivan, C., Zhao, X., Chen, S., Li, D., Ji, S., Ji, Q. & Xu, X. (2011). A new, large tyrannosaurine theropod from the Upper Cretaceous of China. Cretaceous Research, 32(4): 495-503. doi:10.1016/j.cretres.2011.03.005.

Farlow, J. O. & Brett-Surman, M. K., editors. (1997). The Complete Dinosaur. Indiana University Press.

Fiorillo, A. R. & Tykoski, R. S. (2014). A diminutive new tyrannosaur from the top of the world. PLoS ONE, 9(3): e91287. doi:10.1371/journal.pone.0091287.

Tsuihiji, T., Watabe, M., Tsogtbaatar, K., Tsubamoto, T., Barsbold, R., Suzuki, S., Lee, A. H., Ridgely, R. C., Kawahara, Y. & Witmer, L. M. (2011). Cranial osteology of a juvenile specimen of Tarbosaurus bataar from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia. Journal of Vertebrate Paleontology, 31(3): 497-517. PDF here.

Xu, X., Norell, M. A., Kuang, X., Wang, X., Zhao, Q. & Jia, C. (2004). Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids. Nature, 431: 680-684.

Xu, X., Wang, K., Zhang, K., Ma, Q., Xing, L., Sullivan, C., Hu, D., Cheng, S. et al. (2012). A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature, 484: 92-95. PDF here.

Zanno, L. E. & Napoli, J. G. (2025). Nanotyrannus and Tyrannosaurus coexisted at the close of the Cretaceous. Nature.

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