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Key Evolutionary Plant Link Found Fossilized in Volcanic Ash

Fossilized plant specimens found in volcanic ash in China helped researchers find a link between fern and seed plants in the prehistoric world.

(CN) — Fossils found in volcanic ashfall at a site researchers call the “Pompeii of prehistoric plants” that date back to 300 million years ago reveal for the first time that seed plants grew out of a highly evolved lineage of peat-forming plant.

An international research team led by paleontologists at China’s Nanjing Institute of Geology and Paleontology and the United Kingdom’s University of Birmingham published a report Monday on the importance of these now-extinct plants, called Noeggerathiales, in the journal Proceedings of the National Academy of Sciences.

They say the plant fossils that were found fully preserved in the Chinese region of Inner Mongolia are from around 325 to 251 million years ago.

This discovery helped researchers understand that Noeggerathiales are more closely related to the later developing seed plants than to other fern groups, according to the study.

Once believed to be “an evolutionary dead-end,” Noeggerathiales are now recognized as advanced tree-ferns that developed complex cone-like structures from modified leaves, the researchers say.  

But despite their evolutionary sophistication, the study says Noeggerathiales were wiped out 251 million years ago by rapid and extreme environmental change that destroyed swamp ecosystems worldwide.

Jason Hilton with the University of Birmingham’s Institute of Forest Research, who co-authored the study, said Noeggerathiales might serve as a cautionary tale today.

“The fate of Noeggerathiales is a stark reminder of what can happen when even very advanced life forms are faced with rapid environmental change,” Hilton said in a statement.  

“The spectacular fossil plants found in China are becoming renowned as the plant equivalent of Pompeii,” he added. “Thanks to this slice of life preserved in volcanic ash, we were able to reconstruct a new species of Noeggerathiales that finally settles the group’s affinity and evolutionary importance.”

Hilton said Noeggerathiales were recognized as early as the 1930s but that their evolutionary importance has only now been discovered.

The study was made possible after researchers discovered complete Noeggerathiale fossils preserved in a bed of volcanic ash about 2 feet thick that formed 298 million years ago and smothered all plants growing in a nearby swamp. The ash preserved many complete individual plants in microscopic detail.

Jun Wang, professor of palaeobotany at the Nanjing Institute of Geology and Paleontology and lead author of the study, said many Noeggerathiales specimens were identified in excavations in 2006 and 2007 when a few leaves were identified on the surface of the ash.

“It looked like they might be connected to each other and a stem below,” Wang said in a statement. “We revealed the crown on site, but then extracted the specimens complete to take them back to the lab.”

Wang said study of these specimens has gone on for years and that the newly discovered complete fossils helped the study tremendously.

“The complete trees are the most impressive fossil plants I have seen, and because of our careful work, they are also some of the most impressive to science,” Wang said.

From this discovery, researchers concluded that the ancestral lineage from which seed plants evolved diversified during the Devonian, Carboniferous and Permian periods, and did not rapidly die out as was previously thought. 

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