Nyasaurus is believed to be the first ever dinosaur.

The first dinosaurs evolved during the Late Triassic period, approximately 230 million years ago. The exact identity of the first dinosaur is difficult to determine, as the distinction between dinosaurs and their close reptilian relatives is a gradual process. However, one of the earliest known dinosaurs is believed to be Nyasasaurus, which lived around 243 million years ago.

Nyasasaurus is considered one of the earliest dinosaurs because its fossil remains display several dinosaur-like characteristics, including a more upright stance, longer hind limbs, and certain features of the hip structure that are unique to dinosaurs. Its fossils were discovered in Tanzania, Africa, and provide valuable insights into the early evolutionary stages of dinosaurs.

Although Nyasasaurus is a strong candidate for one of the first dinosaurs, it's important to note that the classification and understanding of early dinosaur evolution is an ongoing field of research. New discoveries and analyses continually refine our knowledge and shed light on the early origins and diversification of dinosaurs.

Ultimately, the first dinosaur alive would have been an individual belonging to a species that lived during the Late Triassic period. Over time, dinosaurs became one of the dominant groups of animals on Earth and evolved into a wide array of species, showcasing an extraordinary diversity that lasted for millions of years until their extinction approximately 66 million years ago.