A fossil dating back many millions of years offers a snapshot of a world where trees may have looked markedly different than the ones that fill forests and line streets today.
Most trees in a fossil record spanning more than 400 million years are found with only their trunks preserved. This rare fossil, however, also contains leaves that reflect the unusual shape of the tree’s canopy. The long, spiky, abundant leaves form a pom-pom-like configuration around the spindly trunk that suggests something out of the whimsical imagination of Dr. Seuss or Avatar CGI artists.
The tree is “a strange growth form in the history of life,” said Robert Gastaldo, a Colby College paleontologist and sedimentologist and co-author of a new study on the discovery published in the journal Current Biology. The tree, named Sanfordiacaulis densifolia, comes from a period in our planet’s history when intact trees remain extremely rare. Plants shed their leaves, branches and reproductive structures, parts that are more decaying and being recycled.
“We can count the number of fossil plant occurrences in the late Paleozoic on one hand where tree trunks are preserved with crown leaves attached,” Gastaldo said in an email.
Scientists found the fossilized tree in New Brunswick, Canada, with more than 250 partially preserved leaves around its trunk, each jutting out about 5.7 feet. The scientists estimate that each leaf grew almost 3.3 feet further before terminating. This means the dense canopy of leaves extended at least 18 feet from spiraling branches around a trunk measuring around 6 inches in diameter.
“Startling to say the least,” said Gastaldo, who compares the look of the tree to an upside-down toilet brush.
‘One Of Evolution’s Experiments’
The tree existed in the “sub-canopy zone” between ground-level plants and taller trees. Its unusual shape allowed it to capture maximum light and reduce competition for resources from groundcover plants below, the researchers say. This strategy suggests plant life in the Early Carboniferous period was more complex than expected, and plants were “experimenting” with different evolutionary forms and growth architectures.
“It is one of evolution’s experiments during a time when forest plants underwent biodiversification, and it is a form that seems to be short lived,” Gastaldo said.
Study co-authors Olivia King and Matthew Stimson found the first fossil of the tree, a partial sample, seven years ago in an active quarry within the Stonehammer UNESCO Global Geopark, site of a rich geologic record. Ensuing years brought the discovery of additional nearby Sanfordiacaulis fossils, which the scientists dated using spores from the enclosing rocks.
The researchers say the fossils survived in such stunning shape due to a catastrophic earthquake that sparked a landslide, which buried and entombed trees and other vegetation along a rift lake. Rift lakes result from when ground sinks due to underground movement.
All but one fossil analyzed for the study currently live at the New Brunswick Museum of Natural History, where they are publicly available for viewing by humans and the Lorax.