page_title: Tyrannosauridae
section_title: Distribution
hierarchical_section_title: Tyrannosauridae / Paleoecology / Distribution
caption_attribution_description: English: Map of tyrannosauroid fossil localities as of December 2007. I used the blank political map of the world commonly used on Wikipedia ((BlankMap-World.png). Keep in mind that the land masses would not have been in the same places they are today in the Jurassic and Cretaceous periods.
context_page_description: Tyrannosauridae is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three. All of these animals lived near the end of the Cretaceous Period and their fossils have been found only in North America and Asia.
  Although descended from smaller ancestors, tyrannosaurids were almost always the largest predators in their respective ecosystems, putting them at the apex of the food chain. The largest species was Tyrannosaurus rex, one of the largest and most massive known land predators, which measured over 12.3 metres in length and according to most modern estimates 8.4 metric tons to 14 metric tons in weight. Tyrannosaurids were bipedal carnivores with massive skulls filled with large teeth. Despite their large size, their legs were long and proportioned for fast movement. In contrast, their arms were very small, bearing only two functional digits.
  Unlike most other groups of dinosaurs, very complete remains have been discovered for most known tyrannosaurids.
context_section_description: While earlier tyrannosauroids are found on all three northern continents, tyrannosaurid fossils are known only from North America and Asia. Sometimes fragmentary remains uncovered in the Southern Hemisphere have been reported as "Southern Hemisphere tyrannosaurids," although these seem to have been misidentified abelisaurid fossils. The exact time and place of origin of the family remain unknown due to the poor fossil record in the middle part of the Cretaceous on both continents, although the earliest confirmed tyrannosaurids lived in the early Campanian stage in western North America.
  Tyrannosaurid remains have never been recovered from eastern North America, while more basal tyrannosauroids, like Dryptosaurus and Appalachiosaurus, persisted there until the end of the Cretaceous, indicating that tyrannosaurids must have evolved in or dispersed into western North America after the continent was divided in half by the Western Interior Seaway in the middle of the Cretaceous. Tyrannosaurid fossils have been found in Alaska, which may have provided a route for dispersal between North America and Asia. Alioramus and Tarbosaurus are found to be related in one cladistic analysis, forming a unique Asian branch of the family. This was later disproven with the discovery of Qianzhousaurus and the description of the tyrannosaur family Alioramini. Tyrannosaurid teeth from a large species of unknown variety were discovered in the Nagasaki Peninsula by researchers from the Fukui Prefectural Dinosaur Museum, further expanding the range of the group. The teeth were estimated to be 81 million years old (Campanian Age).
  Of the two subfamilies, tyrannosaurines appear to have been more widespread. Albertosaurines are unknown in Asia, which was home to the tyrannosaurines, such as Tarbosaurus and Zhuchengtyrannus, and Qianzhousaurus and Alioramus of the Alioramini. Both the Tyrannosaurinae and Albertosaurinae subfamilies were present in the Campanian and early Maastrichtian stages of North America, with tyrannosaurines like Daspletosaurus ranging throughout the Western Interior, while the albertosaurines Albertosaurus and Gorgosaurus are currently known only from the northwestern part of the continent.
  By the late Maastrichtian, albertosaurines appear to have gone extinct, while the tyrannosaurine Tyrannosaurus roamed from Saskatchewan to Texas. This pattern is mirrored in other North American dinosaur taxa. During the Campanian and early Maastrichtian, lambeosaurine hadrosaurs and centrosaurine ceratopsians are common in the northwest, while hadrosaurines and chasmosaurines were more common to the south. By the end of the Cretaceous, centrosaurines are unknown and lambeosaurines are rare, while hadrosaurines and chasmosaurines were common throughout the Western Interior. A study published in the journal Scientific Reports on February 2, 2016 by Steve Brusatte, Thomas Carr et al. indicates that during the later Maastrichtian, Tyrannosaurus itself might have been partially responsible for the extinction of the other tyrannosaurids in most of western North America. The study indicates that Tyrannosaurus might have been an immigrant from Asia as opposed to having evolved in North America (possibly a descendant of the closely related Tarbosaurus) that supplanted and outcompeted other tyrannosaurids. This theory is further supported by the fact that few to no other types of tyrannosaurid are found within Tyrannosaurus' known range.
caption: While earlier tyrannosauroids are found on all three northern continents, with possible remains from Australia, tyrannosaurid fossils (blue dots) are known only from North America and Asia
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