In the ancient prehistory of the Earth, there is a chapter waiting to be told known as the Romer Gap. Researchers have identified a gap in the fossil record of tetrapods between 360 million and 345 million years ago, after fish began adapting to land and more than 80 million years before the first dinosaurs appeared.
While mysteries remain about evolution's experiments with living organisms during that 15-million-year gap, the fossilized tree described in a new research paper offers greater insights into some of what was happening during this period in nature's laboratory.
Its name is Sanfordiacolis densifolia, The tree is six inches in diameter and has a trunk about 10 feet long, consisting not of wood, but of vascular plant material, such as a fern. Its crown had more than 200 finely striped compound leaves emerging from branches in a spiral pattern that radiated two and a half feet outward. Robert Gastaldo, professor of geology at Colby College in Maine and author of the study, which was Published Friday in the journal Current Biology, compare it to an “upside-down toilet brush.” It is likely that the top-heavy tree, even the Siosa, was kept upright by intertwining its branches with those of neighboring trees.
“This is a completely new and different type of plant” than what was found in the Late Paleolithic, said Patricia Gensel, a biology professor at the University of North Carolina at Chapel Hill and another author of the study. “We usually get bits and pieces of plants, or metal logs, from the Romer Gap area,” she said. “We don't have many whole plants that we can rebuild. This is what we can.”
The tree was discovered near Valley Waters, New Brunswick, in an active private quarry within Canada. Stonehammer UNESCO Global Geological Survey. (A new fossil museum will open in the village later this year.) The area is part of the 350-million-year-old Albert Formation, a geological layer that has also produced fossilized fish and trace fossils. Although partial fossils of the same tree species have previously been found, the new discovery represents the only fossil whose trunk and crown have been preserved together.
“It's very rare to find something so unique and well-preserved,” said Matt Stimson, an author of the study who works at the University of California, California. New Brunswick Museum who first excavated S. densifolia with another study author, Olivia King of Saint Mary's University. “It's like finding a cactus in the middle of a Canadian boreal forest.”
Trees with spongy, vascularized trunks first appeared 393 to 383 million years ago. Their woody counterparts entered the fossil record about 10 million years later. Logs and trunks make up the bulk of tree fossils from 398 million years to 327 million years ago, and have only been found in coastal wetland areas.
The quarry at Valley Waters was once a tropical swamp ecosystem surrounding a rift lake, a deep body of water extending above a rift zone. Its deposits were similar to those found in modern-day Lake Victoria and Lake Tanganyika in East Africa. The bank containing the tree slid during a catastrophic earthquake, depositing the tree on its side at the bottom of the lake. The ensuing mudslides quickly buried vegetation and wiped out aquatic life. Sediments fill in around the leaves, preserving the three-dimensional shape of the specimen, which lies somewhere on the evolutionary continuum between a woody tree and a megafauna.
S. densifolia evolved during a period when the forest's tiered canopy structure was still developing, and plants were diversifying, Ms. King said. It probably lived under the tallest trees, such as scrub trees over 100 feet tall Lepidodendronbut above low growth lycopods And algae.
“The architecture of this tree suggests that it was growing in this ecological niche of being in the middle of the canopy, trying to capture as much sunlight as possible with branches extending almost as long as the tree was tall,” Ms King said.
“It's an experiment in plant biology that was successful for a while, and then it wasn't,” Dr. Gastaldo said. “We don't see anything like this in any of the forests we've been able to evaluate since.”
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