Search

The most common macrofossils in the highly diverse flora from Laguna del Hunco (early Eocene of Chubut, Argentina) are "Celtis" ameghinoi leaves, whose true affinities have remained enigmatic for a century. The species accounts for 14% of all plant fossils in unbiased field counts and bears diverse insect-feeding damage, suggesting high biomass and paleoecological importance. The leaves have well-preserved architecture but lack cuticles or reproductive attachments. We find that the fossils only superficially resemble Celtis and comparable taxa in Cannabaceae, Ulmaceae, Rhamnaceae, Malvaceae, and many other families. However, the distinctive foliar morphology conforms in detail to Dobinea (Anacardiaceae), a genus with two species of shrubs and large herbs ranging from India's Far East and Tibet to Myanmar and central China, and we propose Dobineaites ameghinoi (E.W. Berry) gen. et comb. nov. for the fossils. This discovery strengthens the extensive biogeographic links between Eocene Patagonia and mainland Asia, provides the first fossil record related to Dobinea, and represents a rare Gondwanan macrofossil occurrence of Anacardiaceae, which was widespread and diversified in the Northern Hemisphere at the time. The diverse leaf architecture of Anacardiaceae includes several patterns usually associated with other taxa, and many other leaf fossils in this family may remain misidentified. Los macrofósiles más comunes en la flora altamente diversa de la Laguna del Hunco (Eoceno temprano de Chubut, Argentina) son hojas de "Celtis" ameghinoi, conocidas desde hace un siglo y cuyas afinidades han sido enigmáticas. La especie representa el 14% del total de las hojas fósiles en censos imparciales de campo, y los ejemplares exhiben diversos daños producidos por alimentación de insectos, lo que sugiere que habrían tenido elevada biomasa e importancia ecológica. Las hojas presentan la arquitectura bien conservada, pero carecen de cutículas o conexiones con estructuras reproductivas. Encontramos que los fósiles sólo se parecen superficialmente a Celtis y a taxones comparables de Cannabaceae, Ulmaceae, Rhamnaceae, Malvaceae, y muchas otras familias. Sin embargo, la morfología foliar distintiva se ajusta en detalle a Dobinea (Anacardiaceae), un género con dos especies de arbustos y grandes hierbas que se distribuye desde el Oriente de la India y el Tíbet hasta Myanmar y China central. Proponemos Dobineaites ameghinoi (E.W. Berry) gen. et comb. nov. para las hojas fósiles. Este hallazgo refuerza los ya extensos vínculos biogeográficos entre el Eoceno de Patagonia y Asia continental, proporciona el primer registro fósil relacionado con Dobinea y representa una rara presencia macrofósil gondwánica de Anacardiaceae, una familia que estaba muy extendida y diversificada en el hemisferio norte en ese momento. La diversa arquitectura foliar de las Anacardiaceae incluye varios patrones comúnmente asociados con otros grupos de plantas por lo que muchos fósiles de hojas de esta familia pueden permanecer aun mal identificados. [ABSTRACT FROM AUTHOR]

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 CO2 to 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 CO2 drawdown 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 FROM AUTHOR]

Premise: The spurge family Euphorbiaceae is prominent in tropical rainforests worldwide, particularly in Asia. There is little consensus on the biogeographic origins of the family or its principal lineages. No confirmed spurge macrofossils have come from Gondwana. Methods: We describe the first Gondwanan macrofossils of Euphorbiaceae, represented by two infructescences and associated peltate leaves from the early Eocene (52 Myr ago [Ma]) Laguna del Hunco site in Chubut, Argentina. Results: The infructescences are panicles bearing tiny, pedicellate, spineless capsular fruits with two locules, two axile lenticular seeds, and two unbranched, plumose stigmas. The fossils' character combination only occurs today in some species of the Macaranga‐Mallotus clade (MMC; Euphorbiaceae), a widespread Old‐World understory group often thought to have tropical Asian origins. The associated leaves are consistent with extant Macaranga. Conclusions: The new fossils are the oldest known for the MMC, demonstrating its Gondwanan history and marking its divergence by at least 52 Ma. This discovery makes an Asian origin of the MMC unlikely because immense oceanic distances separated Asia and South America 52 Ma. The only other MMC reproductive fossils so far known are also from the southern hemisphere (early Miocene, southern New Zealand), far from the Asian tropics. The MMC, along with many other Gondwanan survivors, most likely entered Asia during the Neogene Sahul‐Sunda collision. Our discovery adds to a substantial series of well‐dated, well‐preserved fossils from one undersampled region, Patagonia, that have changed our understanding of plant biogeographic history. [ABSTRACT FROM AUTHOR]

Agathis (Araucariaceae) is a genus of broadleaved conifers that today inhabits lowland to upper montane rainforests of Australasia and Southeast Asia. A previous report showed that the earliest known fossils of the genus, from the early Paleogene and possibly latest Cretaceous of Patagonian Argentina, host diverse assemblages of insect and fungal associations, including distinctive leaf mines. Here, we provide complete documentation of the fossilized Agathis herbivore communities from Cretaceous to Recent, describing and comparing insect and fungal damage on Agathis across four latest Cretaceous to early Paleogene time slices in Patagonia with that on 15 extant species. Notable fossil associations include various types of external foliage feeding, leaf mines, galls, and a rust fungus. In addition, enigmatic structures, possibly armored scale insect (Diaspididae) covers or galls, occur on Agathis over a 16-million-year period in the early Paleogene. The extant Agathis species, throughout the range of the genus, are associated with a diverse array of mostly undescribed damage similar to the fossils, demonstrating the importance of Agathis as a host of diverse insect herbivores and pathogens and their little-known evolutionary history. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Premise: Angiosperm leaves present a classic identification problem due to their morphological complexity. Computer‐vision algorithms can identify diagnostic regions in images, and heat map outputs illustrate those regions for identification, providing novel insights through visual feedback. We investigate the potential of analyzing leaf heat maps to reveal novel, human‐friendly botanical information with applications for extant‐ and fossil‐leaf identification. Methods: We developed a manual scoring system for hotspot locations on published computer‐vision heat maps of cleared leaves that showed diagnostic regions for family identification. Heat maps of 3114 cleared leaves of 930 genera in 14 angiosperm families were analyzed. The top‐5 and top‐1 hotspot regions of highest diagnostic value were scored for 21 leaf locations. The resulting data were viewed using box plots and analyzed using cluster and principal component analyses. We manually identified similar features in fossil leaves to informally demonstrate potential fossil applications. Results: The method successfully mapped machine strategy using standard botanical language, and distinctive patterns emerged for each family. Hotspots were concentrated on secondary veins (Salicaceae, Myrtaceae, Anacardiaceae), tooth apices (Betulaceae, Rosaceae), and on the little‐studied margins of untoothed leaves (Rubiaceae, Annonaceae, Ericaceae). Similar features drove the results from multivariate analyses. The results echo many traditional observations, while also showing that most diagnostic leaf features remain undescribed. Conclusions: Machine‐derived heat maps that initially appear to be dominated by noise can be translated into human‐interpretable knowledge, highlighting paths forward for botanists and paleobotanists to discover new diagnostic botanical characters. [ABSTRACT FROM AUTHOR]

Summary: Biodiversity today has the unusual property that 85% of plant and animal species live on land rather than in the sea, and half of these live in tropical rainforests. An explosive boost to terrestrial diversity occurred from c. 100–50 million years ago, the Late Cretaceous and early Palaeogene. During this interval, the Earth‐life system on land was reset, and the biosphere expanded to a new level of productivity, enhancing the capacity and species diversity of terrestrial environments. This boost in terrestrial biodiversity coincided with innovations in flowering plant biology and evolutionary ecology, including their flowers and efficiencies in reproduction; coevolution with animals, especially pollinators and herbivores; photosynthetic capacities; adaptability; and ability to modify habitats. The rise of angiosperms triggered a macroecological revolution on land and drove modern biodiversity in a secular, prolonged shift to new, high levels, a series of processes we name here the Angiosperm Terrestrial Revolution. [ABSTRACT FROM AUTHOR]

Leaves are the most abundant and visible plant organ, both in the modern world and the fossil record. Identifying foliage to the correct plant family based on leaf architecture is a fundamental botanical skill that is also critical for isolated fossil leaves, which often, especially in the Cenozoic, represent extinct genera and species from extant families. Resources focused on leaf identification are remarkably scarce; however, the situation has improved due to the recent proliferation of digitized herbarium material, liveplant identification applications, and online collections of cleared and fossil leaf images. Nevertheless, the need remains for a specialized image dataset for comparative leaf architecture. We address this gap by assembling an open-access database of 30,252 images of vouchered leaf specimens vetted to family level, primarily of angiosperms, including 26,176 images of cleared and x-rayed leaves representing 354 families and 4,076 of fossil leaves from 48 families. The images maintain original resolution, have user-friendly filenames, and are vetted using APG and modern paleobotanical standards. The cleared and x-rayed leaves include the Jack A. Wolfe and Leo J. Hickey contributions to the National Cleared Leaf Collection and a collection of high-resolution scanned x-ray negatives, housed in the Division of Paleobotany, Department of Paleobiology, Smithsonian National Museum of Natural History, Washington D.C.; and the Daniel I. Axelrod Cleared Leaf Collection, housed at the University of California Museum of Paleontology, Berkeley. The fossil images include a sampling of Late Cretaceous to Eocene paleobotanical sites from the Western Hemisphere held at numerous institutions, especially from Florissant Fossil Beds National Monument (late Eocene, Colorado), as well as several other localities from the Late Cretaceous to Eocene of the Western USA and the early Paleogene of Colombia and southern Argentina. The dataset facilitates new research and education opportunities in paleobotany, comparative leaf architecture, systematics, and machine learning. [ABSTRACT FROM AUTHOR]

We discuss a recent assessment by Dörken et al. (2021) regarding the affinities of the Eocene fossil species Huncocladus laubenfelsii from Laguna del Hunco (Patagonia, Argentina). We originally (Andruchow-Colombo et al. , 2019) assigned this species to the conifer family Podocarpaceae as the first certain South American macrofossil record of the phyllocladoid lineage (Huncocladus + Phyllocladus), based on a combination of numerous macro- and micromorphological vegetative characters. However, Dörken et al. (2021) rejected the podocarpaceous affinity of H. laubenfelsii and considered it to be more closely related to the cycad genera Bowenia or Eobowenia. Their assessment was based almost entirely on two cuticular characters, with only superficial consideration of the abundant additional evidence available that included several diagnostic macromorphological features. We review the two characters mentioned by these authors, and other features, and find that their suggestion is contradicted by the available evidence, maintaining our original assignment. Critical characters include presence/absence of a midvein, secondary venation pattern, arrangement and general morphology of the photosynthetic structures, and morphology and disposition of epidermal cells. [ABSTRACT FROM AUTHOR]

Premise: Solanaceae 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. Methods: The fruit morphology and calyx venation pattern of the new fossil were compared with P. infinemundi and extant species of Solanaceae. Results: Physalis hunickenii sp. nov. is clearly distinct from P. infinemundi in 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, like P. infinemundi, within the tribe Physalideae of Solanaceae. Conclusions: Both 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. [ABSTRACT FROM AUTHOR]

During the early Eocene, Patagonia had highly diverse floras that are primarily known from compression and pollen fossils. Fossil wood studies from this epoch are scarce in the region and largely absent from the Laguna del Hunco flora, which has a highly diverse and excellently preserved compression assemblage. A collection of 26 conifer woods from the Laguna del Hunco fossil-lake beds (early Eocene, ca. 52 Ma) from central-western Patagonia was studied, of which 12 could be identified to genus. The dominant species is Phyllocladoxylon antarcticum, which has affinity with early-diverging Podocarpaceae such as Phyllocladus and Prumnnopitys. A single specimen of Protophyllocladoxylon francisiae probably represents an extinct group of Podocarpaceae. In addition, two taxonomic units of cf. Cupressinoxylon with putative affinity to Podocarpaceae were found. Diverse Podocarpaceae taxa consistent with the affinities of these woods were previously reported from vegetative and reproductive macrofossils as well as pollen grains from the same source unit. Some of the woods have galleries filled with frass. Distinct growth ring boundaries indicate seasonality, inferred to represent seasonal light availability. Growth ring widths suggest that the woods came from mature trees, whereas the widths and types of some rings denote near-uniform temperature and water availability conditions. [ABSTRACT FROM AUTHOR]

Premise: Eocene floras of Patagonia document biotic response to the final separation of Gondwana. The conifer genus Araucaria, distributed worldwide during the Mesozoic, has a disjunct extant distribution between South America and Australasia. Fossils assigned to Australasian Araucaria Sect. Eutacta usually are represented by isolated organs, making diagnosis difficult. Araucaria pichileufensis E.W. Berry, from the middle Eocene Río Pichileufú (RP) site in Argentine Patagonia, was originally placed in Sect. Eutacta and later reported from the early Eocene Laguna del Hunco (LH) locality. However, the relationship of A. pichileufensis to Sect. Eutacta and the conspecificity of the Araucaria material among these Patagonian floras have not been tested using modern methods. Methods: We review the type material of A. pichileufensis alongside large (n = 192) new fossil collections of Araucaria from LH and RP, including multi‐organ preservation of leafy branches, ovuliferous complexes, and pollen cones. We use a total evidence phylogenetic analysis to analyze relationships of the fossils to Sect. Eutacta. Results: We describe Araucaria huncoensis sp. nov. from LH and improve the whole‐plant concept for Araucaria pichileufensis from RP. The two species respectively resolve in the crown and stem of Sect. Eutacta. Conclusions: Our results confirm the presence and indicate the survival of Sect. Eutacta in South America during early Antarctic separation. The exceptionally complete fossils significantly predate several molecular age estimates for crown Eutacta. The differentiation of two Araucaria species demonstrates conifer turnover during climate change and initial South American isolation from the early to middle Eocene. [ABSTRACT FROM AUTHOR]

Huncocladus laubenfelsii gen. et sp. nov. is described from the early Eocene (52 million years old) Laguna del Hunco site in Patagonia, Argentina, on the basis of a compression fossil with cuticle remains. The taxon has several similarities with Phyllocladus , together with characters that are absent in extant Phyllocladus species but are otherwise typical of the enclosing scale-leaved clade. Consequently, Huncocladus is interpreted as a relative of Phyllocladus , possibly belonging to its stem group. This view is supported by a phylogenetic analysis of Podocarpaceae, which recovers Huncocladus as sister to Phyllocladus within the here-termed phyllocladoid clade (Phyllocladus + Huncocladus). Huncocladus laubenfelsii is the first macrofossil record of the phyllocladoid lineage in South America or anywhere in the western hemisphere, vastly extending its historical range and constituting an additional lineage shared between Eocene Patagonia and extant and extinct Australasian and South-east Asian rainforests. The disappearance of phyllocladoids from South America adds to the general extinction pattern described previously for southern hemisphere Podocarpaceae, associated with the family's low drought tolerance in the face of climate change (i.e. aridification). Huncocladus is the oldest record of the phyllocladoids, and it represents a new reference point for temporal calibration and biogeographic inference for the evolution of conifers and Australasian rainforests. [ABSTRACT FROM AUTHOR]

Denk et al. agree that we reported the first fossil Fagaceae from the Southern Hemisphere. We appreciate their general enthusiasm for our findings, but we reject their critiques, which we find misleading and biased. The new fossils unequivocally belong to Castanopsis, and substantial evidence supports our Southern Route to Asia hypothesis. [ABSTRACT FROM AUTHOR]

Premise of research. Cyclocarya Iljinskaya (Juglandaceae) is a genus with a single living species that is endemic to central and south China. The genus has an abundant North American and Eurasian fossil record from the Paleocene to the Pliocene, documenting its spread across Europe to western Siberia during the Oligocene and its arrival in Japan by the Miocene. However, there have been no fossil occurrences of Cyclocarya near its modern distribution. In this study, we describe a new species of Cyclocarya from the upper Miocene Nanlin Formation in Lianghe County, western Yunnan Province, southwest China, and discuss its biogeographic implications. Methodology. We examined the fossil fruit usingLMand SEM, and we compared its morphology with fruits of fossil Cyclocarya and extant Cyclocarya paliurus (Batalin) Iljinsk. Pivotal results. The fossil fruit of Cyclocarya simipaliurus sp. nov. consists of a small nutlet that is surrounded by a circular and flange-likewing. The nutlet is circular in plan viewand oblate in longitudinal view. Nutlet structure and the epidermal characteristics of the wing indicate that this fossil fruit is almost identical to that of the extant species, C. paliurus. Conclusions. The specimen reported here is the only reliable fossil of Cyclocarya known from China. The new fossil species helps to fill a significant gap in the fossil record of Cyclocarya, indicating that the genus had reached the westernmost boundary of its modern distribution by the late Miocene. Western Yunnan had a warm and humid climate during the late Neogene, and the rapid uplift of the Yunnan Plateau began in the Pliocene. Pleistocene glaciations may have forced Cyclocarya to retreat from western Yunnan, and the uplifted mountains and deep river valleys might have posed barriers for reconnection during the interglacials. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: The flip-leaved podocarp Retrophyllum has a disjunct extant distribution in South American and Australasian tropical rainforests and a Gondwanic fossil record since the Eocene. Evolutionary, biogeographic, and paleoecological insights from previously described fossils are limited because they preserve little foliar variation and no reproductive structures. METHODS: We investigated new Retrophyllum material from the terminal Cretaceous Lefipán, the early Eocene Laguna del Hunco, and the early/middle Eocene Río Pichileufú floras of Patagonian Argentina. We also reviewed type material of historical Eocene fossils from southern Chile. KEY RESULTS: Cretaceous Retrophyllum superstes sp. nov. is described from a leafy twig, while Eocene R. spiralifolium sp. nov. includes several foliage forms and a peduncle with 13 pollen cones. Both species preserve extensive damage from sap-feeding insects associated with foliar transfusion tissue. The Eocene species exhibits a suite of characters linking it to both Neotropical and West Pacific Retrophyllum, along with several novel features. Retrophyllum araucoensis (Berry) comb. nov. stabilizes the nomenclature for the Chilean fossils. CONCLUSIONS: Retrophyllum is considerably older than previously thought and is a survivor of the end-Cretaceous extinction. Much of the characteristic foliar variation and pollen-cone morphology of the genus evolved by the early Eocene. The mixed biogeographic signal of R. spiralifolium supports vicariance and represents a rare Neotropical connection for terminal-Gondwanan Patagonia, which is predominantly linked to extant Australasian floras due to South American extinctions. The leaf morphology of the fossils suggests significant drought vulnerability as in living Retrophyllum, indicating humid paleoenvironments. [ABSTRACT FROM AUTHOR]

The nightshade family Solanaceae holds exceptional economic and cultural importance. The early diversification of Solanaceae is thought to have occurred in South America during its separation from Gondwana, but the family’s sparse fossil record provides few insights. We report 52.2-million-year-old lantern fruits from terminal-Gondwanan Patagonia, featuring highly inflated, five-lobed calyces, as a newly identified species of the derived, diverse New World genus Physalis (e.g., groundcherries and tomatillos). The fossils are considerably older than corresponding molecular divergence dates and demonstrate an ancient history for the inflated calyx syndrome. The derived position of these early Eocene fossils shows that Solanaceae were well diversified long before final Gondwanan breakup. [ABSTRACT FROM AUTHOR]

The cycads pose classic problems in evolutionary biogeography, owing to their far-flung extant distributions and the sparse fossil records of living genera. A noteworthy example is Tribe Encephalarteae of Family Zamiaceae, today consisting of Encephalartos (Africa) and the Australian genera Lepidozamia and Macrozamia. Numerous petrified trunks of Encephalarteae described from the Cretaceous of Patagonia, Antarctica, and India indicate far larger past distributions across Gondwana and subsequent extinctions. The only fossils close to the current range are Paleogene leaf fragments from Australia assigned to Lepidozamia and Macrozamia. Here, we report a large frond piece and several isolated leaflets of a compressed cycad, along with an associated spiny petiole, from the late-Gondwanan, 52.2 Ma Laguna del Hunco flora of Patagonia, Argentina. Austrozamia stockeyi gen. et sp. nov., has the novel combination of an Encephalartos-type leaf and Lepidozamia-type cuticle. The Australian Lepidozamia fossils, widely used for molecular clock calibrations, could also represent an extinct genus. Austrozamia stockeyi demonstrates survival of the Encephalarteae in Patagonia and presumably across Gondwana until its terminal phase, adding a striking new component to the growing list of South American plant extinctions associated with Antarctic separation and related climate changes. [ABSTRACT FROM AUTHOR]

Understanding the extremely variable, complex shape and venation characters of angiosperm leaves is one of the most challenging problems in botany. Machine learning offers opportunities to analyze large numbers of specimens, to discover novel leaf features of angiosperm clades that may have phylogenetic significance, and to use those characters to classify unknowns. Previous computer vision approaches have primarily focused on leaf identification at the species level. It remains an open question whether learning and classification are possible among major evolutionary groups such as families and orders, which usually contain hundreds to thousands of species each and exhibit many times the foliar variation of individual species. Here, we tested whether a computer vision algorithm could use a database of 7,597 leaf images from 2,001 genera to learn features of botanical families and orders, then classify novel images. The images are of cleared leaves, specimens that are chemically bleached, then stained to reveal venation. Machine learning was used to learn a codebook of visual elements representing leaf shape and venation patterns. The resulting automated system learned to classify images into families and orders with a success rate many times greater than chance. Of direct botanical interest, the responses of diagnostic features can be visualized on leaf images as heat maps, which are likely to prompt recognition and evolutionary interpretation of a wealth of novel morphological characters. With assistance from computer vision, leaves are poised to make numerous new contributions to systematic and paleobotanical studies. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Puzzling rocks and complicated clocks: how to optimize molecular dating approaches in historical phytogeography" by Q Wang, and K.-S. Mao in a 2016 issue.

283I.283II.284III.284IV.287V.288288References288 Summary: Evolutionary divergence‐age estimates derived from molecular ‘clocks’ are frequently correlated with paleogeographic, paleoclimatic and extinction events. One prominent hypothesis based on molecular data states that the dominant pattern of Southern Hemisphere biogeography is post‐Gondwanan clade origins and subsequent dispersal across the oceans in a metaphoric ‘Green Web’. We tested this idea against well‐dated Patagonian fossils of 19 plant lineages, representing organisms that actually lived on Gondwana. Most of these occurrences are substantially older than their respective, often post‐Gondwanan molecular dates. The Green Web interpretation probably results from directional bias in molecular results. Gondwanan history remains fundamental to understanding Southern Hemisphere plant radiations, and we urge significantly greater caution when using molecular dating to interpret the biological impacts of geological events. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: The diverse early Eocene flora from Laguna del Hunco (LH) in Patagonia, Argentina has many nearest living relatives (NLRs) in Australasia but few in South America, indicating the differential survival of an ancient, trans-Antarctic rainforest biome. To better understand this significant biogeographic pattern, we used detailed comparisons of leaf size and floristics to quantify the legacy of LH across a large network of Australian rainforest-plot assemblages. METHODS: We applied vein scaling, a new method for estimating the original areas of fragmented leaves. We then compared leaf size and floristics at LH with living Australian assemblages and tabulated the climates of those where NLRs occur, along with additional data on climatic ranges of "ex-Australian" NLRs that survive outside of Australia. KEY RESULTS: Vein scaling estimated areas as accurately as leaf-size classes. Applying vein scaling to fossil fragments increased the grand mean area of LH by 450 mm², recovering more originally large leaves. The paleoflora has a majority of microphyll leaves, comparable to leaf litter in subtropical Australian forests, which also have the greatest floristic similarity to LH. Tropical Australian assemblages also share many taxa with LH, and ex-Australian NLRs mostly inhabit cool, wet montane habitats no longer present in Australia. CONCLUSIONS: Vein scaling is valuable for improving the resolution of fossil leaf-size distributions by including fragmented specimens. The legacy of LH is evident not only in subtropical and tropical Australia but also in tropical montane Australasia and Southeast Asia, reflecting the disparate histories of surviving Gondwanan lineages. [ABSTRACT FROM AUTHOR]

Premise of study: Have Gondwanan rainforest floral associations survived? Where do they occur today? Have they survived continuously in particular locations? How significant is their living floristic signal? We revisit these classic questions in light of significant recent increases in relevant paleobotanical data. • Methods: We traced the extinction and persistence of lineages and associations through the past across four now separated regions-Australia, New Zealand, Patagonia, and Antarctica-using fossil occurrence data from 63 well-dated Gondwanan rainforest sites and 396 constituent taxa. Fossil sites were allocated tofour age groups: Cretaceous, Paleocene-Eocene, Neo-gene plus Oligocene, and Pleistocene. We compared the modern and ancient distributions of lineages represented in the fossil record to see if dissimilarity increased with time. We quantified similarity-dissimilarity of composition and taxonomic structure among fossil assemblages, and between fossil and modern assemblages. • Key results: Strong similarities between ancient Patagonia and Australia confirmed shared Gondwanan rainforest history, but more of the lineages persisted in Australia. Samples of ancient Australia grouped with the extant floras of Australia, New Guinea, New Caledonia, Fiji, and Mt. Kinabalu. Decreasing similarity through time among the regional floras of Antarctica, Patagonia, New Zealand, and southern Australia reflects multiple extinction events. • Conclusions: Gondwanan rainforest lineages contribute significantly to modern rainforest community assembly and often co-occur in widely separated assemblages far from their early fossil records. Understanding how and where lineages from ancient Gondwanan assemblages co-occur today has implications for the conservation of global rainforest vegetation, including in the Old World tropics. [ABSTRACT FROM AUTHOR]

* Premise of the study: The Qinghai-Tibet Plateau is a major center of plant diversity and endemism, but little is known about how this developed due to the region's very scarce paleobotanical record. The silverberry genus Elaeagnus (Elaeagnaceae) reaches its greatest diversity (54 species) and endemism (36 species) in this area. Fossil Elaeagnaceae could provide significant evidence for the phylogeny and biogeography of the family and contribute primary data regarding the evolution of the unique Qinghai-Tibet Plateau flora in its dramatic setting of tectonic and climatic change. * Methods: We describe four fossil leaves with diagnostic features of Elaeagnus from the late Miocene of eastern Tibet, modern altitude of 3910 m a.s.l.. We also review prior fossil records of Elaeagnaceae. * Key results: The well-preserved, densely packed, stellate scales on fossil leaf surfaces are diagnostic of Elaeagnaceae. We assign these fossil leaves to Elaeagnus tibetensis T. Su et Z.K. Zhou sp. nov., comprising the first confirmed fossil Elaeagnus leaves worldwide. * Conclusions: Elaeagnus was present in eastern Tibet by the late Miocene. Together with previous fossil records, the new species supports a Holarctic history of the family. The diversification of Elaeagnus in the Qinghai-Tibet Plateau and adjacent areas might have been driven by continuous uplift at least since the late Miocene, causing formation of complex topography and climate with high rainfall seasonality. The characteristic scales on leaf surfaces are likely to be an important functional adaptation to seasonal droughts during early spring. [ABSTRACT FROM AUTHOR]

Plant and associated insect-damage diversity in the western U.S.A. decreased significantly at the Cretaceous-Paleogene (K-Pg) boundary and remained low until the late Paleocene. However, the Mexican Hat locality (ca. 65 Ma) in southeastern Montana, with a typical, low-diversity flora, uniquely exhibits high damage diversity on nearly all its host plants, when compared to all known local and regional early Paleocene sites. The same plant species show minimal damage elsewhere during the early Paleocene. We asked whether the high insect damage diversity at Mexican Hat was more likely related to the survival of Cretaceous insects from refugia or to an influx of novel Paleocene taxa. We compared damage on 1073 leaf fossils from Mexican Hat to over 9000 terminal Cretaceous leaf fossils from the Hell Creek Formation of nearby southwestern North Dakota and to over 9000 Paleocene leaf fossils from the Fort Union Formation in North Dakota, Montana, and Wyoming. We described the entire insect-feeding ichnofauna at Mexican Hat and focused our analysis on leaf mines because they are typically host-specialized and preserve a number of diagnostic morphological characters. Nine mine damage types attributable to three of the four orders of leaf-mining insects are found at Mexican Hat, six of them so far unique to the site. We found no evidence linking any of the diverse Hell Creek mines with those found at Mexican Hat, nor for the survival of any Cretaceous leaf miners over the K-Pg boundary regionally, even on well-sampled, surviving plant families. Overall, our results strongly relate the high damage diversity on the depauperate Mexican Hat flora to an influx of novel insect herbivores during the early Paleocene, possibly caused by a transient warming event and range expansion, and indicate drastic extinction rather than survivorship of Cretaceous insect taxa from refugia. [ABSTRACT FROM AUTHOR]

The fossil record demonstrates that past climate changes and extinctions significantly affected the diversity of insect leaf-feeding damage, implying that the richness of damage types reflects that of the unsampled damage makers, and that the two are correlated through time. However, this relationship has not been quantified for living leaf-chewing insects, whose richness and mouthpart convergence have obscured their value for understanding past and present herbivore diversity. We hypothesized that the correlation of leaf-chewing damage types (DTs) and damage maker richness is directly observable in living forests. Using canopy access cranes at two lowland tropical rainforest sites in Panamá to survey 24 host-plant species, we found significant correlations between the numbers of leaf chewing insect species collected and the numbers of DTs observed to be made by the same species in feeding experiments, strongly supporting our hypothesis. Damage type richness was largely driven by insect species that make multiple DTs. Also, the rank-order abundances of DTs recorded at the Panamá sites and across a set of latest Cretaceous to middle Eocene fossil floras were highly correlated, indicating remarkable consistency of feeding-mode distributions through time. Most fossil and modern host-plant pairs displayed high similarity indices for their leaf-chewing DTs, but informative differences and trends in fossil damage composition became apparent when endophytic damage was included. Our results greatly expand the potential of insect-mediated leaf damage for interpreting insect herbivore richness and compositional heterogeneity from fossil floras and, equally promisingly, in living forests. [ABSTRACT FROM AUTHOR]

The Salamanca Formation of the San Jorge Basin (Patagonia, Argentina) preserves critical records of Southern Hemisphere Paleo cene biotas, but its age remains poorly resolved, with estimates ranging from Late Cretaceous to middle Paleocene. We report a multi-disciplinary geochronologic study of the Salamanca Formation and overlying Río Chico Group in the western part of the basin . New constraints include (1) an 40Ar/39Ar age determination of 67.31 ±0.55 Ma from a basalt fl ow underlying the Salamanca Formation, (2) micropaleontological results indicating an early Danian age for the base of the Salamanca Formation, (3) laser ablation HR-MC-ICP-MS (high resolutionmulti collector-inductively coupled plasmamass spectrometry) U-Pb ages and a highresolution TIMS (thermal ionization mass spectrometry) age of 61.984 ±0.041(0.074) [0.100] Ma for zircons from volcanic ash beds in the Peñas Coloradas Formation (Río Chico Group), and (4) paleomagnetic results indicating that the Salamanca Formation in this area is entirely of normal polarity, with reversals occurring in the Río Chico Group. Placing these new age constraints in the context of a sequence stratigraphic model for the basin, we correlate the Salamanca Formation in the study area to Chrons C29n and C28n, with the Banco Negro Inferior (BNI), a mature widespread fossiliferous paleosol unit at the top of the Salamanca Formation, corresponding to the top of Chron C28n. The diverse paleo botanical assemblages from this area are here assigned to C28n (64.67- 63.49 Ma), 2-3 million years older than previously thought, adding to growing evidence for rapid Southern Hemisphere fl oral recovery after the Cretaceous-Paleogene extinction. Important Peligran and "Carodnia" zone vertebrate fossil assemblages from coastal BNI and Peñas Coloradas exposures are likely older than previously thought and correlate to the early Torrejonian and early Tiffanian North American Land Mammal Ages, respectively. [ABSTRACT FROM AUTHOR]

* Premise of the study: Agathis is an iconic genus of large, ecologically important, and economically valuable conifers that range over lowland to upper montane rainforests from New Zealand to Sumatra. Exploitation of its timber and copal has greatly reduced the genus's numbers. The early fossil record of Agathis comes entirely from Australia, often presumed to be its area of origin. Agathis has no previous record from South America. * Methods: We describe abundant macrofossils of Agathis vegetative and reproductive organs, from early and middle Eocene rainforest paleofloras of Patagonia, Argentina. The leaves were formerly assigned to the New World cycad genus Zamia. * Key results: Agathis zamunerae sp. nov. is the first South American occurrence and the most complete representation of Agathis in the fossil record. Its morphological features are fully consistent with the living genus. The most similar living species is A. lenticula, endemic to lower montane rainforests of northern Borneo. * Conclusions: Agathis zamunerae sp. nov. demonstrates the presence of modern-aspect Agathis by 52.2 mya and vastly in creases the early range and possible areas of origin of the genus. The revision from Zamia breaks another link between the Eocene and living floras of South America. Agathis was a dominant, keystone element of the Patagonian Eocene floras, along side numerous other plant taxa that still associate with it in Australasia and Southeast Asia. Agathis extinction in South America was an integral part of the transformation of Patagonian biomes over millions of years, but the living species are disappearing from their ranges at a far greater rate. [ABSTRACT FROM AUTHOR]

Widespread deforestation, agriculture, and construction of milldams by European settlers greatly influenced valley-bottom stream morphology and riparian vegetation in the northeastern USA. The former broad, tussock-sedge wetlands with small, anastomosing channels were converted into today’s incised, meandering streams with unstable banks that support mostly weedy, invasive vegetation. Vast accumulations of fine-grained “legacy” sediments that blanket the regional valley-bottom Piedmont landscape now are being reworked from stream banks, significantly impairing the ecological health of downstream water bodies, most notably the Chesapeake Bay. However, potential restoration is impaired by lack of direct knowledge of the pre-settlement riparian and upslope floral ecosystems. We studied the subfossil leaf flora of Denlingers Mill, an obsolete (breached) milldam site in southeastern Pennsylvania that exhibits a modern secondary forest growing atop thin soils, above bedrock outcrops immediately adjacent to a modified, incised stream channel. Presumably, an overhanging old-growth forest also existed on this substrate until the early 1700s and was responsible for depositing exceptionally preserved, minimally transported subfossil leaves into hydric soil strata, which immediately underlie post-European settlement legacy sediments. We interpret the eleven identified species of the subfossil assemblage to primarily represent a previously unknown, upland Red Oak-American Beech mixed hardwood forest. Some elements also appear to belong to a valley-margin Red Maple-Black Ash swamp forest, consistent with preliminary data from a nearby site. Thus, our results add significantly to a more complete understanding of the pre-European settlement landscape, especially of the hardwood tree flora. Compared with the modern forest, it is apparent that both lowland and upslope forests in the region have been modified significantly by historical activities. Our study underscores that generally overlooked subfossil leaves can provide important, local, temporally constrained paleoecological data, with much potential value in this case for stream and wetland restoration decisions in the mid-Atlantic region. [ABSTRACT FROM AUTHOR]

* Premise of the Study: The early Eocene Laguna del Hunco caldera-lake paleoflora (ca. 52 Ma) from Chubut Province, Argentina, is notably diverse and includes many conifer and angiosperm lineages that are extinct in South America but extant in Australasian rainforests. No ferns have been previously described from Laguna del Hunco. We describe and interpret a new species of fossil Osmundaceae based on fertile and sterile pinnae. * Methods: The fossil specimens were compared with other extant and fossil Osmundaceae based on living and herbarium mate rial and published descriptions. A morphological matrix based on 29 characters was constructed for 17 living species in Osmundaceae, four species assigned to the fossil genus Todites, and the new fossil species. Phylogenetic analyses were conducted under parsimony using morphology and total evidence matrices. * Key Results: Both the new fossil and the Todites species were consistently resolved within the leptopteroid clade of Osmundaceae, and the new species resolved in a clade with the two living Todea species, which are now restricted to Australia, New Guinea, New Zealand, and southern Africa. * Conclusions: Todea amissa sp. nov. is the first record of Todea, living or fossil, in South America and only the second fossil record worldwide. The distribution of extant Todea on Gondwanan continents other than South America is broadly shared with other taxa from Laguna del Hunco, further indicating that a large component of this flora represents a Gondwanic biome that is no longer found on the South American continent. [ABSTRACT FROM AUTHOR]

The idea that South America was an island continent over most of the Cenozoic, during which its unusual mammalian faunas evolved in isolation, is outstandingly influential in biogeography. Although large numbers of recent fossil discoveries and related advances require that the original isolation concept be significantly modified, it is still repeated in much current literature. The persistence of the idea inspired us to present here an integrated paleobiogeographic account of mammals, reptiles, and plants from the Jurassic to the Paleogene of Patagonia, which has by far the richest fossil record on the continent. All three groups show distribution patterns that are broadly consistent with South America's long separation history, first from Laurasia by the Late Jurassic, then from Africa and India-Madagascar during the late Early Cretaceous, and finally from Antarctica and Australia during the early-middle Eocene, after which "isolation" finally commenced. We highlight areas of promising future research and provide an updated view of South American isolation. [ABSTRACT FROM AUTHOR]

Premise: Digital image libraries are an integral part of specimen‐based research. However, coding and extracting metadata for hundreds of specimens on a personal computer can be complex. In addition, most existing workflows require downsampling or platform switching and do not link character data directly to the images. Methods and Results: We demonstrate a method to code and embed into images the standard leaf architecture and insect‐damage characters that are widely used in paleobotany. Using the visual file browser Adobe Bridge, customizable and searchable keywords can be applied directly and reversibly to individual full‐resolution images, and the data can be extracted and formatted into a matrix using scripts. Conclusions: Our approach is intuitive and acts as a digital mimic and complement to the experience of sorting and analyzing specimens in‐person. Keywords can be easily customized for other data types that require visual sorting using image libraries. [ABSTRACT FROM AUTHOR]

* Premise of the study: Eocene caldera-lake beds at Laguna del Hunco (LH, ca. 52.2 Ma) and R í o Pichileufú (RP, ca. 47.7 Ma) in Argentine Patagonia provide copious information about the biological history of Gondwana. Several plant genera from these sites are known as fossils from southern Australia and New Zealand and survive only in Australasian rainforests. The potential presence of Dacrycarpus (Podocarpaceae) holds considerable interest due to its extensive foliage-fossil record in Gondwana, its remarkably broad modern distribution in Southeast Asian and Australasian rainforests, its high physiological moisture requirements, and its bird-dispersed seeds. However, the unique seed cones that firmly diagnose Dacrycarpus were not previously known from the fossil record. * Methods: I describe and interpret fertile (LH) and vegetative (LH and RP) material of Dacrycarpus and present a nomenclatural revision for fossil Dacrycarpus from South America. * Key results: Dacrycarpus puertae sp. nov. is the first fossil occurrence of the unusual seed cones that typify living Dacrycarpus, attached to characteristic foliage, and of attached Dacrycarpus pollen cones and foliage. Dacrycarpus puertae is indistinguishable from living D. imbricatus (montane, Burma to Fiji). Dacrycarpus chilensis (Engelhardt) comb. nov. is proposed for Eocene vegetative material from Chile. * Conclusions: Modern-aspect Dacrycarpus was present in Eocene Patagonia, demonstrating an astonishingly wide-ranging paleogeographic history and implying a long evolutionary association with bird dispersers. Dacrycarpus puertae provides the first significant Asian link for Eocene Patagonian floras, strengthens the biogeographic connections from Patagonia to Australasia across Antarctica during the warm Eocene, and indicates high-rainfall paleoenvironments. [ABSTRACT FROM AUTHOR]

The 51.9 Ma Laguna del Hunco (LH) and 47.5 Ma Río Pichileufd (RP) floras from Patagonia, Argentina are unusually rich, angiosperm-dominated assemblages with living relatives in the low-latitude West Pacific, neotropics, and temperate southern latitudes. The diverse gymnosperms in these floras are important for Gondwanan biogeographic history and paleoclimatic interpretations. "Libocedrus" prechilensis Berry 1938 (Cupressaceae), previously known only from the holotype (RP), a vegetative branch, is revised here based on new material from both localities, including a seed cone attached to a shoot with cuticle (LH). Characters of these fossils are diagnostic of monotypic Papuacedrus (highlands of New Guinea and Moluccas). Living P. papuana is most abundant in cloud forests receiving up to 4 m rainfall annually, whereas Austrocedrus (Libocedrus) chilensis, the basis of comparison when the fossil species was named, inhabits dry, cold steppe margins to mediterranean climates in southern South America. We establish Papuacedrus prechilensis comb. nov., which simultaneously invalidates a southern South American connection for the fossil floras and reveals a link to West Pacific montane rainforests. Combined evidence indicates a biome similar to extant subtropical, or tropical montane, rainforests that persisted for at least 4.4 Myr, linking elevated floral richness to abundant rainfall. [ABSTRACT FROM AUTHOR]

The Paleocene-Eocene Thermal Maximum (PETM, 55.8 Ma), an abrupt global warming event linked to a transient increase in pCO2, was comparable in rate and magnitude to modern anthropogenic climate change. Here we use plant fossils from the Bighorn Basin of Wyoming to document the combined effects of temperature and pCO2 on insect herbivory. We examined 5,062 fossil leaves from five sites positioned before, during, and after the PETM (59-55.2 Ma). The amount and diversity of insect damage on angiosperm leaves, as well as the relative abundance of specialized damage, correlate with rising and falling temperature. All reach distinct maxima during the PETM, and every PETM plant species is extensively damaged and colonized by specialized herbivores. Our study suggests that increased insect herbivory is likely to be a net long-term effect of anthropogenic pCO2 increase and warming temperatures. [ABSTRACT FROM AUTHOR]

Few South American macrofloras of Paleocene age are known, and this limits our knowledge of diversity and composition between the end-Cretaceous event and the Eocene appearance of high floral diversity. We report new, unbiased collections of 2516 compression specimens from the Paleocene Salamanca Formation (ca. 61.7 Ma) from two localities in the Palacio de los Loros exposures in southern Chubut, Patagonia, Argentina. Our samples reveal considerably greater richness than was previously known from the Paleocene of Patagonia, including 36 species of angiosperm leaves as well as angiosperm fruits, flowers, and seeds; ferns; and conifer leaves, cones, and seeds. The floras, which are from siltstone and sandstone channel-fills deposited on low-relief floodplain landscapes in a humid, warm temperate climate, are climatically and paleoenvironmentally comparable to many quantitatively collected Paleocene floras from the Western Interior of North America. Adjusted for sample size, there are >50% more species at each Palacio de los Loros quarry than in any comparable U.S. Paleocene sample. These results indicate more vibrant terrestrial ecosystems in Patagonian than in North American floodplain environments ∼4 m.y. after the end-Cretaceous extinction, and they push back the time line 10 m.y. for the evolution of high fl oral diversity in South America. The cause of the disparity is unknown but could involve reduced impact effects because of greater distance from the Chicxulub site, higher latest Cretaceous diversity, or faster recovery or immigration rates. [ABSTRACT FROM AUTHOR]

Food web recovery from mass extinction is poorly understood. We analyzed insect-feeding damage on 14,999 angiosperm leaves from 14 latest Cretaceous, Paleocene, and early Eocene sites in the western interior United States. Most Paleocene floras have low richness of plants and of insect damage. However, a low-diversity 64.4-million-year-old flora from southeastern Montana shows extremely high insect damage richness, especially of leaf mining, whereas an anomalously diverse 63.8-million-year-old flora from the Denver Basin shows little damage and virtually no specialized feeding. These findings reveal severely unbalanced food webs 1 to 2 million years after the end-Cretaceous extinction 65.5 million years ago. [ABSTRACT FROM AUTHOR]

Leaf teeth are conspicuous and often diagnostic features of many plant species. In mesic environments with sufficient nutrient resources, the percentage of toothed species in extant floras generally correlates negatively with temperature; consequently, fossil leaf teeth are widely used to estimate continental paleotemperatures. However, the function of leaf teeth with respect to climate is poorly understood. Here, we test the hypothesis that teeth enhance rates of carbon uptake at the beginning of the growing season when temperatures are limiting. We measure the seasonal patterns of leaf-margin photosynthesis and transpiration for 60 woody species from two temperate regions with differing climates (Pennsylvania and North Carolina). Three significant results are, first, physiological activity at leaf margins is greatest early in the growing season (first 30 d); second, toothed margins are more active with respect to photosynthesis and transpiration than untoothed margins; finally, leaf margins are more active in species native to colder Pennsylvania. The toothed species increase transpiration and photosynthate production early in the growing season relative to untoothed species and do so more in the Pennsylvania sample, maximizing carbon gain when temperature is limiting but moisture and nutrient availability are not. This mechanism may provide a proportionally increasing selective advantage to toothed species with decreasing temperature that is reflected in empirical correlations used for paleotemperature estimation. [ABSTRACT FROM AUTHOR]

The sizes and shapes (physiognomy) of fossil leaves are widely applied as proxies for paleoclimatic and paleoecological variables. However, significant improvements to leaf-margin analysis, used for nearly a century to reconstruct mean annual temperature (MAT), have been elusive; also, relationships between physiognomy and many leaf ecological variables have not been quantified. Using the recently developed technique of digital leaf physiognomy, correlations of leaf physiognomy to MAT, leaf mass per area, and nitrogen content are quantified for a set of test sites from North and Central America. Many physiognomic variables correlate significantly with MAT, indicating a coordinated, convergent evolutionary response of fewer teeth, smaller tooth area, and lower degree of blade dissection in warmer environments. In addition, tooth area correlates negatively with leaf mass per area and positively with nitrogen content. Multiple linear regressions based on a subset of variables produce more accurate MAT estimates than leaf-margin analysis (standard errors of ±2 vs. ±3°C); improvements are greatest at sites with shallow water tables that are analogous to many fossil sites. The multivariate regressions remain robust even when based on one leaf per species, and the model most applicable to fossils shows no more signal degradation from leaf fragmentation than leaf-margin analysis. [ABSTRACT FROM AUTHOR]

South America has some of the most diverse floras and insect faunas that are known, but its Cenozoic fossil record of insects and insect herbivory is sparse. We quantified insect feeding on 3,599 leaves from the speciose Laguna del Hunco flora (Chubut, Argentina), which dates to the early Eocene climatic optimum (52 million years ago) and compared the results with three well preserved, rich, and identically analyzed early- and middle-Eocene floras from the following sites in North America: Republic, WA; Green River, UT; and Sourdough, WV. We found significantly more damage diversity at Laguna del Hunco than in the North American floras, whether measured on bulk collections or on individual plant species, for both damage morphotypes and feeding groups. An ancient history of rich, specialized plant-insect associations on diverse plant lineages in warm climates may be a major factor contributing to the current biodiversity of South America. [ABSTRACT FROM AUTHOR]

The origins of South America's exceptional plant diversity are poorly known from the fossil record. We report on unbiased quantitative collections of fossil floras from Laguna del Hunco (LH) and RIo Pichileufú (RP) in Patagonia, Argentina. These sites represent a frost-free humid biome in South American middle latitudes of the globally warm Eocene. At LH, from 4,303 identified specimens, we recognize 186 species of plant organs and 152 species of leaves. Adjusted for sample size, the LH flora is more diverse than comparable Eocene floras known from other continents. The RP flora shares several taxa with LH and appears to be as rich, although sampling is preliminary. The two floras were previously considered coeval. However, 40Ar/39Ar dating of three ash-fall tuff beds in close strati- graphic association with the RP flora indicates an age of 47A6 ± 0.05 Ma, 4.5 million years younger than LH, for which one tuff is reanalyzed here as 51.91 ± 0.22 Ma. Thus, diverse floral associations in Patagonia evolved by the Eocene, possibly in response to global warming, and were persistent and areally extensive. This suggests extraordinary richness at low latitudes via the latitudinal diversity gradient, corroborated by published palynological data from the Eocene of Colombia. [ABSTRACT FROM AUTHOR]

Tropical South America has the highest plant diversity of any region today, but this richness is usually characterized as a geologically recent development (Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco in Patagonia, Argentina, paleolatitude ∼47°S, we report 102 leaf species. Radioisotopic and paleomagnetic analyses indicate that the flora was deposited 52 million years ago, the time of the early Eocene climatic optimum, when tropical plant taxa and warm, equable climates reached middle latitudes of both hemispheres. Adjusted for sample size, observed richness exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America. [ABSTRACT FROM AUTHOR]

Terrestrial climates near the time of the end-Cretaceous mass extinction are poorly known, limiting understanding of environmentally driven changes in biodiversity that occurred before bolide impact. We estimate paleotemperatures for the last ≈1.1 million years of the Cretaceous (≈66.6-65.5 million years ago, Ma) by using fossil plants from North Dakota and employ paleomagnetic stratigraphy to correlate the results to foraminiferal paleoclimatic data from four middle- and high-latitude sites. Both plants and foraminifera indicate warming near 66.0 Ma, a warming peak from ≈65.8 to 65.6 Ma, and cooling near 65.6 Ma, suggesting that these were global climate shifts. The warming peak coincides with the immigration of a thermophilic flora, maximum plant diversity, and the poleward range expansion of thermophilic foraminifera. Plant data indicate the continuation of relatively cool temperatures across the Cretaceous -- Paleogene boundary; there is no indication of a maior warming immediately after the boundary as previously reported. Our temperature proxies correspond well with recent pCO[SUB2] data from paleosol carbonate, suggesting a coupling of pCO[SUB2] and temperature. To the extent that biodiversity is correlated with temperature, estimates of the severity of end-Cretaceous extinctions that are based on occurrence data from the warming peak are probably inflated, as we illustrate for North Dakota plants. However, our analysis of climate and facies considerations shows that the effects of bolide impact should be regarded as the most significant contributor to these plant extinctions. [ABSTRACT FROM AUTHOR]

Reports that climate change and plant defense had linked effects on insect herbivory over an extended period and within a single region. Effect of climate change on herbivorous insects; Study time periods used; Extant plant-insect associations.

Presents a study which examined the timing radiations of leaf beetles. Factors which account for the diversity of leaf beetles; Importance of the diagnostic insect damage on fossil angiosperms; Associations between insects and monocots.

Focuses on a paleobotanical analysis of the late Paleocene-early Eocene climate changes in southern Wyoming. Paleobotanical investigation of the Green River Basin; Species of plant macrofossils obtained by intensive sampling; Leaf morphologies and taxonomic affinities of the macrofossils.

Presents a research report on the response of plant-insect associations to Paleocene-Eocene warming. Diversity of modern herbivorous insects and their pressure on plant hosts increasing with decreasing latitude; Study of insect damage on fossil plants; Comparison of two floral samples from the Great Divide, Green River and Washakie basins of Southwestern Wyoming; Demonstration that the effects of global warming on plant-insect interactions are detectable in the fossil record.

Presents a study to estimate paleoprecipitation utilizing fossil leaves as indicators. Details on study conducted; Discussion on leaf area analysis and precipitation; Proposed example of `early' middle Eocene of the United States Western Interior; Indication of study.

Many plant genera in the tropical West Pacific are survivors from the paleo-rainforests of Gondwana. For example, the oldest fossils of the Malesian and Australasian conifer Agathis (Araucariaceae) come from the early Paleocene and possibly latest Cretaceous of Patagonia, Argentina (West Gondwana). However, it is unknown whether dependent ecological guilds or lineages of associated insects and fungi persisted on Gondwanan host plants like Agathis through time and space. We report insect-feeding and fungal damage on Patagonian Agathis fossils from four latest Cretaceous to middle Eocene floras spanning ca. 18 Myr and compare it with damage on extant Agathis. Very similar damage was found on fossil and modern Agathis, including blotch mines representing the first known Cretaceous–Paleogene boundary crossing leaf-mine association, external foliage feeding, galls, possible armored scale insect (Diaspididae) covers, and a rust fungus (Pucciniales). The similar suite of damage, unique to fossil and extant Agathis, suggests persistence of ecological guilds and possibly the component communities associated with Agathis since the late Mesozoic, implying host tracking of the genus across major plate movements that led to survival at great distances. The living associations, mostly made by still-unknown culprits, point to previously unrecognized biodiversity and evolutionary history in threatened rainforest ecosystems. Michael Donovan et al. examine well-preserved remains of diverse insect-feeding and fungal damage on Patagonian fossil and extant material of the conifer Agathis. They report a suite of blotch mines, galls, scale-insect covers, and rust fungus that re-occur on the same host genus through time and space, showing the persistence of ecological guilds and possible host-tracking across major plate movements since the late Mesozoic. [ABSTRACT FROM AUTHOR]

A summary is presented of an article published online at http://dx.doi.org/10.1126/science.aaw5139 concerning the discovery of two fossils of the flowering plant family Fagaceae from the early Eocene in southern Argentina which are remarkably similar to Fagaceae currently found in North America.