Answer:
Started 251.902 million years ago, ended 201.36 million years ago. It lasted 50.6 million years.
Step-by-step explanation:
The Triassic Period was the first period of the Mesozoic Era, which spanned 50.6 million years from 251.902 million years ago to 201.36 million years ago. It began after a major extinction event that wiped out most of the life on Earth, and marked the emergence of new vertebrates, especially reptiles. The period of time before the Triassic was called the Permian5.