Tiny Plant Fossils May Reveal What Earth Looked Like 50 Millions Years Ago

Miniscule, fossilized plants may tell a detailed story of what the Earth looked like 50 million years ago. Researchers have used the clues left in these fossils to find a way to determine the tree cover and density of trees, shrubs and bushes in locations over time.

"Knowing an area's vegetation structure and the arrangement of leaves on the Earth's surface is key for understanding the terrestrial ecosystem," said Regan Dunn, the lead author of the new study, in a news release. "It's the context in which all land-based organisms live, but we didn't have a way to measure it until now."

In this case, the researchers examined fossils found in several sites in Argentina. These fossils represented 38 million years of ecosystem history, starting 49 million years ago.

The researchers already had some idea based on ancient plant remains, such as fossilized pollen and leaves. The team's previous work actually documented vegetation composition for the region. Yet until now, there hasn't been a way to precisely quantify vegetation openness, aside from general speculations of open or bare habitats, as opposed to closed or tree-covered habitats.

The researchers found that cells found in the plant's outermost layer, called the epidermis, change in size and shape depending on how much sunlight the plant is exposed to. These cell patterns could also be found in plant fossils. This, in turn, means that the scientists had a way to tell what vegetation was like in the region.

"Now we have a tool to go and look at a lot of different important intervals in our history where we don't know what happened to the structure of vegetation," said Dunn.

The findings could be huge in determining what ecosystems were like millions of years ago. It could also hint at climate conditions during significant events, such as mass extinctions.

The findings are published in the journal Science.

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