Middle Ordovician

Great Ordovician Biodiversity Event

The Middle Ordovician (470-459 Ma) is a time period that occurs after the Floian (Early Ordovician), and before the Sandbian (Late Ordovician)

Flora (plants, fungi, bacteria)

The earliest unambiguous indirect fossil evidence of land plants can be traced to Dapingian, which is represented by dyads and tetrahedral tetrads (microfossils) from the Gondwana paleo-continent
Potential but controversial macrofossils of bryophytes from the late Middle Ordovician (Darriwilian) of Tennessee (Retallack, 2019)
- Liverworts, mosses, and hornworts are all present at the site
Plant life existed on the margins of the land in the Dapingian
- By the Darriwilian, plants lived along river valleys and flood plains, far from open water
Fossilized fungi hyphae have been recovered from the middle Ordovician of Wisconsin
- These were mycorrhizal fungi: symbiotic fungi serve as or are associated with, plants (Redecker et al., 2000)
- Retallack (2019) also reports endomycorrhiza, named Paleoglomus, and a foot-tall member of the nematophyte Prototaxites
- This suggests plants were growing in regions where they were not covered with water and therefore required a method of extracting minerals from primitive soils, at least for substantial periods of time

Fauna

Great Ordovician Biodiversity Event (GOBE)
- Explosion of invertebrate life
- Evidence of very early vertebrates

Geophysical

Strange impact craters were found during this time; Earth may have had a temporary ring system (Tomkin et al., 2024)
- Shading of Earth by the ring may have triggered a global icehouse period.