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Abstract PremiseAraliaceae comprise a moderately diverse, predominantly tropical angiosperm family with a limited fossil record. Gondwanan history of Araliaceae is hypothesized in the literature, but no fossils have previously been reported from the former supercontinent. MethodsI describe large (to macrophyll size), palmately compound‐lobed leaf fossils and an isolated umbellate infructescence from the early Eocene (52 Ma), late‐Gondwanan paleorainforest flora at Laguna del Hunco in Argentine Patagonia. ResultsThe leaf fossils are assigned to Caffapanax canessae gen. et sp. nov. (Araliaceae). Comparable living species belong to five genera that are primarily distributed from Malesia to South China. The most similar genus is Osmoxylon, which is centered in east Malesia and includes numerous threatened species. The infructescence is assigned to Davidsaralia christophae gen. et sp. nov. (Araliaceae) and is also comparable to Osmoxylon. ConclusionsThe Caffapanax leaves and Davidsaralia infructescence, potentially representing the same source taxon, are the oldest araliaceous macrofossils and provide direct evidence of Gondwanan history in the family. The new fossils and their large leaves enrich the well‐established biogeographic and climatic affinities of the fossil assemblage with imperiled Indo‐Pacific, everwet tropical rainforests. The fossils most likely represent shrubs or small trees, adding to the rich record of understory vegetation recovered from Laguna del Hunco.
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This content will become publicly available on May 8, 2026
Fossils of an endangered, endemic, giant dipterocarp species open a historical portal into Borneo's vanishing rainforests
Abstract PremiseAsia's wet tropical forests face a severe biodiversity crisis, but few fossils record their evolutionary history. We recently discovered in situ cuticles on fossil leaves, attributed to the giant rainforest treeDryobalanopsof the iconic Dipterocarpaceae family, from the Plio‐Pleistocene of Brunei Darussalam (northern Borneo). Studying these specimens allowed us to validate the generic identification and delineate affinities to living dipterocarp species. MethodsWe compared the leaf cuticles and architecture of these fossil leaves with the seven livingDryobalanopsspecies. ResultsThe cuticular features shared between the fossils and extantDryobalanops, including the presence of giant stomata on veins, confirm their generic placement. The leaf characters are identical to those ofD. rappa, an IUCN red‐listed Endangered, northern Borneo endemic. TheD. rappamonodominance at the fossil site, along withDipterocarpusspp. leaf fossils, indicates a dipterocarp‐dominated forest near the mangrove‐swamp depocenter, most likely in an adjacent peatland. ConclusionsTheDryobalanops rappafossils are the first fossil evidence of a living endangered tropical tree species and show how analysis of in situ cuticles can help illuminate the poorly known floristic history of the Asian tropics. This discovery highlights new potential for fossils to inform heritage values and paleoconservation in Southeast Asia.
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- Award ID(s):
- 1925755
- PAR ID:
- 10589834
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 112
- ISSN:
- 0002-9122
- Page Range / eLocation ID:
- e700361
- Subject(s) / Keyword(s):
- Asian rainforests Borneo cuticles Dipterocarpaceae endangered species paleobotany peatlands
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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