Ordovician - Wikipedia
In the Middle Ordovician, the trilobite-dominated Early Ordovician communities were replaced by generally more mixed ecosystems, in which brachiopods, bryozoans, molluscs, cornulitids, …
Ordovician Period | Major Events, Extinction, & Facts | Britannica
2024年12月24日 · The Ordovician is divided into three epochs: Early Ordovician (485.4 million to 470 million years ago), Middle Ordovician (470 million to 458.4 million years ago), and Late …
The Ordovician Period - University of California Museum of …
By the Middle Ordovician North America had shed its seas and a tectonic highland, roughly corresponding to the later Appalachian Mountains, formed along the eastern margin of the …
Ordovician Period—485.4 to 443.8 MYA - U.S. National Park Service
2023年4月28日 · A change in plate motion during the middle of the Ordovician Period set the stage for the ensuing mountain-building event. Moreover, the ocean to the east, which …
Ordovician Period Information and Facts - National Geographic
During the Ordovician period, part of the Paleozoic era, a rich variety of marine life flourished in the vast seas and the first primitive plants began to appear on land—before the second largest...
Ordovician Period - Natural History Museum
2012年8月10日 · The Ordovician ended with the second greatest extinction event of the Phanerozoic Eon. Two massive reductions, a million years apart, created this event—resulting …
The Middle Ordovician - Palaeos
The Middle Ordovician includes the Dapingian (Middle Arenig) and Darriwilian Late Arenig, Llanvirn and Llandeilo) Ages. Historically, it has been the most difficult and contentious …
Ordovician period - Geology Page
2014年3月2日 · The Ordovician Period in Britain was traditionally broken into Early (Tremadocian and Arenig), Middle (Llanvirn [subdivided into Abereiddian and Llandeilian] and Llandeilo) and …
Ordovician - New World Encyclopedia
It was long thought that the first true chordates appeared in the Ordovician period in the form of fossils of the fish-like Ostracoderms found in strata traced to the Middle Ordovician (Gregory …
Plant Evolution & Paleobotany - Middle Ordovician
The Middle Ordovician (470-459 Ma) is a time period that occurs after the Floian (Early Ordovician), and before the Sandbian (Late Ordovician)