Tudenanian

The Tudenanian Period is the second period of the Promesolithic Era, lasting from 490 to 420 million years. It is named after the Tudenan of northeastern Eldham, as it is on their lands that the first rocks of this era were identified by scientists.

The end of the Tudenanian would experience the first mass extinction of the Promesolithic, as many older marine organisms (including orthoceratid and barocorythine mollusks) would die off. Still, the period itself is considered a high point in marine biodiversity, especially considering how young many animal phyla were at the time. The first land plants appeared during this time, as green algae spores similar to modern mosses show up in terrestrial sediments about 460 million years ago. They were probably very simple, without vascular systems or seeds.