Nyasasaurus parringtoni
If Nyasasaurus parringtoni isn't the earliest dinosaur, it's the closest thing to it that scientists have found so far. Working from an upper arm bone and six vertebrae found in Tanzania in the 1930s, researchers surmise that Nyasasaurus would have been about the size of a Labrador retriever, but with a much longer tail. In a paper published last year in Biology Letters.
They argue that it lived in the southern part of the supercontinent Pangea about 243 million years ago, predating all other known dinosaurs by at least 10 million years. Image: Natural History Museum, London/Mark Witton