from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Of or belonging to the geologic time, system of rocks, or sedimentary deposits of the second period of the Paleozoic Era, characterized by the appearance of primitive fishes. See Table at geologic time.
- n. The Ordovician Period.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Of a geologic period within the Paleozoic era; comprises lower, middle and upper epochs from about 488 to 443 million years ago.
- proper n. The Ordovician period.
from the GNU version of the Collaborative International Dictionary of English
- adj. Of or pertaining to a division of the Silurian formation, corresponding in general to the Lower Silurian of most authors, exclusive of the Cambrian.
from The Century Dictionary and Cyclopedia
- An epithet applied by C. Lapworth to a series of rocks not capable of exact separation from those underlying or overlying them, either stratigraphically or paleontologically, but which have been the subject of much discussion among English geologists.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. from 500 million to 425 million years ago; conodonts and ostracods and algae and seaweeds
Many crinoids are primarily nocturnal but they are seen during the day with their arms rolled up. living fossil existing virtually unchanged from the ancestors in the geologic age known as the Ordovician Period, but there are many more fossils formed from the Paleozoic Era.
The ancient Ordovician wind carried the first land plant spores to barren and empty places, starting the fantastic unfolding of diversity in plant forms, leading to the first flowering plants roughly 140 million years ago and so on to more than 400,000 species today.
Like I said, he knows more about the Ordovician period than I do, so he was quite content to dig a few holes and admire the clam shells and petrified "seaweed" that we found.
Mason is excited because we might find things that were alive in the Ordovician Period ... and, like, he could instantly name three or four creatures alive then.
That means the rocks are quite a bit older than the Cambrian and Ordovician slate and phyllite at Beavertail, two miles to the southwest.
The package also contained a chunk of Ordovician limestone, riddled with the fossil remains of gastropods and brachiopods, from her backyard near Madison, Wisconsin.
We climbed over the craggy outcrops of Cambro-Ordovician age Fort Burnside Formation and Jamestown Formation, crazily tilted beds of phyllite and slate and siltstone and stark white veins of calcite.
I've been able to determine it came from one of three marines facies, the Galena, Decora, or Platville formations (Middle to Late Ordovician).
(21 May 2010) * In order from oldest to youngest, the extinction events considered by biologists and paleontologists to be the most severe in the earth's history are the Ordovician – Silurian extinction event, the Late Devonian extinction, the Permian – Triassic extinction event, the Triassic – Jurassic extinction event, the Cretaceous – Tertiary extinction event, and the Quaternary-Holocene extinction event (currently underway).
* In order from oldest to youngest, the extinction events considered by biologists and paleontologists to be the most severe in the earth's history are the Ordovician – Silurian extinction event, the Late Devonian extinction, the Permian – Triassic extinction event, the Triassic – Jurassic extinction event, the Cretaceous – Tertiary extinction event, and the Quaternary-Holocene extinction event (currently underway).