This 5 September 2018 video says about itself:
In this video we shall take a look into the earliest and first dinosaurs to have ever existed in this world.
These early dinosaurs are the oldest to be discovered in fossils of the Triassic age timeline.
The earliest dinosaurs are small in size and are mainly bipedal. … The comparison of the first dinosaurs and the large dinosaurs is really contrasting since the larger dinosaurs dwarf the early dinosaurs in height and weight.
The Saturnalia predates the Eoraptor by 1 million years and the Nyasasaurus predates the others by more than 10 million years.
The Nyasasaurus is the earliest dinosaur we know, but definitely not the first since there is a probability that other dinosaurs might be found in the future. So, enjoy this video on the First / earliest dinosaurs comparison and timeline. The timeline is in the millions of years in the Triassic.
Timeline: Riojasaurus – 227 MYA, Alwalkeria/Herrerasaurus/Pisanosaurus/Saurikosaurus/Chromogisaurus – 230 MYA, Eoraptor – 231 MYA, Saturnalia – 232 MYA, Spondylosoma – 242 MYA and Nyasasaurus – 243 MYA.