Carnosauria

Carnosauria is an extinct group of carnivorous theropod dinosaurs that lived during the Jurassic and Cretaceous periods. These fascinating creatures were part of a larger group known as theropods, which includes many famous dinosaurs like Tyrannosaurus rex. Carnosaurs are special because they had large eye sockets, long narrow skulls, and strong legs with a longer thigh (femur) than shin (tibia).

Carnosaurs first appeared around 174 million years ago during the Middle Jurassic period. The last known group of carnosaurs, called Carcharodontosauridae, went extinct about 90 million years ago in the Late Cretaceous period. Some dinosaur remains found in South America were once thought to belong to carnosaurs from even later times, but they are now believed to be from other types of theropods, such as abelisaurids and maniraptorans.

Scientists have studied these dinosaurs for many years, and their understanding of Carnosauria has changed. While some researchers once thought Carnosauria was the same as Allosauroidea, newer studies suggest it might include both Allosauroidea and Megalosauroidea. This means Carnosauria could represent most of the larger theropod dinosaurs that are not coelurosaurian. However, not all scientists agree on how these groups are related.

History of study

Carnosauria was once used to describe any large meat-eating dinosaurs, even including some that weren’t even dinosaurs, like the rauisuchian Teratosaurus. But studies in the 1980s and 1990s showed that these dinosaurs didn’t all share many features other than being big, meaning the group wasn’t scientifically accurate.

Today, scientists use careful comparison to define Carnosauria as those special dinosaurs that share a closer relation to Allosaurus than to birds. This includes groups like megalosaurids, spinosaurids, and ceratosaurs, which are now known as earlier types of theropods, while tyrannosaurids are placed in a different group called Coelurosauria.

Anatomy

Carnosaurs, a group of large meat-eating dinosaurs, had some special features. They had a triangular-shaped bone called a pubic boot and three fingers on each hand. Their legs were built strongly, with the upper leg bone being longer than the lower leg bone. They also had special bones on their tails.

These dinosaurs had strong bodies that stayed balanced, no matter how big they got. Their skeletons were designed to handle stress, especially in their hips and legs. Many had narrow skulls with sharp teeth that helped them cut through their prey. Some carnosaurs, like Allosaurus, had small scales on their skin, while others had larger, rectangular scales on their tails and feet.

Classification

Within Carnosauria, there is a more specific group called Allosauroidea. This group was first named by a scientist named Othniel Charles Marsh and later defined more clearly by other researchers. Depending on the study, Carnosauria and Allosauroidea are sometimes thought to be the same group, and in those cases, scientists often use the name Allosauroidea.

The family tree of these dinosaurs has been debated by scientists for years. Some studies suggest that certain groups like Neovenatoridae might link early carnosaurs with groups called Megaraptora. Other studies show that Megaraptora might actually be closely related to another group of dinosaurs called coelurosaurs. Recent research continues to explore these relationships, with some scientists finding that Neovenatoridae is not widely used anymore because it only includes one clear member, Neovenator.

In more recent studies, scientists have found that traditional groups like Megalosauroidea might be simpler collections of early carnosaurs rather than a distinct family. These studies also introduced new groupings, such as Carcharodontosauriformes, which includes important dinosaurs like Carcharodontosaurus and Sinraptor.

Paleobiology and behavior

Scientists have found many injuries on fossils of allosauroids, showing they often faced dangerous situations. These injuries were usually healed, suggesting allosauroids could fight off infections well, similar to modern reptiles. This healing also hints that these dinosaurs did not need to eat as often, which may have helped them avoid more injuries.

Fossils of allosauroids, such as Mapusaurus, are sometimes found together in groups. This might mean they lived in social groups, helping each other, especially when injured. However, other reasons for these groupings, like natural traps or tough living conditions, are also possible.

Paleobiogeography

The history of allosauroids, a group of large meat-eating dinosaurs, follows how the supercontinent Pangaea split into today’s continents. By the Middle Jurassic period, these dinosaurs had spread to every continent and became the first giant theropods, weighing more than two tons. They lived as top predators from the Middle Jurassic to the early Late Cretaceous periods and have been found in North America, South America, Europe, Africa, and Asia. There is also a possible discovery in Australia.

During the Early Cretaceous, carcharodontosaurids, a type of allosauroid, likely spread around the world. One theory suggests this happened through a land bridge connecting Italy’s Apulia region to Africa. Allosauroids lived on both northern and southern continents during the Jurassic and Early Cretaceous but were later replaced by tyrannosauroids in North America and Asia in the Late Cretaceous. This change was likely due to regional extinction events and the breaking of land connections between continents.