Permian Tree Fossil Sheds Light on Ancient Evolutionary Race

Prehistoric Flora & Fauna
Curiosities
Thursday, March 11, 2021

Reconstruction of the aerial parts of Paratingia wuhaia from the early Permian of China. Image credit: Yugao Ren / Sijia Tang.

Noeggerathiales are enigmatic plants that existed during Carboniferous and Permian times, 323 to 252 million years ago. Although their diversity and distribution are well known, their place on the plant family tree remained enigmatic because their anatomy was unknown. In new research, paleobiologists in China discovered and reconstructed a new species of noeggerathialean tree that existed 298 million years ago during the Permian period; their analysis shows that Noeggerathiales are more closely related to seed plants than to other fern groups.

“Noeggerathiales were recognized as early as the 1930s, but scientists have treated them as a ‘taxonomic football,’ endlessly kicked around without anyone identifying their place in the Story of Life,” said Dr. Jason Hilton, a paleobiologist at the Institute of Forest Research at the University of Birmingham.

“The spectacular fossil plants found in China are becoming renowned as the plant equivalent of Pompeii.”

“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.”

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

Dr. Hilton and colleagues uncovered the fossilized remains of a new noeggerathialean species — named Paratingia wuhaia — within a 66-cm-thick volcanic ash-fall horizon previously termed the ‘Chinese vegetational Pompeii’ at Wuda open coalmine, Inner Mongolia, China.

They found that Noeggerathiales are in fact advanced tree-ferns that evolved complex cone-like structures from modified leaves.

Despite their sophistication, they fell victim to the profound environmental and climate changes of 251 million years ago that destroyed swamp ecosystems globally.

Paratingia wuhaia: (A) holotype with an entire crown consisting of pseudostrobili and leaves; (B) once-pinnate compound leaf with both large and small pinnules visible; (C) cross-section of a crown illustrating pseudostrobili around the stem; (D) cross-section of pseudostrobilus with microsporangia around the axis with bilateral, inversed Ω-shaped vascular bundle; (E) cross-section of a leaf rachis showing the same form of vascular bundle as that of pseudostrobili axes; (F-H) partial cross, radial, and tangential sections of the stem showing the secondary xylem (wood); (I) tangential section of pseudostrobilus showing sporangial arrangement with single line of megasporangia along with the axis; (J) radial section of pseudostrobilus showing adaxial sporangia and axis lacking nodes; (K) tangential section showing adaxial sporangia and a single line of megasporangia along with the axis; (L) tangential section through same specimen as K showing megasporangial arrangement; (M) detail of the middle part of L showing the megasporangia and microsporangia; (N) single spore macerated from the holotype. Scale bars – 10 cm (A), 3 cm (B), 1 cm (C-E), 100 μm (F), 200 μm (G and H), 5 mm (I-L), 2 mm (M), 10 μm (N). Image credit: Wang et al., doi: 10.1073/pnas.2013442118.

“Many specimens were identified in excavations in 2006-2007 when a few leaves were visible on the surface of the ash,” said Professor Jun Wang, a paleobiologist at the Nanjing Institute of Geology and Palaeontology.

“It looked they might be connected to each other and a stem below — we revealed the crown on site, but then extracted the specimens complete to take them back to the lab.”

“It has taken many years to study these fully and the additional specimens we have found more recently.”

“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 important to science.”

The results were published in the Proceedings of the National Academy of Sciences.

_____

Jun Wang et al. 2021. Ancient noeggerathialean reveals the seed plant sister group diversified alongside the primary seed plant radiation. PNAS 118 (11): e2013442118; doi: 10.1073/pnas.2013442118

Source: www.sci-news.com/