Tyrannosauridae

Tyrannosauridae was a group of large coelurosaurian theropods that lived during the final stages of the Cretaceous. They are known for a striking head-to-arm ratio: massive skulls, sometimes reaching 1.5 m, paired with arms roughly a metre long that ended in only two functional fingers. Their skulls were reinforced and air-filled, with nasal bones fused to withstand high impact. They possessed thick, oval-shaped teeth often compared to bananas. These were capable of puncturing and crushing bone, evidence of which has been found in the marked vertebrae and pelvises of their prey.

The family is divided into two subfamilies. Albertosaurinae, including Albertosaurus and Gorgosaurus, were leaner and faster animals. Tyrannosaurinae, which includes Tyrannosaurus, Tarbosaurus, Daspletosaurus, and Zhuchengtyrannus, had heavier builds, more robust skulls, and more powerful bites. This division likely allowed different tyrannosaurid species to share the same ecosystem by occupying different ecological niches.

As coelurosaurs, tyrannosaurids belong to a lineage where feathers were the ancestral condition. However, researchers debate whether adult tyrannosaurids remained feathered. While the basal tyrannosauroid Yutyrannus had long filamentous feathers, skin impressions from Tyrannosaurus and its closer relatives show pebbly scales across much of the body. Current consensus suggests that large adults were primarily scaly, perhaps retaining only sparse patches of feathers.

Studies of bone histology indicate that tyrannosaurids underwent a rapid growth spurt during adolescence. For instance, a teenage T. rex gained approximately 2 kg per day. Adult T. rex had an estimated bite force of 35,000–60,000 N, the highest of any known land vertebrate. Their diet consisted of large herbivores like Triceratops and Edmontosaurus, as confirmed by stomach contents and tooth marks on fossils. Healed wounds found on tyrannosaurid skulls suggest they engaged in face-biting, an aggressive behaviour possibly linked to mating or social hierarchy. While trackways and fossil clusters like the "Wyrex" assemblage hint at social groups, it is still unclear whether they hunted in coordinated packs.

• Sue (FMNH PR 2081, T. rex) — Field Museum.
• Stan (BHI 3033, T. rex) — sold at auction 2020, currently being scientifically described before display in Abu Dhabi.
• Scotty (RSM P2523.8, T. rex) — possibly the largest known T. rex by mass, Royal Saskatchewan Museum.
• Bloody Mary / Tristan (Tarbosaurus / T. rex specimens) — multiple notable European museum mounts.

The Nanotyrannus question is the most persistent: is Nanotyrannus lancensis a valid small tyrannosaurid genus, or are all "Nanotyrannus" specimens juvenile T. rex? Recent work (Longrich & Saitta 2024) reignited the case for genus validity, but the majority view through the 2010s and into the 2020s leans toward juvenile T. rex, citing growth-series studies. Other debates: how feathered adult tyrannosaurids were, whether T. rex was an obligate predator or an opportunistic scavenger (consensus is opportunistic apex predator), and the exact phylogenetic position of basal tyrannosauroids like Yutyrannus.

Tyrannosaurids are the cultural face of dinosaurs. Jurassic Park's T. rex (1993) shaped a generation's mental image; Walking with Dinosaurs (1999) brought a tracking-cam perspective; Prehistoric Planet (2022) presented current-consensus tyrannosaurids with feathered chicks and complex social behaviour.

• tyrannosaurus
• tyrannosaurus-rex
• theropoda

• Brusatte, S. L., et al. (2010). Tyrannosaur paleobiology: new research on ancient exemplar organisms. Science, 329, 1481–1485.
• Carr, T. D. (2020). A high-resolution growth series of Tyrannosaurus rex. PeerJ, 8, e9192.
• Xu, X., et al. (2012). A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature, 484, 92–95.
• Persons, W. S., Currie, P. J., & Erickson, G. M. (2020). An older and exceptionally large adult specimen of Tyrannosaurus rex. Anatomical Record, 303, 656–672.