The Paleozoic era's Silurian period saw animals and plants finally emerge on land. But first there was a period of biological regrouping following the disastrous climax to the Ordovician.

However, in 2018 two University of Cambridge scientists named their paper The Silurian hypothesis ... "This short time period raises the obvious question as to whether this could have happened ...

During this period, novel structures such as tracheids ... This group appeared in the late Silurian and persisted into the Late Devonian. Some species, such as Z. shengfengense, are preserved ...