Newly discovered fossilized pollen spores suggest that modern plant life evolved earlier than previously thought, researchers report online April 17 in Science.
Until now, the earliest fossil evidence of vascular land plants — plants with special tissues to efficiently transport water, minerals and food — came from the early Silurian period, which started about 444 million years ago. Now, fossils have been found that show vascular land plants existed in the mid to late Ordovician period, as early as 450 million years ago, the scientists say.
It’s widely believed that the earliest land plants were mosslike and, in lieu of vascular tissues, absorbed water and minerals and then passed them among unspecialized cells. Scientists think that once vascular plants appeared, the more modern plants swiftly dominated more primitive plant life. But if vascular plants evolved earlier, as the new research suggests, then “it appears they did not colonize the planet extremely quickly, as previously thought,” says study coauthor Charles Wellman of the University of Sheffield in the United Kingdom.
Wellman and his colleagues found the fossilized remains of ornamented trilete spores in rock cores drilled from northern Saudi Arabia. “Trilete spores are believed to derive from vascular plants,” Wellman says.
But an earlier start for vascular plants isn’t the only explanation for the findings, contends Paul Strother of the Weston Observatory of Boston College in Weston, Mass. “Ornamented trilete spores could also come from [even] earlier types of plants, not just vascular plants.” .