Paleontologists have determined that a mysterious fruit first discovered in the 1970s is the oldest known frankincense fossil. Scale bar = 2 mm.
Credit: Stephen Manchester
Mysterious fossils discovered in India in the 1970s have been identified as part of the Frankincense family, suggesting a Southern Hemisphere origin and reshaping our understanding of plant evolution. In the early 1970s, paleontologists working on the outskirts of an Indian village discovered tiny bead-like fossils embedded in the gray chert that dotted the surrounding fields. The site was notorious for the discovery of hard-to-identify plant fossils, including the fruits of extinct creatures. The fossils have been named “Enigmocarpon”.
The new fossils proved to be similarly frustratingly unwieldy. More plants were discovered in India in subsequent decades, but scientists were unable to determine which type of plant they belonged to.
A breakthrough in fossil identification: Now, researchers say they have solved the mystery. Stephen Manchester, curator of paleobotany at the Florida Museum of Natural History, used CT scanning technology to create his 3D reconstructions of the original fossil specimens and other specimens collected since then. He showed this to his colleagues and noticed something strange about his five triangular seeds inside.
Before the widespread use of CT scans in paleontology, these small fossils, less than 10 mm in diameter, were particularly difficult to study and identify. “When I showed him the 3-D images, he said, ‘Those aren’t seeds. They’re pyrenes,'” Manchester said with Walter Judd, curator of botany at the Florida Museum. I remembered the conversation. Pyrene is a woody dispersal pod that provides an additional layer of protection to the seeds. Distinguishing between seeds and pyrenes requires close scrutiny, especially when they are the size of a snowflake.
“If we had a specimen that broke in just the right plane, we would have been able to identify it, but we couldn’t identify it with the material we had,” Manchester said. Although they may look like seeds, these woody structures are actually pyrenes, similar to the stones found in peaches and date palms.
Frankincense family connection: Only a few plant groups produce pyrene, and even fewer have fruits containing five seeds arranged in a pentagram. Through a process of elimination, Manchester and Judd determined that the fossils belonged to the frankincense family, an extinct member of the Kansas family. Fossilized trees, leaves, fruits, and flowers of this family have been found elsewhere in India, often sandwiched between thick basalt slabs created by the largest volcanic eruptions in Earth’s history.
Geological background and importance: At that time, India was an island off the southeast coast of Africa. India’s continental plate slowly moved toward Europe and Asia, breaking the seal of a thin layer of Earth’s crust as it passed through Madagascar. The fossils were preserved during a quiet period between eruptions, which makes it the oldest fossil of the Kansidae family ever discovered, and has important implications for the origin of the family. Scientists have a good idea of when this group of plants first evolved, but it’s still unclear where they came from.
Source: scitechdaily.com
