Carnosauria

Lore & Background

Carnosauria has traditionally been used as a dumping ground for all large theropods, including non-dinosaurs such as the rauisuchian Teratosaurus. However, analyses in the 1980s and 1990s revealed that the group shared very few characteristics, making it polyphyletic. Most former carnosaurs were reclassified as more primitive theropods or placed in Coelurosauria. Modern cladistic analysis defines Carnosauria as those tetanurans sharing a more recent common ancestor with Allosaurus than with modern birds. Distinctive characteristics of carnosaurs include large eye sockets, a long narrow skull, and modifications of the legs and pelvis such as the femur being longer than the tibia. They also have a triangular-shaped pubic boot, three fingers per hand with the second and third digits approximately equal in length, and chevron bases on their tails with anterior and posterior bone growth. The largest carnosaurs can reach up to 10 meters in length. Their skulls are about 2.5 to 3 times longer than tall, with serrated teeth that are flat and have equally-sized denticles on both edges. Skin impressions from Allosaurus and Concavenator show small scales, broad scutate scales, and rectangular scutate scales. Concavenator preserves a series of knobs on the ulna that have been interpreted by some authors as quill knobs, though this interpretation has been questioned. The last definitive carnosaur family, Carcharodontosauridae, became extinct in the Turonian epoch of the Late Cretaceous around 90 million years ago. Some theropod remains from the Maastrichtian epoch in South America were once suggested to be carcharodontosaurids but were later reinterpreted as other theropod groups.

Reader's Guide

Carnosauria holds a significant place in the study of dinosaur evolution as a major group of large carnivorous theropods that dominated many Jurassic and Cretaceous ecosystems. The group's history of classification illustrates the shift from a polyphyletic 'wastebasket' taxon to a more rigorously defined clade based on shared derived characteristics. Modern cladistic analysis has refined Carnosauria to include tetanurans more closely related to Allosaurus than to birds, though its exact composition remains debated, with some studies including both Allosauroidea and Megalosauroidea. The anatomical features of carnosaurs—such as their long narrow skulls, serrated teeth, and limb proportions—suggest they were specialized predators capable of slicing flesh. Their large size, with some reaching 10 meters in length, places them among the largest terrestrial carnivores of their time. The discovery of skin impressions provides rare direct evidence of their integument, showing scales of varying sizes. The extinction of the last definitive carnosaur family, Carcharodontosauridae, around 90 million years ago, marks the end of a lineage that had persisted for over 80 million years. However, the group's legacy continues through ongoing phylogenetic debates, particularly regarding the affinities of megaraptorans and other enigmatic theropods. Carnosauria remains a key subject for understanding theropod diversity, biogeography, and the evolutionary trends toward gigantism in predatory dinosaurs.

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 a femur longer than the tibia and a triangular-shaped pubic boot.
• Skin impressions from Allosaurus show small scales measuring 1 to 3 millimeters on the side of the torso and mandible.