Ordovician

American  

[awr-duh-vish-uhn] / ˌɔr dəˈvɪʃ ən /

adjective

1. noting or pertaining to a geologic period of the Paleozoic Era, from 500 million to 425 million years ago, notable for the advent of fish.

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noun

1. the Ordovician Period or System.

Ordovician British  

/ ˌɔːdəʊˈvɪʃɪən /

adjective

1. of, denoting, or formed in the second period of the Palaeozoic era, between the Cambrian and Silurian periods, which lasted for 45 000 000 years during which marine invertebrates flourished

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noun

1. the Ordovician period or rock system

Ordovician Scientific  

/ ôr′də-vĭsh′ən /

1. The second period of the Paleozoic Era, from about 505 to 438 million years ago. During this time most of the Earth's landmasses were gathered in the supercontinent Gondwanaland, located in the Southern Hemisphere. Much of this continent was submerged under shallow seas, and marine invertebrates, including trilobites, brachiopods, graptolites, and conodonts were widespread. The first primitive fishes appeared; some evidence suggests the first land plants may also have appeared at this time. By the end of the Ordovician massive glaciers formed on Gondwanaland, causing sea levels to drop and approximately 60 percent of all known marine invertebrates to become extinct.

2. See Chart at geologic time

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Other Word Forms

• post-Ordovician adjective

Etymology

Origin of Ordovician

1879; after the Ordovices (plural) (< Latin ) an ancient British tribe in N Wales, where rocks characterizing the period were found; see -ian

Example Sentences

Before this fossil was studied, the oldest known chelicerates came from the Early Ordovician Fezouata Biota of Morocco, dating to about 480 million years ago.

From Science Daily • Apr. 3, 2026

It’s possible that the Ordovician craters in Earth’s rock record were created by another astronomical phenomenon, like asteroid debris forming a miniature moon that then broke apart.

From Slate • Oct. 21, 2024

The rings are theorized to have formed 466 million years ago during one of the coldest periods in the planet's history, known as the Ordovician.

From Salon • Sep. 20, 2024

The fossils hail from Morocco’s Fezouata Formation, a deposit dating back to the Early Ordovician period, which began around 488 million years ago and spanned nearly 45 million years.

From New York Times • Mar. 26, 2024

The fight was finally settled in 1879 with the simple expedient of coming up with a new period, the Ordovician, to be inserted between the two.

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