Jura-Triassic is a geological time period that spans from around 201 to 145 million years ago. Synonyms for Jura-Triassic include the Jurassic-Cretaceous boundary and the Lower Jurassic, as the Jura period is part of the Mesozoic Era's Jurassic period. The Triassic period is also part of the Mesozoic Era, precedes the Jura period and is sometimes simply called the Trias. Together, the two periods make up the early or lower half of the Jurassic period. The Jura-Triassic period is known for the emergence of many plant and animal species on land, as well as the rise of the dinosaurs.