Mesozoic

American  

[mez-uh-zoh-ik, mes-, mee-zuh-, -suh-] / ˌmɛz əˈzoʊ ɪk, ˌmɛs-, ˌmi zə-, -sə- /

adjective

1. noting or pertaining to an era occurring between 230 and 65 million years ago, characterized by the appearance of flowering plants and by the appearance and extinction of dinosaurs.

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noun

1. the Mesozoic Era or group of systems.

Mesozoic British  

/ ˌmɛsəʊˈzəʊɪk /

adjective

1. of, denoting, or relating to an era of geological time that began 250 000 000 years ago with the Triassic period and lasted about 185 000 000 years until the end of the Cretaceous period

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noun

1. the Mesozoic era

Mesozoic Scientific  

/ mĕz′ə-zō′ĭk /

1. The era of geologic time from about 245 to 65 million years ago. The Mesozoic Era was characterized by a drastic change in plants and animals. In the early part of the Mesozoic, ferns, cycads, and ginkgos were dominant; later, gymnosperms and angiosperms developed. Dinosaurs also first appeared in the Mesozoic and, with the exception of birds, became extinct at the end of the era.

2. See Chart at geologic time

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Other Word Forms

• post-Mesozoic adjective

Etymology

Origin of Mesozoic

First recorded in 1830–40; meso- + zo- + -ic

Example Sentences

Scientists now believe the split between octopuses and their 10-armed relatives happened in the Mesozoic era, not hundreds of millions of years earlier as previously thought.

From BBC • Apr. 8, 2026

It’s a mammalian innovation, honed and finessed in the latter stages of the Mesozoic era, the so-called Age of Reptiles.

From Slate • Sep. 7, 2024

In this study, Rogers and colleagues performed histological analysis, examining patterns of bone tissue growth in the fossilized leg bones of an array of animals in one of the earliest known Mesozoic ecosystems.

From Science Daily • Apr. 3, 2024

"The most likely cause of death for the female represented by JQ-HX-QW-02 is drowning or exhaustion in relation to mating, constituting the first Mesozoic case of death linked to mating behavior," the authors explain.

From Salon • Feb. 9, 2024

Ma glances at the lush tropical landscape and concludes, “This must be the Mesozoic era. Jurassic or Cretaceous period, I’d say, judging from the flora and fauna. What do you think, Jax?”

From "Dragons in a Bag" by Zetta Elliott