Triassic

The Triassic is a geological period and the first of the three periods that make up the Mesozoic era. It lies between the earlier Permian period and the later Jurassic period. The name comes from three rock formations from central Europe that were distinguished by scientists in the nineteenth century.

The beginning of the Triassic was preceded by the mass extinction at the end of the Permian, which is believed to have affected a large percentage of marine and terrestrial species. Consequently, Triassic fossil records show an ecosystem recovering, with new groups of animals filling the empty ecological niches.

Divisions of the period

The period is divided into three major subdivisions: Early Triassic, Middle Triassic, and Late Triassic. Each subdivision has lower divisions identified by fossil types, particularly ammonoids and conodonts, which are used to date rock sequences.

Geography and climate

During much of the period, the major landmasses were united into a single supercontinent called Pangaea, surrounded by a vast ocean. The interior of the continent was extremely arid, because rainfall could not reach the inland regions. Consequently, many Triassic rock formations are red sediments derived from deserts, containing salt and gypsum. By the end of the period, Pangaea had begun to break apart.

Life

The Triassic saw the emergence of the earliest dinosaurs, which began as small bipedal animals. There also appeared early mammaliaforms and flying pterosaurs. The oceans were inhabited by large marine reptiles such as ichthyosaurs. Plant life was dominated by conifers, cycads, and ferns.