Carnosauria

Lore & Background

Carnosauria is an extinct group of carnivorous theropod dinosaurs that lived during the Jurassic and Cretaceous periods. Historically, the group was used as a catch-all for any large theropod, even including non-dinosaurian reptiles like the rauisuchian *Teratosaurus*. However, studies in the 1980s and 1990s demonstrated that these animals shared very few unique traits, making the traditional grouping polyphyletic. Consequently, most former carnosaurs—such as megalosaurids, spinosaurids, and ceratosaurs—were reclassified as more primitive theropods, while others like tyrannosaurids were placed in Coelurosauria. Modern cladistic analysis defines Carnosauria as those tetanurans sharing a more recent common ancestor with *Allosaurus* than with modern birds. Some recent research has revived Carnosauria as a clade including both Allosauroidea and Megalosauroidea, though other researchers find these groups unrelated. Distinctive anatomical features include large eye sockets, a long narrow skull, and a femur longer than the tibia. Carnosaurs also possess a triangular-shaped pubic boot, three-fingered hands with the second and third digits of similar length, and chevron bases on the tail with both anterior and posterior bone growth. The largest carnosaurs reached up to ten meters in length. Their skulls are typically two and a half to three times longer than tall, with flat, serrated teeth bearing equally-sized denticles on both edges. Cranial vault volume ranged from about 95 milliliters in *Sinraptor* to 250 milliliters in *Giganotosaurus*. Skin impressions from *Allosaurus* and *Concavenator* show small scales, broad scutate scales on the neck and underside of the tail, and small scales on the feet. A series of knobs on the ulna of *Concavenator* have been interpreted by some as possible quill knobs, though this is debated. The last definitive carnosaur family, Carcharodontosauridae, became extinct in the Turonian epoch of the Late Cretaceous.

Reader's Guide

Carnosauria represents a significant group of large predatory dinosaurs that dominated terrestrial ecosystems during the Jurassic and Cretaceous periods. Their distinctive anatomy, including large eye sockets, long narrow skulls, and modifications of the legs and pelvis, allowed them to become effective predators. The group's classification has been highly controversial, with some studies reviving Carnosauria to include both Allosauroidea and Megalosauroidea, while others find these groups unrelated. The last definitive carnosaur family, Carcharodontosauridae, became extinct around 90 million years ago, though some later theropod remains once thought to be carcharodontosaurids were reinterpreted as belonging to other groups. Carnosaurs scaled their limbs relative to body size similarly to tyrannosaurids, and during the Cretaceous some grew to sizes comparable to the largest tyrannosaurids. Their fossils, including skin impressions from Allosaurus and Concavenator, provide insights into their integument and biology. The ongoing debate over their classification highlights the dynamic nature of paleontological research.

Did You Know?

• The last definitive carnosaur family, Carcharodontosauridae, became extinct in the Turonian epoch of the Late Cretaceous around 90 million years ago.
• Distinctive characteristics of carnosaurs include large eye sockets, a long narrow skull, and the femur being longer than the tibia.
• Carnosaur teeth are flat with equally-sized denticles on both edges, and the flat side faces the sides of the skull.