The Mesozoic Era lasted approximately 185.5 million years; it began around 251 million years ago with the Triassic Period, and it remained until 65.5 million years ago with the end of the Cretaceous Period. The Mesozoic Era contained three distinct time periods: the Jurassic Period followed the Triassic Period, spanning a time frame of 199.6 to 145.5 million years ago, while the Cretaceous Period ended the Mesozoic Era.
The term mesozoic means "middle animals." New animals and vegetation arrived during the course of the Mesozoic Era. Several species of dinosaurs emerged during the Triassic Period, but dinosaur diversity occurred later in the Jurassic Period. However, dinosaurs enjoyed only a brief growth in population. With the exception of several bird species, dinosaurs' numbers dwindled; many species failed to exist following the Cretaceous Period.
According to researchers at the University of California Museum of Paleontology, the last dinosaur remains from the Mesozoic Era appeared in modern-day Montana. While dinosaurs fared poorly during the Mesozoic Period, vegetation blossomed. Plants and flowers appeared in larger numbers on land and in water. Common plants, including ferns and cycads emerged during that time, along with early ancestors of modern conifers and angiosperms. Fossils from the Mesozoic Era exist around the world in places like the United States, Germany, Argentina and Ethiopia.