What are the Oldest Land Plants?

The earliest evidence for the oldest land plants appears as small tetrad spores dated to 470 million years ago, from the mid-Ordovician period. These came from mosses and lichens. At the time, the land would have been mostly desolate, covered in deserts and badlands, with little greenery to be seen except for algae on the margins of streams and ponds. Green algae took the first steps onto the land, and it is from green algae that all land plants are thought to have evolved. This idea is supported by genetic and morphological studies. At first, all land plants were bryophytes (non-vascular), meaning they lacked specialized tissues to transport water and nutrients, found in most modern plants. These plants had to suck their nutrients directly from the environment or die trying. An early ally of the algal pioneers, the ancestors of the oldest land plants, were fungi, whose hyphae (fungal hairs) are found intermixed with these fossils. That is what a lichen is -- a close symbiotic relation ... more