Let's be honest; life began on land.  I know, I know, that is blasphemy and Neil Shubin will stand on high and strike me down with my inner fish for saying such a thing, but while life began in water, life began on land.   

And that took land plants.  Thanks, embryophytes!

Generally, I have never cared much about plants.  I am kind of an anti-vegetarian in the sense that I don't eat plants, instead I regard plants as those things food eats in order to become bigger food.  I get the importance of plants scientifically, though.

In that respect, that ol' demon on the edge of existence just got pushed back in time a little farther.   Researchers writing in New Phytologist found primordial spores from 473 million years ago in the central Andes of Argentina, what was then in the east of the Gondwana continent, one of two supercontinents then.   Here's a Wiki pic from 200 million years ago:

Laurasia-Gondwana

These embrophytes mean the date of the first land plants is farther back than the previous Darriwilian cryptospores found in Saudi Arabia and Czech Republic - western Gondwana then.   So the researchers hypothesize that land plants evolved in the eastern part of Gondwana and palynological samples back them up, at least for now.

The fossils represented five genera which means diversification had occurred earlier, though how much earlier is a science mystery still waiting to be solved.   

Citation: C. V. Rubinstein, P. Gerrienne, G. S. De La Puente, R. A. Astini, P. Steemans, 'Early Middle Ordovician evidence for land plants in Argentina (eastern Gondwana)', New Phytologist Volume 188, Issue 2, pages 365–369, October 2010 DOI: 10.1111/j.1469-8137.2010.03433.x

but The invasion of the land by plants: when and where? by Charles H. Wellman is free to read.