Was the Cretaceous period the shortest?

No, the Cretaceous period was not the shortest; in fact, it was one of the longest periods in the Mesozoic Era, lasting about 79 million years, from approximately 145 million to 66 million years ago. In comparison, the Triassic period was shorter, lasting about 50 million years, while the Jurassic period lasted about 56 million years. The Cretaceous is notable for its diverse dinosaurs and the eventual mass extinction event that marked its end.