Dinosaurs are a diverse group of animals that appeared 243 million years ago and became the dominant terrestrial animals 200 million years ago. Unfortunately, most were wiped out possibly by a meteor strike 65 million ago. Dinosaurs are classified as avian and non-avian; avian dinosaurs are ancestors of modern-day birds. Researchers of the early 20th century believed that dinosaurs were cold-blooded and sluggish, but advanced research in the 1970s indicates that they were active with elevated metabolisms and social interactions. They were either carnivores or herbivores. It is interesting to note that both avian and non-avian dinosaurs built nests and laid eggs. In 2018, researchers discovered that some species of dinosaurs were covered by feathers and fur dismissing the previous theory that all dinosaurs were covered by either scales or bare skin. Modern taxonomy classifies all dinosaurs as reptiles.
Reptiles, Mammals Or Birds?
Dinosaurs portray the characteristics of birds, mammals, and reptiles. Avian dinosaurs were the ancestors of modern-day birds creating an illusion that they should be categorized as birds. They were also gigantic, bipedal or quadrupedal, and consumed large quantities of food creating an illusion of mammals. Recent research has revealed that they were warm-blooded animals. However, research has also discovered that warm-blooded reptiles such as the tegu also exist. Modern taxonomy classifies all dinosaurs as reptiles and not birds or mammals because most of the characteristics of dinosaurs are found in reptiles than in the latter species. Most of the giant dinosaurs went extinct after the meteor strike, but smaller ones such as the Xixianykus evolved into birds.
Dinosaurs existed at a time when animals exhibited similar characteristics. Some of the animals we see today evolved from entirely different animals 65 million years ago. General classification categories fish as the first vertebrates to appear on the planet. Some species of fish later evolved into amphibians, and some amphibians evolved into reptiles. The similarity in physical appearance of animals may create an illusion that they are firmly related than they are. Crocodiles evolve slower than any other reptiles, and it sounds inconceivable that they are closely related to birds than to lizards despite their physical resemblance and different classification. Birds are living descendants of dinosaurs, but they acquired their characteristics by evolution rather than genetic lineage.
Dinosaurs Were Reptiles
If dinosaurs existed today, they would be categorized as reptiles under the subspecies Archosaurs that also include crocodiles. Unlike crocodiles and lizards whose legs extend from either side of the body, the legs of dinosaurs extend from beneath. The pelvic structures resembled those of lizards and crocodiles and moved in an almost similar manner. They built nests and laid eggs; a characteristic of both birds and reptiles.