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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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A new fossil Acmopyle with accessory transfusion tissue and potential reproductive buds: Direct evidence for ever‐wet rainforests in Eocene Patagonia
Abstract PremiseAcmopyle(Podocarpaceae) comprises two extant species from Oceania that are physiologically restricted to ever‐wet rainforests, a confirmed fossil record based on leaf adpressions and cuticles in Australia since the Paleocene, and a few uncertain reports from New Zealand, Antarctica, and South America. We investigated fossil specimens withAcmopyleaffinities from the early Eocene Laguna del Hunco site in Patagonia, Argentina. MethodsWe studied 42 adpression leafy‐shoot fossils and included them in a total evidence phylogenetic analysis. ResultsAcmopyle grayaesp. nov. is based on heterophyllous leafy shoots with three distinct leaf types. Among these, bilaterally flattened leaves uniquely preserve subparallel, linear features that we interpret as accessory transfusion tissue (ATT, an extra‐venous water‐conducting tissue). Some apical morphologies ofA. grayaeshoots are compatible with the early stages of ovuliferous cone development. Our phylogenetic analysis recovers the new species in a polytomy with the two extantAcmopylespecies. We report several types of insect‐herbivory damage. We also transferAcmopyle engelhardtifrom the middle Eocene Río Pichileufú flora toDacrycarpus engelhardticomb. nov. ConclusionsWe confirm the biogeographically significant presence of the endangered West Pacific genusAcmopylein Eocene Patagonia.Acmopyleis one of the most drought‐intolerant genera in Podocarpaceae, possibly due to the high collapse risk of the ATT, and thus the new fossil species provides physiological evidence for the presence of an ever‐wet rainforest environment at Laguna del Hunco during the Early Eocene Climatic Optimum.
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- PAR ID:
- 10508951
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 110
- Issue:
- 8
- ISSN:
- 0002-9122
- Page Range / eLocation ID:
- e16221
- Subject(s) / Keyword(s):
- accessory transfusion tissue (ATT) Acmopyle conifers Early Eocene Climatic Optimum insect damage Laguna del Hunco Podocarpaceae reproductive buds seed cone development total evidence phylogeny
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/ajb2.16221
