Ceratosauria

Ceratosauria is a group of dinosaurs called ceratosaurs. They are part of the theropod group and share a common ancestor with Ceratosaurus that is more recent than their connection to birds. The oldest known ceratosaur, Saltriovenator, lived about 199 million years ago during the Jurassic period.

Ceratosaurs include three main families: Ceratosauridae, Noasauridae, and Abelisauridae. These dinosaurs are mostly found in the Southern Hemisphere. Early scientists thought other dinosaurs like coelophysoids and dilophosaurids were also ceratosaurs, but recent studies show they are not closely related.

The name Ceratosauria comes from Ceratosaurus nasicornis, the first ceratosaur discovered. It was described in 1884 by O.C. Marsh. Ceratosaurs were usually medium-sized predators, though some, like Carnotaurus, were larger, and others, like noasaurs, were much smaller. Key features of ceratosaurs include a strong skull with extra decorations and shorter arms. These traits became more noticeable in later ceratosaurs, especially the abelisaurs. Because many ceratosaur fossils are incomplete, much about their history and relationships is still unclear and widely discussed.

History of study

Ceratosauria was first described by O.C. Marsh in the American Journal of Science in 1884. He was talking about the newly found dinosaur called C. nasicornis. He noticed that this dinosaur had a special feature in its feet, just like another dinosaur called Archaeopteryx. Because of this, Marsh thought Ceratosauria was very close to Archaeopteryx and its group. He also gave the name Ceratosauridae to this group in 1884.

Later, another scientist, Edward Drinker Cope, disagreed and said Ceratosauria wasn’t a real group. But in 1920, another scientist named Gilmore supported the idea again. Still, for many years, scientists argued about whether Ceratosauria was real or not.

In 1986, Jacques Gauthier helped clear things up. He put most meat-eating dinosaurs into two big groups: Ceratosauria and Tetanurae. He included ceratosaurs and coelophysoids in Ceratosauria. By the early 1990s, Abelisauridae was also added to Ceratosauria. This way of grouping stayed until around 2000. After that, many scientists decided that coelophysoids didn’t belong in Ceratosauria anymore. This is the view most scientists hold today.

Phylogeny

Most scientists think that Ceratosauria separated from other meat-eating dinosaurs in the Late Triassic or earliest Jurassic period. However, the oldest known ceratosaur, Saltriovenator zanellai, lived in the Early Jurassic, about 199 million years ago. Finding fossils from this time is hard, and some scientists believe this is because fossils from this period are rare, not because ceratosaurs didn’t exist.

Ceratosauria includes three main groups: Ceratosauridae, Noasauridae, and Abelisauridae. Abelisauroidea, a larger group, includes Abelisauridae and Noasauridae. Noasaurids had longer arms than abelisaurids, which had very small arms. Noasaurids were good runners and came in different sizes, from small to quite large. Abelisauroids were common in the Southern Hemisphere during the Cretaceous period but had a wider distribution earlier on.

Paleobiology

Anatomy

Ceratosaurs had some special features. Their skulls were often taller and more decorated, and their front legs were shorter than other similar dinosaurs. They also had bones in their hips and ankles that were fused together.

One well-known ceratosaur, Ceratosaurus, had a skull shape that was closer to older theropods, with a special crest on its nose. It had big teeth, which might have made it hard to hunt very large animals. Another group, the abelisaurids, took these features even further. For example, Carnotaurus had very short front legs. Scientists think these dinosaurs might have been better at eating dead animals than hunting live ones. Even with their short legs, ceratosaurs always kept all their fingers and important limb bones.

Ceratosaurus had two kinds of teeth: some with ridges and others with patterns in the outer layer. Both types had a teardrop shape and a sharp edge down the middle.

We know the most about the skeletons of advanced abelisaurids like Carnotaurus and Aucasaurus. Many features we see in their skulls are also found in another group called carcharodontosaurids. Some scientists think these two groups might have been related. Another group, the noasaurids, had a special curved claw on one of their toes, similar to some other small theropods.

Paleoecology

Geography

Ceratosaurs seem to have lived all over the world, but mostly disappeared from northern areas like Laurasia by the time of the Cretaceous period. Some scientists think a few might have come back from southern areas like Gondwana. We still haven’t found any proof of ceratosaurs living in North America during the Cretaceous.

Abelisaurids did very well in Gondwana, especially during the Cretaceous. Recently, some older fossils have been found that show they might have lived even earlier than we thought. Some scientists think a big desert might have kept abelisaurids in the southern parts of Gondwana for a long time. We often find fewer ceratosaurs from the late Cretaceous in places where other types of dinosaurs, like tetanurans in Africa or coelurosaurs in North America and Asia, were common.

Diet

Like most meat-eating dinosaurs, ceratosaurs ate other animals. But some, like noasaurs such as Limusaurus and Berthasaura, may have eaten plants or both plants and animals because they didn’t have teeth. Some scientists think Ceratosaurus might have eaten a lot of fish, but others disagree. We know Ceratosaurus sometimes ate big animals because we’ve found its tooth marks on them, meaning it might have been a scavenger.

The abelisaurids had interesting jaws, and scientists aren’t sure exactly what they ate. Some think Carnotaurus had a weak bite good for catching small animals, while others think it could hurt big animals. Some even think its jaws were made for scavenging. Scientists are still studying abelisaurids a lot, especially since we’re finding more of them. Studies on Majungasaurus show it grew slowly, taking about 20 years to become an adult — and this might have been normal for all abelisaurids.

Noasaurines lived in the late Cretaceous and are only found in southern places like South America, Madagascar, and India. Elaphrosaurines were lighter-built dinosaurs with long necks and legs and small skulls. If Limusaurus is an example, adult elaphrosaurines didn’t have teeth and probably had beaks. Because we’ve found special stones called gastroliths in them and their chemistry looks like that of plant-eating dinosaurs, they likely ate plants as adults.

Paleoenvironment

Ceratosaurs like those in the Ceratosauridae family lived alongside other big predators. In North America, they probably competed with allosaurids for food such as sauropods. In Africa and Europe, they also shared their homes with other large predators.

Most abelisauroid ceratosaurs have been found in Madagascar, Asia, or Africa. The Abelisauridae family thrived during the Cretaceous on the southern supercontinent of Gondwana, and today we find their fossils in Africa, South America, the Indian subcontinent, and Madagascar. In Madagascar, Majungasaurus was discovered by a French scientist and was one of the most common abelisauroids. In South America, we’ve found many abelisauroids like Skorpiovenator, Quilmesaurus, Aucasarus, Ilokelesia, and Pyconemosaurus. Kurupi itaata is an important discovery because it’s one of the few theropod fossils from the Bauru Basin in South America, and it helps us learn more about these dinosaurs in that area.