Ancient fossilized lime-sized seeds, amongst the most important within the fossil record, could provide recent insights into the evolution of rainforests in Southeast Asia and Australia. Penn State scientists have identified the fossils as belonging to an extinct genus of legumes closely related to the trendy Castanospermum, the black bean tree, which is now found only in coastal rainforests in northern Australia and nearby islands.
In a report published in International Journal of Plant ScienceAn international team of researchers, including paleontologists from Indonesia, Canada, the United Kingdom and the United States, explained that the fossils present in Kalimantan, Indonesia, date back to the Eocene epoch, about 34 to 40 million years ago.
According to phys.orgThese findings suggest that the ancestors of the black bean tree migrated from Asia to Australia attributable to the collision of tectonic plates, which allowed the exchange of plant and animal species between the continents. This discovery can be the primary macrofossil evidence of plant migration from Asia to Australia after a plate collision, the oldest legume present in the Malay Archipelago, and the primary plant fossil related to the black bean tree.
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Lead creator Edward Spagnuolo of the Department of Geosciences at Pennsylvania State University explained that the fossilized seeds point to the existence of ancient relatives Castanosperma migrated to Australia from Southeast Asia during tectonic collisions and later became extinct in Asia. This hypothesis contrasts with most macrofossil evidence, which normally suggests a migration in the other way.
The researchers noted that the shortage of evidence for migration from Asia to Australia is partly attributable to the poor fossil record within the Malay Archipelago. Spagnuolo added that collecting fossils within the region is notoriously difficult since the surface rocks are sometimes eroded by tropical rains or covered by vegetation and development.
The research team also revealed that paleontological infrastructure within the region may be very limited. They were fortunate to have teamed up with Indonesian paleontologists from the Bandung Institute of Technology, who supported their research.
In 2014, a world team, including Peter Wilf of Penn State, collected fossils from a coal mine in South Kalimantan. The collection included large seeds, pollen samples, leaves, and various fossilized bird tracks and turtle stays.
These seeds are amongst the most important within the fossil record and sure grew in pods that would have reached lengths of as much as 3 feet. After the fossils were collected, they were loaned to Penn State for CT scanning and further evaluation, which revealed similarities to modern Castanosperma.
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The fossil has been named Jantungspermum gunneliithe genus name refers back to the heart-shaped fossil, and the species name honors Gregg Gunnell, the vertebrate paleontologist who led the sphere expedition.
Legumes, of which there at the moment are about 20,000 species, are an incredibly diverse family of flowering plants. Yet this fossil is the one legume identified from Southeast Asia dating back to before the Neogene period.
Wilf added that although tropical regions are probably the most diverse biomes, the fossil record of tropical ecosystem evolution, especially in Asia, stays very sparse. This discovery highlights the necessity for more fossil samples within the Malay Archipelago to fill significant gaps in the worldwide fossil record.
