Triassic

American  

[trahy-as-ik] / traɪˈæs ɪk /

adjective

1. noting or pertaining to a period of the Mesozoic Era, occurring from 230 to 190 million years ago and characterized by the advent of dinosaurs and coniferous forests.

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noun

1. Also Trias the Triassic Period or System.

Triassic British  

/ traɪˈæsɪk /

adjective

1. of, denoting, or formed in the first period of the Mesozoic era that lasted for 42 million years and during which reptiles flourished

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noun

1. the Triassic period or rock system

Triassic Scientific  

/ trī-ăs′ĭk /

1. The earliest period of the Mesozoic Era, from about 245 to 208 million years ago. During the early part of the Triassic Period the supercontinent Pangaea was located along the equator; by the end of the Triassic it had started to split up. Land life diversified in the Triassic in response to the mass extinctions of the end of the Paleozoic. Conifers, cycads, marine reptiles, dinosaurs, and the earliest mammals first appeared.

2. See Chart at geologic time

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Other Word Forms

• post-Triassic adjective

Etymology

Origin of Triassic

1835–45; Trias the three-part series of strata characterizing the period (< German < Greek triás; see triad) + -ic

Example Sentences

As the Triassic period ended, dinosaurs quickly became the dominant land animals.

From Science Daily • Apr. 15, 2026

Thrinaxodon belonged to a group called cynodonts, animals from the early Triassic period that show a mix of reptile and mammal traits.

From Science Daily • Jan. 19, 2026

"These sharks became extinct during the Triassic period when around 96 per cent of creatures died out – that was far more than during the Cretaceous period which marked the end of the dinosaurs. "

From BBC • Dec. 27, 2025

The species lived at the end of the Triassic period, during which the first dinosaurs and the ancestors of mammals started to appear, the researchers said.

From Barron's • Oct. 16, 2025

Most of these are also reasonably well known: Cretaceous, Jurassic, Triassic, Silurian, and so on.*

From "A Short History of Nearly Everything" by Bill Bryson