What is Tyrannosauridae?

The least inclusive clade containing Tyrannosaurus rex, Gorgosaurus libratus and Albertosaurus sarcophagus. Originally named "Deinodontidae" by Edward Drinker Cope in 1866, Tyrannosauridae is a group of large-bodied, multi-ton coelurosaurian theropods with massive skulls, forward-pointing eyes for binocular vision, powerful legs with what boffins call an "arctometatarsus", and pathetically small but powerful arms with only two functional fingers.

Tyrannosauridae contains two sub-families; Albertosaurinae (the slender tyrannosaurids, including Albertosaurus and Gorgosaurus) and Tyrannosaurinae (the robust tyrannosaurids, including Tarbosaurus and Tyrannosaurus ), and while all were very large by modern predator standards some were "only" nine meters in length and one (Nanuqsaurus) was a mere five and a half.

Unlike the smaller, cosmopolitan Tyrannosauroidea — the group which they fall inside of — tyrannosaurids are found exclusively in Late Cretaceous formations of Asia and North America where they were always the top predators in their ecosystem.

Until recently, it was thought that their relatively short, rounded and robust snouts with massive bone-crushing teeth and an expanded rear of the skull which allowed for huge muscle attachment and fully forward-pointing eyes appeared around 70 million years ago. But the discovery of Lythronax argestes in Utah's Mid-Campagnian-aged Wahweap Formation pushed the origin of tyrannosaurid-skull-robustness back some 10 million years.

Click here to view Dinochecker's A-Z list of tyrannosaurids. Tyrannosauridae is derived from the Greek "tyrannos" (tyrant) + Greek "sauros" (lizard) + Latin "-idae" (family).