Plant Evolution: When Did Grass Evolve?
http://evolutionarytraits.com/evolution-when-did-grass-evolve/
Grass – ( Poaceae, Gramineae or true Grasses) are a large and nearly ubiquitous family of monocotyledonous flowering plants. Grass has more than 10,000 domesticated and wild species, and represents the fifth-largest plant family on Earth with grasslands alone covering 20% of all vegetation in existence today.
Until recently, fossil findings had indicated that grass had evolved around 55 million years ago. However, recent findings of grass-like phytoliths in Cretaceous dinosaur coprolites have pushed this date back to 65 million years ago.
Grass had been previously thought to be common after the extinction of the dinosaurs, 65 million years ago. It was believed that grass was not an important part of a dinosaurs diet and although fossilised faeces show that they did eat various types of plants, at that time none had then been identified as grass.
However, since the Science Journal study, it has been suggested that grass may have been paramount for these earlier mammals to survive.
Caroline Stromberg from the Swedish Museum of Natural History and her colleagues studied phytoliths (mineral particles produced by grass and other plants), preserved in fossilised dinosaur dung, from central India. The study further suggested grass may have been around a lot longer than previously thought.
The study shed new light on the evolution of grass. Grasses were thought to have undergone a major diversification and geographic proliferation during the so-called Cenozoic, after the dinosaurs had gone extinct.
However, researchers found at least five different types of grass in the fossilised dinosaur droppings, suggesting grasses had already undergone substantial diversification in the late Cretaceous, when dinosaurs still walked the earth.
Many grass types today contain high levels of silica, which makes them tough and hard to chew. One theory proposes that this is an evolutionary defence against being eaten by herbivores.
This defence is traditionally thought to have been a response to large-scale grazing by mammals in the Cenozoic. If this theory is correct. it raises the possibility that grass first began developing this defence in response to grazing by dinosaurs.
Now of course we cannot say yet the exact date in which grass evolved. But pushing the date back another ten-million years sure is a good start to answering many other questions, such as: What other species were reliant on grass for their diet/habitat?
We have so much more to learn about our planet, a limitless supply of discoveries to be made. Each one a passage in their own right to further knowledge, answering the questions – Where did all existence come from? What might happen next |
