400 million years ago Earth was covered by THIS vegetation

Isn't it wonderful to imagine that Earth was utterly different 400 million years ago! Before the time, when trees, oaks, and bristlecone pines began covering the Earth, towering, tree-like masses named 'Prototaxites' dominated Earth. For the unversed, Prototaxites refers to an extinct genus of terrestrial fungi. These mushroom giants could reach as much as 8 meters in height.
The ancient world of Prototaxites
About 400 million years ago, in the Silurian and Devonian periods, Earth's landscape was not remotely anything like we see today.The land was generally barren because only small plants and invertebrates were just starting to colonize it at that time. In this primitive landscape, Prototaxites dominated as the tallest and most impressive of all living organisms. According to the National Geographic, “The ancient organism boasted trunks up to 24 feet (8 meters) high and as wide as three feet (one meter),” were, quite literally, giants of their time.

Ecological role and importance
Prototaxites provided essential components for highly early ecosystems. According to the Smithsonian, they were decomposers, capable of breaking down organic matter, and recycling nutrients from dead material back into the soil, thus enriching the soil to make it more fertile for other species of plants to eventually evolve and spread. Most probably, giant fungi formed microhabitats that nurtured a wide variety of early life forms.
Fossil evidence and scientific debate
Fossils of Prototaxites had surfaced around the world, casting some light into this earlier, fungal-dominated world. Fossil remains have revealed the incredible complexity of the fungi's anatomy, interwoven tubes that composed their giant trunks. Though it is extremely well-represented in the fossil record, its very nature was the subject of much debate for many years. Some scientists originally thought they might be a kind of lichen or even some incredibly primitive tree.
It was only in 2007 when a study of the carbon isotopes in Prototaxites fossils gave conclusive proof that these structures were, indeed, fungi. This clarifies the role of these fossils in ancient ecosystems and highlights its importance in the history of life on Earth.
The first fossils of Prototaxites were discovered along the shores of Gaspé Bay in Canada by Charles Dawson, a Canadian paleontologist, in 1859. Since then, additional fossils have been found in various parts of the world. These fossils have also been found in Saudi Arabia, which helped scientists further understand the global distribution and significance of Prototaxites.