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theropods - carnivorous dinosaurs

Carnivorous dinosaurs

The size of the carnivorous dinosaurs varied dramatically, from two that did not exceed the size of a chicken to the largest predators ever on Earth. Carnivorous dinosaurs are all part of the same group: theropods. Some of the early primitive dinosaurs are thought to be theropods. It is now established that birds are their descendants and that they can be considered as living theropods; one can say that their history spans more than 230 million years. Fossils of theropods are generally rarer and more diverse than those of their herbivorous counterparts. Nearly 40% of the dinosaur genera recognized by paleontologists are theropods, but most are represented by a single specimen. Their classification is therefore subject to change as new materials are discovered.

Physical characteristics

Theropods usually had a small corpulence and a big head as well as blade-shaped teeth with the edge often notched. Their long slender legs gave them greater velocity than the majority of animals. All were bipedal. They were usually provided with long curved claws ending in a point, especially in the hands. Their bones were hollow, a feature that would help their descendants, the birds, to take flight. They too had pockets of air in the skull and between the vertebrae. They had at least 5 vertebrae connected to the pelvis, and a complementary joint in the mandible that allowed lateral movement of the jaws to take large pieces of food.

Ceratosaurs

Ceratosaurus

Theropods can be divided into two main groups: ceratosaurs and tetanurans. The former originate almost exclusively from Upper Triassic and Lower Jurassic rocks, although some African and South American theropods of the Upper Cretaceous also fall into this group. Among the best known ceratosaurs are Dilophosaurus and Coelophysis, with 4 functional fingers on each hand and clawed toes.

Tetanurans

Tetanurans

Tetanurans include all other theropods. They had three functional fingers at most on each hand, and three large toes and a smaller one on the inside. Among them were the generally large carnosaurs, including Allosaurus and Sinraptor. This group has undergone significant changes in recent years due to a new classification of many fossils found. Initially, carnosaurs were grouped only by their large size, but Tyrannosaurus, the largest of all, is no longer considered a member of the group. The coelurosaurs, most of which were Cretaceous tetanurians, included giants such as the imposing Tyrannosaurus, and strange creatures such as dromaeosaurids, ostrich-like ornithomimosaurs, and crested Oviraptors. Ornithomimosaurs and Oviraptor being virtually toothless, one may wonder what they ate and how they processed their food.

Dromaeosaurs and theropods related to birds

Dromaeosaur

Dromaeosaurs had a skeleton reminiscent of birds and a retractable claw on the second finger that could fatally injure prey. Recent discoveries, including those made in China, have revealed the existence of a large number of theropods related to birds, demonstrating the link between the two groups. Several specimens, including Sinosauropteryx and Caudipteryx, were found with feathers or similar structures. It is therefore possible that this type of structure has been more widespread among theropods, but because of the vagaries of fossilization, it has not been preserved on the remains discovered until then.

Various habits

As a majority group of the time, theropods had very diverse habits such as carnivores today. The discovery of dozens of Coelophysis at Ghost Ranch in New Mexico and the Cleveland-Lloyd Quarry Allosaurus in Utah shows that at least some theropods lived in groups. But the fossils of theropods discovered to date being mostly isolated specimens, it is supposed that they were rather solitary animals.