There are several dinosaur fossils claimed to be the oldest ever found, a claim many scientists have made in recent years. The oldest dinosaur bones and skulls found to date may be of a small genus of meat-eating animal measuring about 6.5 feet (2 meters) in length, but some scientists believe it was another type of reptile called a thecodont. The fossils were discovered in Brazil and are thought to be 235 to 240 million years old.

Previously, an Eoraptor, a 228 million-year-old meat-eating dinosaur, was found in Argentina. More recently, paleontologists also discovered the fossilized bones of three prosauropods, plant-eating dinosaurs that lived approximately 220 million years ago in Santa Maria, an area of southern Brazil. And finally, another claim to the oldest-known “dinosaurs” (or precursors) were prosauropods from Madagascar thought to be 230 million years old. The Eoraptor was dated using radio-isotope analysis, whereas index fossils—or the use of surrounding fossils to date a “dinosaur”—were used to date the fossil in Madagascar.