More Plants Survived the World’s Greatest Mass Extinction Than Thought

A mummified seed-fern frond flaking off a piece of mudrock after being exposed to the light of day for the first time in some 255 million years; well-preserved fossils like this from Permian sedimentary rocks exposed along the shore of the Dead Sea shed new light on the early origins of major seed-plant lineages. Credit: Palaeobotany Research Group

Several new plant fossils from present-day Jordan push back the ages of important seed plant lineages, suggesting these lineages survived the mass extinction event at the end of the Permian. Discovery of these fossils - remarkably preserved in a region where fossils are hard to come by - also point to this Permian-age tropical habitat as a "hidden cradle" of plant evolution and provides evolutionary examples of major seed-plant lineages, including the eldest ancestor of modern pine trees.

According to the report, the finds offer a rare glimpse into the early origins of the seed-bearing lineages that would eventually become Mesozoic Earth's dominant forms of plant life. Today's tropical environments host the planet's greatest biodiversity - much like they did in epochs past - and are considered by some to be important centers of early biological diversification compared to regions at higher latitudes.

While hypotheses to date to explain the rich biodiversity of life in the tropics include the idea that ancient equatorial ecosystems served as so-called "evolutionary cradles," generating novel lineages at higher rates, to what degree this was so has been controversial. This uncertainty is due in large part to a lack of paleobotanical evidence from these regions because the drought-prone tropical habitats rarely preserve fossils.

However, Patrick Blomenkemper and colleagues report on the discovery of an exceptionally preserved assemblage of late-Permian plant fossils exposed on the eastern shore of the Dead Sea. The diverse collection of fossils - more than 250 million years old - yields the earliest records of three major seed-plant lineages including Podocarpaceae - the second largest family of living conifers.

According to Blomenkemper et al., the findings indicate that drought-prone tropical habitats did serve as evolutionary cradles for early plant diversification. What's more, the authors note that these plant lineages appear to have survived the mass extinction event that marked the end of the Permian. The results suggest that land plants, and perhaps the communities they supported, were more resilient than previously believed.

The above story is based on materials provided by the American Association for the Advancement of Science.

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