Neotetanurae

Neotetanurae is a clade of theropod dinosaurs that encompasses most of the familiar large predatory dinosaurs like Tyrannosaurus, Allosaurus, and Spinosaurus. The name Neotetanurae means "new shaking tails" and refers to a significant evolutionary development in the tail structure of these dinosaurs. Specifically, they possess a stiffened tail due to elongated, interlocking vertebral processes, which provided greater balance and maneuverability during locomotion and hunting. This anatomical feature distinguishes them from earlier theropods.

This group is characterized by several other shared derived traits, including a specialized wrist joint that allowed for greater flexibility and an increasingly reduced number of digits, typically with only three functional fingers. The phylogenetic placement of Neotetanurae within Theropoda is well-established, with its origin tracing back to the Middle Jurassic period. It is broadly divided into two major subgroups: Spinosauridae, which includes giant piscivorous dinosaurs like Spinosaurus, and Allosauroidea, which comprises well-known predators such as Allosaurus and Carcharodontosaurus. The Tyrannosauroidea, which includes Tyrannosaurus rex, is now widely considered to be within the Allosauroidea or a closely related sister group. Understanding Neotetanurae is crucial for reconstructing the evolutionary history and ecological dynamics of predatory dinosaurs during the Mesozoic Era.