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Premise: Acmopyle (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 with Acmopyle affinities from the early Eocene Laguna del Hunco site in Patagonia, Argentina. Methods: We studied 42 adpression leafy‐shoot fossils and included them in a total evidence phylogenetic analysis. Results: Acmopyle grayae sp. 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 of A. grayae shoots are compatible with the early stages of ovuliferous cone development. Our phylogenetic analysis recovers the new species in a polytomy with the two extant Acmopyle species. We report several types of insect‐herbivory damage. We also transfer Acmopyle engelhardti from the middle Eocene Río Pichileufú flora to Dacrycarpus engelhardti comb. nov. Conclusions: We confirm the biogeographically significant presence of the endangered West Pacific genus Acmopyle in Eocene Patagonia. Acmopyle is 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. [ABSTRACT FROM AUTHOR]

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. [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]

Premise: Two distinct types of fossil infructescences from the early Eocene Laguna del Hunco flora, Chubut Province, Patagonia, Argentina, preserve features of the family Cunoniaceae. The goal of the study was to assess their affinities within Cunoniaceae and to interpret their evolutionary and biogeographical significance. Methods: Specimens were collected from the Tufolitas Laguna del Hunco, Huitrera Formation. They were prepared, photographed, and compared morphologically with similar extant and fossil fruits and infructescences using published literature and herbarium material. Results: The fruit and infructescence morphology place the fossil taxa within Cunoniaceae. They do not conform to any extant genus, supporting the erection of two new fossil genera. Racemofructus gen. nov. shares diagnostic features of the tribe Cunonieae, especially Weinmannia s.l., and exhibits two tribal morphological synapomorphies: a racemose inflorescence and a replum composed of a single column. Cunoniocarpa gen. nov. specimens are paniculate inflorescences with basipetally dehiscent, bicarpellate capsules that have persistent styles and calyces. Its replum morphology suggests an affinity to the tribe Caldcluvieae, particularly to the genus Ackama. Conclusions: The new Patagonian fossils described herein constitute the oldest record of cunoniaceous capsules globally, supplementing a significant body of fossil evidence from pollen, wood, and reproductive structures from southern South America and Antarctica that suggests that the Cunoniaceae were diversified and widely distributed in the southern hemisphere by the early Eocene. Racemofructus and Cunoniocarpa are, respectively, the first fossil records from South America of reproductive structures with affinity to tribes Cunonieae and Caldcluvieae. [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 Methods Results Conclusions Fossil 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.Fossils 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.The 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.The 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. [ABSTRACT FROM AUTHOR]

Premise of research. Winteraceae, a family within the Canellales, is composed of tropical trees and shrubs broadly distributed in the Southern Hemisphere. The family is found today in eastern Australia, New Zealand, Malesia, Oceania, Madagascar, and the Neotropics across a range of dry to wet tropical to temperate climate regions. The fossil record of woods related to the Winteraceae in the Southern Hemisphere is limited to the Late Cretaceous of the Antarctic Peninsula. Here, we present a detailed anatomical description of the secondary xylem of a well-preserved trunk from the early Eocene Laguna del Hunco site, Huitrera Formation, Patagonia (Chubut Province, Argentina), that is referable to a new species of the genus Winteroxylon (Gottwald) Poole and Francis. Methodology. The wood is preserved as a siliceous permineralization; it was sectioned using standard petrographic techniques and observed under both light and scanning electron microscopy. The anatomy was compared with that of extant and fossil species of Winteraceae. Pivotal results. The diagnostic anatomical features of Winteraceae preserved in the fossil include an absence of growth rings, a lack of vessels, tracheids that are rectangular in cross section with circular bordered pits, diffuse axial parenchyma, rays showing two distinct size ranges (uniseriate-biseriate or multiseriate, 3–15 cells wide), and the presence of heterocellular rays containing sclerotic nests, cells with dark contents, and oil cells. The new fossil species most resembles extant genera within the Zygogynum s.l. clade from Australasian and Malesian rain forests; its anatomy is very similar to that of the extant genus Bubbia. The new Patagonian Winteraceae fossil wood is characterized by the presence of sclerotic nests and oil cells in the rays, which differ from those of previously described species of Winteroxylon. Conclusions. On the basis of the distinctive characters preserved, we erect Winteroxylon oleiferum sp. nov. The new fossil is the first reliable macrofossil record of Winteraceae from South America, supporting the abundant palynological record of the family from the continent, and it is the oldest record of the Zygogynum s.l. clade, adding to the long list of southern biogeographic connections between South America and Australasia via Antarctica during the warm early Cenozoic. [ABSTRACT FROM AUTHOR]

Here we present the first record of a stem-Coracii outside the Holarctic region, found in the early Eocene of Patagonia at the Laguna del Hunco locality. Ueekenkcoracias tambussiae gen. et sp. nov. consists of an incomplete right hind limb that presents the following combination of characters, characteristic of Coracii: relatively short and stout tibiotarsus, poorly developed crista cnemialis cranialis, short and wide tarsometatarsus, with the tuberositas m. tibialis cranialis located medially on the shaft, and curved and stout ungual phalanges. Although the presence of a rounded and conspicuous foramen vasculare distale and the trochlea metatarsi II strongly deflected medially resemble Primobucconidae, a fossil group only found in the Eocene of Europe and North America, our phylogenetic analysis indicates the new taxon is the basalmost known Coracii. The unexpected presence of a stem-Coracii in the Eocene of South America indicates that this clade had a more widespread distribution than previously hypothesized, already extending into the Southern Hemisphere by the early Eocene. Ueekenkcoracias tambussiae represents new evidence of the increasing diversity of stem lineages of birds in the Eocene. The new material provides novel morphological data for understanding the evolutionary origin and radiation of rollers and important data for estimates of the divergence time of the group. [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]

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]

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* 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]

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.

The Eocene Huitrera Formation of northwestern Patagonia, Argentina, is renowned for its diverse, informative, and outstandingly preserved fossil biotas. In northwest Chubut Province, at the Laguna del Hunco locality, this unit includes one of the most diverse fossil floras known from the Eocene, as well as significant fossil insects and vertebrates. It also includes rich fossil vertebrate faunas at the Laguna Fría and La Barda localities. Previous studies of these important occurrences have provided relatively little sedimentological detail, and radioisotopic age constraints are relatively sparse and in some cases obsolete. Here, we describe five fossiliferous lithofacies deposited in four terrestrial depositional environments: lacustrine basin floor, subaerial pyroclastic plain, vegetated, waterlogged pyroclastic lake margin, and extracaldera incised valley. We also report several new 40Ar/39Ar age determinations. Among these, the uppermost unit of the caldera-forming Ignimbrita Barda Colorada yielded a 40Ar/39Ar age of 52.54 ± 0.17 Ma, ~6 m.y. younger than previous estimates, which demonstrates that deposition of overlying fossiliferous lacustrine strata (previously constrained to older than 52.22 ± 0.22 Ma) must have begun almost immediately on the subsiding ignimbrite surface. A minimum age for Laguna del Hunco fossils is established by an overlying ignimbrite with an age of 49.19 ± 0.24 Ma, confirming that deposition took place during the early Eocene climatic optimum. The Laguna Fría mammalian fauna is younger, constrained between a valley-filling ignimbrite and a capping basalt with 40Ar/39Ar ages of 49.26 ± 0.30 Ma and 43.50 ± 1.14 Ma, respectively. The latter age is ~4 m.y. younger than previously reported. These new ages more precisely define the age range of the Laguna Fría and La Barda faunas, allowing greatly improved understanding of their positions with respect to South American mammal evolution, climate change, and geographic isolation. [ABSTRACT FROM AUTHOR]