Fossil leaves found in Brunei belong to Dryobalanops rappa, a living tree known as Kapur Paya and described in the study as endangered. The fossils are most likely Plio-Pleistocene in age. Penn State summarized them as at least two million years old, but the study does not give an exact date for the leaves.
How old are the Borneo tree fossils?
The 2025 study assigns the fossil flora to the Plio-Pleistocene and describes that age as the most likely interpretation. Penn State’s May 8, 2025, announcement called the fossils at least two million years old. That phrase is a broad summary, not an exact date established for these particular leaves.
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The fossils came from an unnamed rock unit overlying the late Miocene Miri Formation. Palynological evidence allows a broad potential age range, while the study treats a Plio-Pleistocene age as most likely.
What is the Kapur Paya tree?
Kapur Paya is the local name for Dryobalanops rappa, a living dipterocarp tree endemic to northern Borneo. The study describes it as an IUCN red-listed Endangered species and reports that it forms dominant stands in regional peatlands. This is the conservation classification reported by the paper.
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Where were the fossils found?
The key leaves were collected at Kampong Lugu in Tutong District, Brunei Darussalam, on the northern part of Borneo. They are leaf compressions from a mangrove-swamp depositional setting. Together with other dipterocarp leaves in the assemblage, they indicate a dipterocarp-dominated forest near the swamp, probably on adjacent peatland.
A separate Dryobalanops leaf without preserved cuticle was reported from Berakas Beach, but the species-level identification of D. rappa rests on the Kampong Lugu material.
How did scientists identify the fossil leaves?
Earlier fossil leaves had been identified as Dryobalanops from their overall leaf architecture. That evidence alone is not conclusive: densely spaced secondary veins also occur in unrelated plant families. The 2025 team examined preserved cuticles as well as leaf shape and venation, then compared the fossils with all seven living Dryobalanops species.
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- Cuticle and leaf features shared with living Dryobalanops supported the genus identification.
- The fossil leaf characters matched D. rappa.
- The paper highlights giant stomata on veins among the diagnostic cuticle features.
This was a morphological identification, not a DNA-based one. The preserved cuticle strengthened the identification beyond what architecture alone could establish.
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Why does this fossil discovery matter?
The authors describe the find as the first fossil evidence of a living endangered tropical tree species and the first unequivocal fossil record of Dryobalanops leaves. It documents a long history for a tree still found in Borneo and adds evidence for reconstructing the region’s rainforest past. Peter Wilf, a co-author and professor of geosciences, said the fossils provide “a vital historical foundation for conserving tropical Asia’s keystone trees.”
The fossil record offers historical context and heritage value; it does not by itself establish a specific conservation policy or show that Borneo’s modern forests have remained unchanged. More broadly, fossil leaves are rarely found in wet tropical regions, where dense forest cover and deeply weathered soils can obscure rock exposures.
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