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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. 

Abstract PremiseFossil infructescences and isolated fruits with characters of Malvoideae, a subfamily of Malvaceae (mallow family), were collected from early Eocene sediments in Chubut, Argentina. The main goals of this research are to describe and place these fossils systematically, and to explore their biogeographical implications. MethodsFossils were collected at the Laguna del Hunco site, Huitrera Formation, Chubut, Patagonia, Argentina. They were prepared, photographed, and compared with extant and fossil infructescences and fruits of various families using herbarium material and literature. ResultsThe infructescences are panicles with alternate arrangement of fruits. They bear the fruits on short pedicels that are subtended by a bract; the fruits display an infracarpelar disk and split to the base into five ovate sections interpreted as mericarps. Each mericarp is characterized by an acute apex and the presence of a longitudinal ridge. The isolated fruits show the same features as those on the infructescences. The fossils share unique features with members of the cosmopolitan family Malvaceae, subfamily Malvoideae. ConclusionsThe fossils have a unique combination of characters that does not conform to any previously described genus, justifying the erection of a new genus and species,Uiher karuen. This new taxon constitutes the first known Malvoideae reproductive fossils of the Southern Hemisphere, expanding the distribution of Malvoideae during the early Eocene. 

Summary The tall eucalypt forests (TEFs) of the Australian tropics are often portrayed as threatened by ‘invasive’ neighboring rainforests, requiring ‘protective’ burning. This framing overlooks that Australian rainforests have suffered twice the historical losses of TEFs and ignores the ecological and paleobiological significance of rainforest margins. Early Eocene fossils from Argentina show that biodiverse rainforests with abundantEucalyptusexisted > 50 million years ago (Ma) in West Gondwana, shaped by nonfire disturbance factors such as landslides and volcanic flows. Humid volcanic environments with eucalypts were also present in eastern Australia over much of the Cenozoic. The dominance of fire‐adapted eucalypts appears to be geologically recent and is linked to Neogene C₄grassland expansion, Pleistocene climate cycles, and human activity. We suggest that characterizing TEFs and rainforests as adversarial results from misinterpreting the evolutionary history and expansion‐contraction dynamics of a single humid forest system, whose features are now heavily modified by human activities. The resulting management practices damage the outstanding World Heritage values and carbon storage of affected areas and thus have impacts far beyond Australia. The fossil evidence shows that rainforest margins preserve ancient, still evolving, and globally significant forest interactions that should be prioritized for restoration and research. 

Abstract Caldera lake sediments of the early Eocene Tufolitas Laguna del Hunco (Chubut Province, Argentina) host one of the world’s best-preserved and most diverse fossil plant assemblages, but the exceptional quality of preservation remains unexplained. The fossils have singular importance because they include numerous oldest and unique occurrences in South America of genera that today are restricted to the West Pacific region, where many of them are now vulnerable to extinction. Lacustrine depositional settings are often considered optimal for preservation as passive receptors of suspended sediment delivered, often seasonally, from lakeshores. However, caldera lakes can be influenced by a broader range of physical and chemical processes that enhance or decrease fossil preservation potential. Here, we use Laguna del Hunco to provide a new perspective on paleoenvironmental controls on plant fossil preservation in tectonically active settings. We establish a refined geochronological framework for the Laguna del Hunco deposits and present a detailed history of processes active during ∼ 200,000 years of lake filling from 52.217 ± 0.014 Ma to 51.988 ± 0.035 Ma, the time interval that encompasses nearly all fossil deposition. Detailed facies analysis shows that productive fossil localities reside within high-deposition-rate beds associated with high-energy density flows and wave-reworked lake-floor sediments, challenging traditional views that low-energy environments are required for well-preserved plant fossils. These results demonstrate that even delicate fossil components like fruits and flowers can survive high-energy transport, underscoring the importance of rapid burial as a primary control on fossil preservation. Short, steep sediment-transport networks may facilitate terrestrial fossil preservation by limiting opportunities for biochemical degradation on land and providing relatively frequent, high-energy depositional events, which quickly transport and bury organic material following events such as landslides from steep, wet, surrounding slopes. Our new model for plant taphonomy opens a path toward finding and understanding other exceptional biotas in environments once considered unlikely for preservation. 

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. 

Summary Fossilized plant–insect herbivore associations provide fundamental information about the assembly of terrestrial communities through geologic time. However, fossil evidence of associations originating in deep time and persisting to the modern day is scarce.We studied the insect herbivore damage found on 284Eucalyptus frenguellianaleaves from the early Eocene Laguna del Hunco rainforest locality in Argentinean Patagonia and compared damage patterns with those observed on extant, rainforest‐associatedEucalyptusspecies from Australasia (> 10 000 herbarium sheets reviewed).In the fossil material, we identified 28 insect herbivory damage types, including 12 types of external feeding, one of piercing‐and‐sucking, five of galls, and 10 of mines. All 28 damage types were observed in the herbarium specimens.The finding of all the fossil damage types on extantEucalyptusspecimens suggests long‐standing associations between multiple insect herbivore lineages and their host genus spanning 52 million years across the Southern Hemisphere. This long‐term persistence, probably enabled through niche conservatism in wet eucalypt forests, demonstrates the imprint of fossil history on the composition of extant insect herbivore assemblages. Although the identities of most insect culprits remain unknown, we provide a list ofEucalyptusspecies and specific population locations to facilitate their discovery, highlighting the relevance of fossils in discovering extant biodiversity. 

Summary Many tree genera in the Malesian uplands have Southern Hemisphere origins, often supported by austral fossil records. Weathering the vast bedrock exposures in the everwet Malesian tropics may have consumed sufficient atmospheric CO₂to contribute significantly to global cooling over the past 15 Myr. However, there has been no discussion of how the distinctive regional tree assemblages may have enhanced weathering and contributed to this process. We postulate that Gondwanan‐sourced tree lineages that can dominate higher‐elevation forests played an overlooked role in the Neogene CO₂drawdown that led to the Ice Ages and the current, now‐precarious climate state. Moreover, several historically abundant conifers in Araucariaceae and Podocarpaceae are likely to have made an outsized contribution through soil acidification that increases weathering. If the widespread destruction of Malesian lowland forests continues to spread into the uplands, the losses will threaten unique austral plant assemblages and, if our hypothesis is correct, a carbon sequestration engine that could contribute to cooler planetary conditions far into the future. Immediate effects include the spread of heat islands, significant losses of biomass carbon and forest‐dependent biodiversity, erosion of watershed values, and the destruction of tens of millions of years of evolutionary history. 

Abstract The Cretaceous–Paleogene (K–Pg) mass extinction was geologically instantaneous, causing the most drastic extinction rates in Earth’s History. The rapid species losses and environmental destruction from the Chicxulub impact at 66.02 Ma made the K–Pg the most comparable past event to today’s projected “sixth” mass extinction. The extinction famously eliminated major clades of animals and plankton. However, for land plants, losses primarily occurred among species observed in regional studies but left no global trace at the family or major-clade level, leading to questions about whether there was a significant K–Pg plant extinction. We review emerging paleobotanical data from the Americas and argue that the evidence strongly favors profound (generally >50%), geographically heterogeneous species losses and recovery consistent with mass extinction. The heterogeneity appears to reflect several factors, including distance from the impact site and marine and latitudinal buffering of the impact winter. The ensuing transformations have affected all land life, including true angiosperm dominance in the world’s forests, the birth of the hyperdiverse Neotropical rainforest biome, and evolutionary radiations leading to many crown angiosperm clades. Although the worst outcomes are still preventable, the sixth mass extinction could mirror the K–Pg event by eliminating comparable numbers of plant species in a geologic instant, impoverishing and eventually transforming terrestrial ecosystems while having little effect on global plant-family diversity. 

PremiseSolanaceae is a scientifically and economically important angiosperm family with a minimal fossil record and an intriguing early evolutionary history. Here, we report a newly discovered fossil lantern fruit with a suite of features characteristic of Physalideae within Solanaceae. The fossil comes from the early Eocene Laguna del Hunco site (ca. 52 Ma) in Chubut, Argentina, which previously yielded the only other physaloid fruit fossil,Physalis infinemundi. MethodsThe fruit morphology and calyx venation pattern of the new fossil were compared withP. infinemundiand extant species of Solanaceae. ResultsPhysalis hunickeniisp. nov. is clearly distinct fromP. infinemundiin its fruiting calyx with wider primary veins, longer and thinner lobes, and especially in its venation pattern with high density, transverse tertiary veins; these features support its placement in a new species. In comparison with extant physaloid genera, the calyx venation pattern and other diagnostic traits reinforce placement of the new fossil, likeP. infinemundi, within the tribe Physalideae of Solanaceae. ConclusionsBoth species of fossil nightshades from Laguna del Hunco represent crown‐group Solanaceae but are older than all prior age estimates of the family. Although at least 20 transoceanic dispersals have been proposed as the driver of range expansion of Solanaceae, the Patagonian fossils push back the diversification of the family to Gondwanan times. Thus, overland dispersal across Gondwana is now a likely scenario for at least some biogeographic patterns, in light of the ancient trans‐Antarctic land connections between South America and Australia. 

Summary Fossil discoveries can transform our understanding of plant diversification over time and space. Recently described fossils in many plant families have pushed their known records farther back in time, pointing to alternative scenarios for their origin and spread.Here, we describe two new Eocene fossil berries of the nightshade family (Solanaceae) from the Esmeraldas Formation in Colombia and the Green River Formation in Colorado (USA). The placement of the fossils was assessed using clustering and parsimony analyses based on 10 discrete and five continuous characters, which were also scored in 291 extant taxa.The Colombian fossil grouped with members of the tomatillo subtribe, and the Coloradan fossil aligned with the chili pepper tribe. Along with two previously reported early Eocene fossils from the tomatillo genus, these findings indicate that Solanaceae were distributed at least from southern South America to northwestern North America by the early Eocene.Together with two other recently discovered Eocene berries, these fossils demonstrate that the diverse berry clade and, in turn, the entire nightshade family, is much older and was much more widespread in the past than previously thought.