When did the first dinosours appear on earth?
The oldest dinosaur types are known from rocks in Argentina and Brazil and are about 230 million years old. The most primitive of these types, Eoraptor, was a small meat-eating dinosaur. Because Eoraptor’s skeleton shows some advanced skeletal features, older dinosaurs may yet be found.
Are all fossil animals dinosours?
No. Dinosaurs are a group of ancient reptiles that had a set of particular skeletal features. The hips, hind legs, and ankles were specialized and allowed the legs to move directly under the body, rather than extending out from the side of the body as in modern lizards. This arrangement enabled dinosaurs to bring their knees and ankles directly below their hips and provided the necessary attachments for very strong leg muscles. Dinosaur skeletons were well designed for supporting a large body, for standing erect (upright), and for running. The front legs were adapted for grasping prey, for supporting weight, or for walking and running. The skulls of dinosaurs were designed for maximum strength, for minimum weight, and (in some cases) for grasping, holding, or tearing at prey. These skeletal features separated dinosaurs from other ancient reptiles such as Dimetrodon, the plesiosaurs, and pterosaurs. Fossil mammals, like mammoths and “saber-toothed tigers” (e.g., Smilodon), are also often incorrectly called dinosaurs.
Did people and dinosours live at the same time?
No! After the dinosaurs died out, nearly 65 million years passed before people appeared on Earth. However, small mammals (including shrew-sized primates) were alive at the time of the dinosaurs. Many scientists who study dinosaurs (vertebrate paleontologists) now think that birds are direct descendants of one line of carnivorous dinosaurs, and some consider that they in fact represent modern living dinosaurs. This theory remains under discussion and shows that there is still much we don’t know about dinosaurs.