True grasses of the family Poaecae are a late product of plant evolution, but not as late as was previously thought. They seem to have existed as early as Late Cretaceous, according to some grass-like phytoliths found in 66-million-year-old coprolite, or dinosaur dung, and pollen record on several continents.
However, the vast grasslands known today have not existed for long. For 25 million years or so after the demise of non-avian dinosaurs, grasses account for less than 1 % of all pollen in the fossil record. Grasslands only appeared after the global rainforests of Eocene Epoch receded, making way to dry-adapted plants like grasses. Evidence of large grass-dominated ecosystems appears by the Early Miocene, some 20 million years ago. (photo: Miroslav Duchacek/Wikimedia Commons)
Despite the lack of actual grasses, there is a number of other, older plants that look very grass-like even though they’re not closely related. Paleoartists often avoid depicting anything that looks remotely like a grass, but the general shape – thin leaves and/or fronds standing more or less upright, with reproductive structures on top – is fairly common and seems to work for both xeric and mesic plants. Continue reading