ordovician period
Proper noun * The Ordovician Period: A major division of geologic time, the second period of the Paleozoic Era, following the Cambrian Period and preceding the Silurian Period. It is characterized by the diversification of marine life, including the proliferation of invertebrates like brachiopods and trilobites, the appearance of the first vertebrates (jawless fish), and extensive shallow seas covering many continents.
The term "Ordovician Period" is used as a proper noun to refer to this specific interval in Earth's history. It is always capitalized. * The Ordovician Period saw a dramatic increase in the diversity of marine organisms. * Fossils from the Ordovician Period are commonly found in limestone formations. * Geologists study rock layers to understand the climate changes during the Ordovician Period.
- In formal/scientific context: The term is used precisely to denote the time span from approximately 485.4 to 443.8 million years ago.
- The boundary between the Ordovician and Silurian periods is marked by a major extinction event.
- As an adjective (Ordovician): The word "Ordovician" alone can function as an adjective to describe things from this period.
- Ordovician rocks | Ordovician fauna | an Ordovician shale deposit
- Ordovician (adjective/noun): Pertaining to the Ordovician Period; also used informally to refer to the period itself.
- The Ordovician was a time of great evolutionary change.
- Late/Early/Middle Ordovician: Subdivisions of the period used for more precise dating.
- This fossil is characteristic of the Late Ordovician.
As a proper noun referring to a specific geologic time unit, "Ordovician Period" does not have other common meanings. Its definition is strictly historical and scientific.
- Ordovician (when used as a noun to refer to the period)
- There are no true conceptual synonyms, but it can be described as:
- The second period of the Paleozoic Era
There are no common idioms using "Ordovician Period."
There are no phrasal verbs using "Ordovician Period."
- from 500 million to 425 million years ago; conodonts and ostracods and algae and seaweeds