Abstracts Virtual MPC

Abstracts (oral, posters) for Virtual MPC 2020 conference in alphabetical order.

Cell-searching: Did openness precede grass dominance in the Cenozoic assembly of Great Plains grasslands?

Alex Arrendale*, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA; USA Ellen Ng*, Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA; Will Brightly, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Regan Dunn, The La Brea Tar Pits and Museum, Los Angeles, CA, USA; Caroline A. E. Strömberg, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA

* alex1998@uw.edu, nhxeng@uw.edu

The spread of grasslands 26-22 million years ago has been linked to global climate changes in the late Oligocene to early Miocene. The pattern of vegetation change was established analyzing assemblages of microscopic plant silica (phytoliths) extracted from sediment samples from the Central Great Plains of North America. It is often presumed that as open-habitat grasses became abundant, vegetation structure concurrently transitioned from closed forests to open landscapes. However, recent work in the Cenozoic of Patagonia has pointed to a decoupling of grass dominance and habitat openness, each independently driven by climatic conditions. We set out to test if a similar decoupling occurred in the Central Great Plains by means of an a-taxonomic phytolith proxy using phytoliths produced in non-grass epidermal cells. Work in modern plants and soil assemblages has shown that the size and degree of undulation in these phytoliths (quantified by, respectively, Phytolith Area, PA, and the Phytolith Undulation Index, PUI) is correlated with the amount of light in the environment, reflecting habitat openness (measured as Leaf Area Index, LAI). We measure the PA and PUI of phytolith samples from Nebraska, dating 35 to 17 Ma, to reconstruct the regional LAI over time and place time constraints on the opening of habitats. By comparing this timeline to that of the rise to dominance of grasses, we hope to better understand changing vegetation and linked climatic conditions in Cenozoic North America.

Diversity of ancient cunninghamioid conifers (Cupressaceae): two new permineralized ovulate cones from the Upper Cretaceous of Hokkaido, Japan

Brian Atkinson, Department of Ecology and Evolutionary Biology and Biodiversity Institute, University of Kansas, Lawrence, KS, USA; Dori Contreras*, Perot Museum of Nature and Science, Dallas, TX, USA; Ruth A. Stockey, Gar W. Rothwell, Department of Botany and Plant Pathology, Oregon State University.

*dori.contreras@perotmuseum.org

Conifers representing the taxodiaceous grade of Cupressaceae were much more diverse and widespread during the Mesozoic than they are today. In particular, fossils associated with the earliest diverging extant subfamily, Cunninghamioideae, are found across the Northern Hemisphere and comprise at least ten genera. Cunninghamioid conifers are generally characterized by having seed cones with helically arranged bract-scale complexes, in which each complex is comprised of a foliate bract with a small, often membranous, free ovuliferous scale protruding from its adaxial surface. Here, two new cunninghamioid genera are characterized based on well-preserved permineralized seed cones from the Upper Cretaceous (Coniacian-Santonian) of Hokkaido, Japan. The two conifers display diagnostic seed cone characters typical of cunninghamioids; however, they have a mosaic of morphological and anatomical characters that are not seen in any previously reported conifer of the Cupressaceae. They are therefore designated as two new extinct genera. These new conifers expand the taxonomic and morphological diversity of cunninghamioid conifers during the Mesozoic, and further demonstrate the high diversity of the family in Upper Cretaceous of Japan. The occurrence record of similar fossil Cupressaceae conifers with foliate seed cones (including cunninhamioids, Tawainia and similar fossil taxa) suggests a peak in diversity during the mid-Jurassic through Cretaceous, with taxa mostly distributed across the Northern Hemisphere. The living genera Cunninghamia and Taiwania appear during that time, and maintain a nearly continuous record through today, while nearly all other Cupressaceae genera with foliate cones disappear by the end Cretaceous. The recognition here of two new distinct conifers from the already diverse Upper Yezo Group of Japan demonstrates the importance of morphologically diverse, yet closely related, cunninghamioid conifers in structuring ecosystems during that time.

Paleoclimate and paleoecological reconstructions of the early Miocene Hiwegi Formation, Rusinga Island, Lake Victoria, Kenya

Aly Baumgartner* & Daniel J. Peppe; Terrestrial Paleoclimatology Research Group, Department of Geosciences, Baylor University, Waco, TX, USA

*aly_baumgartner@baylor.edu

The Early Miocene of Rusinga Island (Lake Victoria, Kenya) is best known for its vertebrate fossil assemblage, particularly of early apes. In addition to these vertebrate faunas, there are three stratigraphic intervals with well-preserved fossil leaves in the Hiwegi Formation that have received much less attention: Kiahera Hill (~18.3 ma), R5 (~18.1 ma), and R3 (~17.8 ma). We assessed the floral composition, diversity and paleoclimate of the Kiahera Hill and R3 localities. The Kiahera Hill and R3 floras have significantly different taxonomic compositions. The Kiahera Hill flora had few monocots or herbaceous taxa and was dominated by large leaves, which suggests a warm, forested environment. The R3 flora was spatially heterogeneous with monocots and herbaceous taxa found dominating patches on the landscape and reed-like monocots and emergent aquatics which indicate at least periodic standing water at the site. In addition to differences in composition, the Kiahera Hill flora had a higher species richness and greater evenness than the R3 flora. The mean annual temperature (MAT) and mean annual precipitation (MAP) of Kiahera Hill is reconstructed to be 31.7 °C and 1812-3577 mm/yr, respectively, which indicates a transitional tropical seasonal forest-tropical rainforest biome. The MAT and MAP of R3 is reconstructed to be 17-23.5 °C and 858-1760 mm/yr, respectively, which indicates a transitional woodland-tropical seasonal forest biome. Further, these estimates are slightly cooler and drier than previous estimates. These results demonstrate that there was a considerable change in both climate and vegetation over an ~500 kyr interval between the Kiahera Hill and R3 floras. Thus, this work, coupled with previous research, suggests that the Hiwegi Formation on Rusinga Island samples multiple environments in the Early Miocene, which in turn likely influenced the evolution and habitat preferences of early apes.

Pollen malformations as indicators of past environmental stress: Comparing background variation with heightened UV-B exposure in modern conifers

Jeffrey Benca*, Amazon Spheres and Burke Museum of Natural History and Culture, Seattle WA *jbenca@uw.edu

Widespread malformations in fossilized saccate (winged) pollen of gymnosperms have been proposed as a biological stress response during the end-Permian crisis (252 Ma). However, it is not well established how frequently, variably or consistently pollen malformations are expressed across modern gymnosperm lineages under near-optimal conditions or environmental stress. To evaluate the utility of pollen malformations as a paleoenvironmental stress indicator, we compared their frequency and variation in pollen yields spanning 14 conifer genera of Pinaceae and Podocarpaceae sampled from lowland gardens of the United States under near-optimal conditions. Although malformations comprise <3% of pollen yields in 12 of the 13 bisaccate genera studied, they represent >10% of yields in the only trisaccate lineage analyzed, Dacrycarpus dacrydioides under near-optimal conditions. We detected no phylogenetic pattern in the types of malformations expressed between bisaccate lineages in the baseline comparison. Additionally, the baseline pollen yields were compared with those produced by Pinus mugo “Columnaris” grown under an abiotic stress- specifically three experimentally heightened UV-B regimes proposed for the end-Permian crisis. UV-B irradiated P. mugo produced significantly higher frequencies of malformations and the type of malformations expressed deviated from bisaccate lineages under garden settings. These results suggest that (1) bisaccate pollen types maintain a high degree of morphological conservatism under present near-optimal growth conditions while trisaccate pollen types do not, and (2) environmental stress can significantly alter the frequency and expression of malformations in modern conifers relative to near-optimal conditions. Based on these results, malformation frequencies exceeding 3% in bisaccate pollen yields can be used as an indicator of paleoenvironmental stress while trisaccate lineages are not suitable for such assessments.

Uncovering Mesozoic peat moss diversity: permineralized Sphagnopsida (Bryophyta) from the Late Cretaceous of Vancouver Island, Canada

Alexander Bippus*, Department of Botany and Plant Pathology, Oregon State University, OR, US; Gar Rothwell, Department of Botany and Plant Pathology, Oregon State University, OR, USA / Department of Environmental and Plant Biology, Ohio University, OH, USA ; Ruth Stockey, Department of Botany and Plant Pathology, Oregon State University, OR, USA

*bippusa@oregonstate.edu

Peat mosses (class Sphagnopsida) are an ecologically and morphologically distinctive group of plants that are a major component of cool, temperate biomes worldwide. The unique anatomy, morphology, and biochemistry of Sphagnum (which accounts for >95% of the diversity within the class) allows plants to absorb >25x their dry weight in water and to thrive in environments with low pH and nitrogen availability; thereby perpetuating water-logged, acidic, and nutrient-poor environments that exclude other plants. This capacity to act as an “ecosystem engineer” enables Sphagnum peatlands to occupy nearly 3% of the land surface of Earth and to form extensive peat deposits that store >25% of global soil carbon. In doing so, peat mosses exert significant influence on global climate and carbon cycles. Phylogenetically, the Sphagnopsida occupies an early-diverging position among mosses. Surprisingly, the pre-Cenozoic fossil record of the lineage consists of an Ordovician report of Sphagnum gametophytes and several Mesozoic reports of Sphagnum spores. Here, we present the first Mesozoic peat moss gametophytes. These fossils consist of >35 small fragments of permineralized, dichotomously branching leafy shoots with sphagnopsid anatomy. They were discovered in calcium carbonate concretions collected from Late Cretaceous (Santonian/Campanian) sediments along the banks of the Tsolum River on Vancouver Island, Canada. Two anatomically distinct peat moss morphotypes can be recognized from this material. The first morphotype has stems with multiple layers of hyalocysts (inflated epidermal cells), some of which resemble specialized water storage cells found in extant Sphagnum species (retort cells), whereas stems of the second morphotype have a single hyalocyst layer which lacks retort cells. Today, modern peat mosses often grow in mixed-species communities. The discovery of these two syngenetic sphagnopsid morphotypes reveals that Sphagnum diversification was well underway by the Cretaceous, and tentatively suggests that this aspect of peat moss ecology has been retained since the Mesozoic.

Evolutionary Drivers of Seed Dispersal Strategy in Poaceae

William Brightly* & Caroline Strömberg, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA

*whbright@uw.edu

Seed dispersal is a crucial biological process for plants and their communities, affecting range size, population connectivity, and responses to climate change and other perturbations. Grasses possess a remarkable diversity of seed dispersal strategies, and the success of some cosmopolitan species is classically attributed to their capacity for effective seed dispersal (e.g., Phragmites australis). Habitats dominated by grasses are of global importance, and their mid-late Cenozoic expansion was one of the most consequential events of the last 66 million years. This transition undoubtedly had ecological consequences, including numerous changes to potential seed dispersal agents for grasses living in these regions (e.g., faunal turnover, exposure to wind). Given that different habitats are associated with a different suite of potential dispersal agents, we test whether changes in habitat occupation precipitated evolutionary changes in dispersal strategy in grasses occupying early grasslands in North America.

To do so, we collected a reference set of modern diaspores (unit of seed dispersal) from species spanning the extant phylogenetic and functional diversity of the grass family. Fossil diaspores were collected from eight sites ranging in age from the early to late Miocene of Kansas and Nebraska. These primarily consist of silicified anthoecia of the tribe Stipeae (needle grasses). Diaspore characters related to different dispersal strategies (mass, callus type, shape, surface roughness, falling velocity), and species habitat were recorded. Using a preliminary dataset, we tested for correlated evolution between habitat type and dispersal characters. Results did not support the hypothesis that transitions into grassland habitats were associated with changes in seed dispersal strategy, though disturbed habitats apparently promote the evolution of traits associated with wind dispersal. We are currently working on expanding our modern dataset, and incorporating fossil taxa to further test these patterns, and document changes during the early-late Miocene spread of grasslands in North America.

Habitat-Driven Evolution of Seed Dispersal Strategies in Onion Grasses

McKenzie Carlson*, Will Brightly, & Caroline Strömberg, University of Washington Department of Biology and Burke Museum of Natural History, Seattle, WA, USA

*mck2022@uw.edu

Seed dispersal is a crucial phase of plant lifecycles. Effective dispersal is important to the ecosystem as a whole because it affects composition of the community, ecological succession, and response to climate change. Given the importance of seed dispersal, understanding the factors that contribute to the evolution of varied dispersal modes and promote convergence on specific dispersal strategies is particularly important to understanding grass ecology because it may allow us to understand the relationship between dispersal mode and habitat. In this study, we are interested in dispersal modes within the onion grasses (Melica), a small genus of perennial grasses, primarily distributed in temperate regions. The onion grasses are found in a wide variety of habitats and possess a remarkable diversity of seed dispersal strategies. These traits make them a useful case study for better understanding the factors that influence the evolution of dispersal strategies in grasses. We are testing the hypothesis that evolution in traits associated with seed dispersal is correlated with changes in habitat. In particular, we hypothesize that the evolution of wind dispersed seeds follows transitions into open habitats.

Seed dispersal structures (diaspores) were collected from 46 grass species (36 Melica and 11 outgroup). To assess wind dispersal potential, we quantify falling velocity by filming seed descent at 1000 fps. Lower falling velocities are associated with higher wind dispersal potential. Diaspores were photographed and the images were used to measure surface roughness, which is associated with adhesive dispersal potential. These data, along with diaspore mass and plant height, were mapped onto the evolutionary tree of the onion grasses. We then ran tests of correlated evolution between seed dispersal traits and habitat type. Initial results indicate that convergence upon wind dispersal may be in part driven by convergence upon disturbed habitat types.

Exceptional greening of mid-latitude ecosystems during Cenozoic warm intervals

Jeremy K., Caves Rugenstein*, Department of Geosciences, Colorado State University, CO, USA; Alexander Winkler, Max Planck Institute for Meteorology, Hamburg, Germany; Samuel H. Kramer, Department of Geological Sciences, Stanford University, Stanford, CA, USA; Tyler Kukla, Department of Geological Sciences, Stanford University, Stanford, CA, USA; Daniel E. Ibarra, Department of Earth and Planetary Sciences, University of California, Berkeley, CA, USA; Alexis Licht, Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA; Page Chamberlain, Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA

*Jeremy.Rugenstein@colostate.edu

There are few direct constraints on how primary productivity has varied in the geologic past. However, as one of the fundamental measures of ecosystem energy and mass transfer, understanding how primary productivity changes in response to higher CO₂ may yield insights into how ecosystems respond to changing atmospheric CO₂, how terrestrial water availability may vary in a warmer climate, and how biodiversity is affected by productivity. To obtain spatially and temporally extensive estimates of mid-latitude primary productivity change during past greenhouse periods, we use a large, global database of paleosol carbonate δ¹³C (>8,000 samples) from the Cenozoic to estimate changes in primary productivity and concomitant changes in water use efficiency across the mid-latitudes. The δ¹³C of soil carbonate in C₃ ecosystems reflects the partial pressure of soil-respired CO₂—which to first-order is controlled by primary productivity—due to the distinctly negative ¹³C values of organic matter. Overall, paleosol ¹³C in nearly all localities either increases or remains constant over the course of the Cenozoic. This long-term increase and/or constancy of ¹³C indicates a substantial decrease in plant productivity—by a factor of 3 to 10—as atmospheric pCO₂ declined over the Cenozoic, with the largest decreases in productivity in the most arid locations today. Using independent estimates of precipitation during these past greenhouse periods, we speculate that productivity is more sensitive to atmospheric CO₂ than precipitation in the mid-latitudes, resulting in lower runoff despite a greener landscape during periods of high atmospheric CO₂. These results indicate that several characteristics that today define ecosystems—such as water availability and productivity—may be temporally decoupled.

Dispersal Biology and Patterns of the Involucral Morphology of Palaeocarpinus

Julian Correa* & Steve Manchester, Florida Museum of Natural History University of Florida, Gainesville, FL, USA

* j.correanarvaez@ufl.edu

Palaeocarpinus is an extinct genus of fruit treated within the betulaceous subfamily Coryloideae. The genus shares traits with two of the more prominent members of the subfamily – a small longitudinally ribbed nutlet (Carpinus-like) subtended by a pair of involucral bracts (Corylus-like). Palaeocarpinus has distinctive bract morphologies that varies among species; some members have spiny margins that could cling to the fur or feathers while others have broad or long webbed bracts that could easily serve as ‘wings’ for catching wind. We investigated the possible scenarios for the dispersal of each bract ‘type,’ compared them to modern genera and considered the physics of dispersal methods inferred from the wing surface area and dissection in relation to the nutlet size and weight. Molecular studies of the phylogeny of modern Corylus have yielded trees with clades matching their bract types. We tested to see if Palaeocarpinus phylogenetic analyses, using a morphological matrix, would yield comparable results concerning bract variation. Preliminary results produced tree topologies with low support and branches which easily collapse into polytomies; further investigation into this is required to better understand the plasticity of bract variation. Continuing investigation of Palaeocarpinus morphology and diversity may provide important insights into our understanding of evolutionary patterns that have shaped diversification and dispersal strategies in the Betulaceae.

Habitat heterogeneity and vegetation response to the Middle Miocene Climatic Optimum in the Santa Cruz Formation (Patagonia)

Camilla Crifò*, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; M. Susana Bargo, División Paleontología de Vertebrados, Anexo Museo de La Plata, CIC, CONICET, La Plata, Argentina.; Jose I. Cuitiño, Instituto Patagónico de Geología y Paleontología (IPGP) CENPAT-CONICET, Puerto Madryn, Chubut, Argentina; Richard F. Kay, Department of Evolutionary Anthropology, Duke University, Durham, NC, USA; Matthew J. Kohn, Department of Geosciences, Boise State University, Boise ID, USA; Robin B. Trayler, Department of Life & Environmental Sciences University of California, Merced, CA, USA; Sergio F. Vizcaíno, División Paleontología de Vertebrados, Anexo Museo de La Plata, CIC, CONICET, La Plata, Argentina.; Alejandro F. Zucol, Laboratorio de Paleobotánica, CICYTTP-Diamante (CONICET), Diamante, Argentina; Caroline A. E. Strömberg, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA

*camilla.crifo@gmail.com

The Middle Miocene Climatic Optimum (MMCO; ca. 17–14.5 Ma) is the most recent Cenozoic global warming event. It affected ecosystems that were broadly comparable to today’s, making it one of our best analogues for ongoing, anthropogenic climate change. Whereas vegetation responses to the MMCO in the northern hemisphere are well documented, southern hemisphere changes are poorly known. We use phytolith analysis to study the southernmost record of ecosystem change during the onset of the MMCO from fossiliferous horizons in the Atlantic coastal localities of the Santa Cruz Formation (SCF), Santa Cruz Province, Argentina. We infer vegetation change through time using samples collected through a vertical section, as well as multiple phytolith assemblages from a single stratigraphic level across several localities. This lateral sampling allows us to test the hypothesis that high faunal diversity at the onset of the MMCO was linked to habitat heterogeneity, presumably driven by niche differentiation. We then compare our result to faunal assemblages and climate proxy data from the SCF. Our record suggests that vegetation was distinctly heterogeneous during the MMCO global warming event, consistent with our hypothesis. Our study represents the first time that spatial variation in local vegetation during this event has been tested using direct paleobotanical evidence. Moreover, vegetation at the coast differed sharply from other inland early Miocene Patagonian sites, pointing to additional, regional heterogeneity in vegetation structure and response to climate change. Our data also suggest that plant communities responded in a non-analogue way to global warming and aridification, with an increase in open, dry-adapted vegetation dominated by xerophytic woody taxa (shrubland) rather than grasses (grassland). We interpret dominant taxa in SCF grass communities as C₃ (temperate) grasses that were not adapted to dry conditions, consistent with the hypothesis that open, grass-dominated habitats did not expand in Patagonia until after the early middle Miocene.

A new earliest Paleocene, mountain proximal, mature forest floor fossil leaf site in the Denver Basin, Colorado, USA

V.F. Crystal*, Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, USA / Denver Museum of Nature & Science, Department of Earth Sciences, Denver, CO, USA; I.M. Miller, Denver Museum of Nature & Science, Department of Earth Sciences, Denver, CO, USA

*victoria.crystal@colorado.edu

North America’s Western Interior Basin Cretaceous floras were diverse and heterogenous, while Paleocene floras were depauperate and homogeneous. Conventional thinking argued that forest diversity did not recover until the Early Eocene, ~10 Ma after the K-Pg extinction. However, this paradigm shifted with the discovery of the heterogeneous and high diversity early rainforest (ca. 64 Ma) in 1994 in the Denver Basin, Colorado. The remarkable composition and heterogeneity of the Castle Rock flora is hypothesized to result from two factors: 1) the proximity of the site to the topographic front on the western edge of the Basin resulting in intensified orographic rainfall, and 2) its unusual taphonomic setting, where overbank deposits buried a mature forest floor. A series of new mountain proximal, earliest Paleocene (~10 m above the K-Pg boundary; ca. 65.8 Ma), mature forest floor deposits (including in situ tree stumps) preserving megaflora were recently discovered and excavated in the Denver Basin. Over 1,500 fossil leaves were censused from 6 quarry sites spanning a ~50 meter exposure that preserved 4 distinct forest floor horizons. Together, the flora contain 12 angiosperms, 2 ferns, and 3 seeds/reproductive parts. The taxa include characteristic Early Paleocene plants including dominant dicots“Rhamnus” goldiana, Platanus raynoldsii, and “Zizyphus” sp., minor dicots “Ficus” planicostata, “Artocarpus” lessigiana, cf. “Vitis” stantoni, Paleonelumbo macroloba, and three unidentified species. Monocots include Sabalites sp. and cf. Paloreodoxites plicatus; ferns include Allantodiopsis erosa and Onoclea sp. Leaf sizes indicate a rainfall of ~2.9 m +126/-88 cm (1 SE). The “Rhamnus” goldiana specimens exhibit a leaf physiognomy similar to “Rhamnus” leaves from the Castle Rock site. The new site shows a high spatial heterogeneity in the dominance of taxa between quarries. Overall, the new site indicates that while diversity was markedly low, there was spatial heterogeneity present in forests within approximately 200,000 years following the K-Pg boundary.

Terrestrial Ecosystem Response to the Cretaceous-Paleogene Boundary: Case Study from the San Juan Basin, New Mexico, USA

Andrew Flynn*, Department of Geosciences, Baylor University, Waco, TX, USA; Ross Secord, Department of Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA; Jie Geng, Department of Geosciences, Baylor University, Waco, TX, USA; Brittany Abbuhl, Department of Geosciences, Baylor University, Waco, TX, USA; Thomas Williamson, New Mexico Museum of Nature and Science, Albuquerque, NM, USA; Stephen Brusatte, School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom; Daniel J. Peppe, Department of Geosciences, Baylor University, Waco, TX, US

*Andrew_Flynn@Baylor.edu

Early Paleocene floral communities were substantially restructured as a result of the Cretaceous-Paleogene (K-Pg) mass extinction approximately 66.0 Ma. While events immediately adjacent to the K-Pg boundary have been extensively studied, comparatively little research has looked at long-term terrestrial ecosystem recovery during the early Paleocene. The San Juan Basin (SJB), located in northwestern New Mexico, preserves an exceptional, large, and well-dated early Paleocene plant record making it an ideal location to study long-term recovery of early Paleocene terrestrial ecosystems. Here we investigate early Paleocene terrestrial ecosystem change using a coupled high-resolution plant and δ¹³C record from the SJB.

Plant macrofossils were collected from the lower Paleocene Ojo Alamo Sandstone and lower Nacimiento Formation in the SJB spanning the initial ~1.5 myr of the Paleocene. Macrofloral extinction, origination, and net diversification rates were simultaneously estimated using the Pradel capture-mark-recapture (CMR) model from 66.0 – 64.5 Ma with 100 Kyr time-steps. Two intervals of decreasing floral diversity were identified: a short interval at ~65.5 Ma and a prolonged interval from ~65.2 – 64.7 Ma. Two short intervals of rapidly increasing floral diversity were also identified: the first at ~65.3 Ma and the second at ~64.6 Ma. The onset of both intervals of decreasing floral diversity are coeval with a -1.5 to -2.5 ‰ bulk organic δ¹³C excursion. We also applied the Pradel CMR model to contemporaneous macrofloras from the Denver Basin (DB), Colorado and the Williston Basin (WB), North Dakota and Montana. The floral diversity patterns estimated from the DB and WB indicate intervals of increasing and decreasing floral diversity that are coeval with the same intervals identified in the SJB. This suggests a regional driver in patterns of floral diversity change during the early Paleocene in western North America, which reflects prolonged terrestrial ecosystem instability following the K-Pg mass extinction.

Shedding light on the evolutionary history of grasses through automated, quantitative imaging analyses of plant silica (phytolith) fossils

Timothy J. Gallaher*, Department of Biology and Burke Museum of Natural History, University of Washington Seattle WA, USA and Bishop Museum, Honolulu, HI, USA; Claire Grant, Department of, University of Washington Seattle WA, USA; Kari Jessett, Department of Biology, University of Washington Seattle WA, USA; Phil Klahs, Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames IA, USA; Claire Marvet, Department of Biology, University of Washington Seattle WA, USA; Xiangyun Meng, Department of Computer Science and Engineering, University of Washington, Seattle, WA, USA; Jessica Perry, Department of Statistics, University of Washington, Seattle, WA, USA; Oakley Reid, Department of Biology, University of Washington Seattle WA, USA; Ashley Senske, Department of Biology, University of Washington Seattle WA, USA; Silishia Wong, Department of Biology, University of Washington Seattle WA, USA; Kailyn Zard, Department of Biology, University of Washington Seattle WA, USA; Callie Zender, Department of Biology, University of Washington, Seattle, WA, USA; Jifan Zhang, Department of Computer Science and Engineering, University of Washington, Seattle, WA, USA; Lynn Clark, Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames IA, USA; Kevin Jamieson, Department of Computer Science and Engineering, University of Washington, Seattle, WA, USA; Caroline A.E., Strömberg, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA

*tgalla@uw.edu

The evolution of grasses and assembly of the grassland biome during the Cretaceous and Cenozoic vitally transformed Earth’s terrestrial ecosystems, but the timing and geographic contexts of these changes have been difficult to reconstruct because of the scarcity of informative grass macrofossils. Recent research using phytoliths has helped shed light on this key evolutionary and ecological series of events. However, gaining further insight into the evolutionary and biogeographical history of Poaceae depends critically on refined methods to identify specific grass lineages in the fossil record. Current methods for taxonomically placing grass phytoliths, so-called grass silica short cell phytoliths (GSSCP) are imprecise and subjective, employing qualitative shape traits and “expert” opinion, and attempts at solving this problem using quantitative measurements of GSSCP shape have failed to come up with accurate, precise, and practical solutions. Our research aims to enhance the use of GSSCP for robust taxonomic and ecological interpretations by developing two independent, quantitative, and objective ways of assessing taxonomic or phylogenetic affinity of fossil GSSCP: (I) Machine Learning and Computer Vision (ML&CV) analysis of 2D images; and (II) Landmark-Based Geometric Morphometrics (LBGM) on 3D images. We are currently assembling large databases of (1) 2-D brightfield images of GSSCP; and (2) 3-D models based on confocal images of stained GSSCP from 200 taxa from across the Poaceae phylogeny. We couple this work with phylogenetic mapping of functionally relevant traits (e.g., photosynthetic pathway, growth form) and environmental preferences. Our methods will vitally expand the number of taxonomically (and ecologically) well-placed fossils used for phylogenetic dating, biogeographic analysis, and ecological characterization of ancient grass communities. As part of this project, we are also developing a website (PhytAID) that provides a common platform for the automatic identification of grass phytoliths using the two independent methods (ML&CV, LBGM).

A preliminary study of Early Devonian pyrite permineralized stems by Micro-CT scanning

Patricia G. Gensel*, Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Selena Y. Smith, Department of Earth and Environmental Sciences and Museum of Paleontology, University of Michigan, Ann Arbor, MI, USA

*pgensel@bio.unc.edu

Several approaches to studying the anatomy of Devonian plants from pyritized specimens exist, with results from each depending on the extent of plant cell wall preservation and aspects of pyrite formation. Etched and polished thin sections usually provide considerable information but even better are peels – less material is lost between sections, more detailed structures are shown – as was done for Armoricaphyton (e.g., Gerrienne and Gensel 2016). Critical to this appears to be both a comparatively small degree of cell wall degradation or destruction and how the permineralization occurred; in particular, in specimens with more details, the pyrite appears more cohesive and perhaps with a smaller crystal size.

Attempts to generate informative peels from several taxa from the Early Devonian of Canada (New Brunswick and Gaspé) were inconsistent or unsuccessful. It appears cell walls are less well preserved and much of the pyrite is less intact. Etched and polished sections yield considerable information, but the small axis size (2-5 mm) makes it difficult to cut in desired planes. We therefore examined examples of 4 different plant types of trimerophyte grade organization, with micro-CT scanning to see if more can be learned. Specimens were scanned on a Nikon XTH 225ST industrial microCT scanner at the University of Michigan, yielding tomograms with voxel sizes of 7.1 to 11.7 µm. Scan data were processed using Avizo computer software. The Gaspé specimens included axes from two plants tentatively attributable to Psilophyton and one as yet unnamed new genus, and the New Brunswick specimens are from the new plant with secondary xylem. Two examples will be shown.

Results are informative, most particularly concerning isotomous branching or lateral trace formation. Finer details, such as protoxylem cell shape or presence of rays, were less visible, in part due to resolution at which they were done, or taphonomy.

Most interesting thus far are aspects of taphonomy that are revealed from the stack of 2000 tomograms. Major areas of degradation are more prominent than when going through series of sections. Some axes that appeared as part of a single branching system were found, when observed in 3D, to be unrelated. Other interesting aspects of orientation of axes and of taphonomic effects also were observed and can be compared to better understand features observed by thin section techniques. Micro-CT scanning, in conjunction with standard thin sections, promises to provide a more multidimensional and accurate view of anatomical changes in critical regions of these early plants.

Fossil woods from the middle Miocene of Myanmar: implications for the evolution of Dipterocarpaceae

Nicolas Gentis*, CR2P, UMR7207, MNHN, Sorbonne Université, CNRS, Paris, France; Alexis Licht, Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA; Anaïs Boura, CR2P, UMR7207, MNHN, Sorbonne Université, CNRS, Paris, France; Dario De Franceschi, CR2P, UMR7207, MNHN, Sorbonne Université, CNRS, Paris, France; Za Win, Geology Department, Shwe Bo University, Sagaing Region, Myanmar; Day Wa Aung, Geology Department, University of Yangon, Pyay Rd, Yangon, Myanmar; Guillaume Dupont-Nivet, Géosciences Rennes, UMR CNRS 6118, Univ. Rennes, Rennes, France/ Institute of Earth and Environmental Science, Potsdam University, Potsdam, Germany/ Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, Beijing, China

*nicogentis@gmail.com

The paleobotanical record of Myanmar is poorly documented despite its importance for understanding the evolution of Asian rainforests, often dominated today by Dipterocarpaceae. The middle Eocene of Myanmar has yielded some of the earliest Dipterocarpaceae of the paleobotanical record, associated with seasonally dry forests that are today common in monsoonal areas of India. Here, we describe 17 species of fossil woods (including 4 new species) collected in the middle Miocene Natma Formation, central Myanmar. These species share affinities with modern Fabaceae, Dipterocarpaceae, Burseraceae, Moraceae and Cupressaceae. They include a great variety of fossil dipterocarps (7 species) similar to the one found in modern rainforests of peninsular Southeast Asia. The presence of fossil dipterocarp species typical of wet evergreen forests contrasts with Burmese Eocene dry dipterocarp assemblages and indicates wetter conditions in the Miocene. Our paleoenvironmental reconstructions support a late Paleogene adaptation of dipterocarps to everwet ecosystems, as suggested by previous physiological and biogeographic studies.

Exploring diversity through morphology: Morphometrics and X-ray Computed Tomography of a new fossil Heliconia from the Miocene of Panama

Ashley M. Hamersma*, Department of Earth and Environmental Sciences, University of Michigan, MI, USA; Selena Y. Smith, Department of Earth and Environmental Sciences, University of Michigan, MI, USA; Molly Ng, John C. Benedict, Department of Earth and Environmental Sciences, University of Michigan, MI, USA; Fabiany Herrera, Chicago Botanic Garden, Chicago, IL, USA; and Carlos Jaramillo, Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama

*cyanash@umich.edu

Morphology and anatomy are crucial to understanding relationships between fossil & extant organisms. Heliconia, monocots commonly known as the ‘lobster-claws,’ are neotropical herbaceous plants of the monogeneric Heliconiaceae, in the order Zingiberales. Heliconia has no published, reliable fossil record, but morphological characterization of extant Heliconia will help to recognize potential fossil material. Here, we aim to describe and phylogenetically place a new fossil taxon hypothesized to belong to the Heliconiaceae, and to explore the efficacy of using landmark-free 3D morphometrics to characterize fossil and extant material. Fossil material used in this study comprises abundant, anatomically preserved seeds from the Cucaracha Formation of Panama, an early Miocene (~19 Ma) locality. Comparative data on extant Heliconia pyrenes was collected from 72 of 201 species, with all clades and subgenera represented. All specimens were studied via X-ray tomography and analyzed with Avizo. Morphological characters identified from studying 3D reconstructions were used to examine trait distribution in the context of a recent molecular phylogeny. We found that seed morphology is fairly uniform with a high degree of homoplasy except for an early-divergent clade of Pacific Island and Ecuadorian species that show distinct morphology. This is similar to vegetative and floral traits in modern Heliconia; species share a high degree of morphological similarity, with the exception being inflorescence morphology. Floral morphology has been shown to be homoplasious, with a proposed basis in pollinator interactions. While seed structure confirms the placement of the fossils within Heliconiaceae, phylogenetic analyses are largely unable to place the fossil within the phylogeny due to the high homoplasy. Confirming that these Cucaracha fossils are in the Heliconiaceae demonstrates the presence of the family in Central America at least since the early Miocene, before the closing of the Central American Seaway, and adds to our understanding of past Neotropical diversity.

Reconstructing spatio-temporal patterns of vegetation change in the Permian of Gondwana: a model-based palynological approach

Reilly Hayes*, Department of Integrative Biology, University of California / UC Museum of Paleontology, Berkeley, CA, USA; Cindy Looy, Department of Integrative Biology, University of California / UC Museum of Paleontology / UC & Jepson Herbaria, Berkeley, CA, USA

*reilly_hayes@berkeley.edu

Understanding spatial patterns of vegetation change through time represents a basic goal of paleobotany, yet poor temporal control over fossil assemblages, compounded by sparse and biased geographic and environmental coverage, makes the task notoriously challenging. A common solution is to sort fossils into stage-level or even coarser time bins, and thereafter treat occurrences within each bin as contemporaneous. While easy to implement, this treatment produces timescales capable of capturing at best broad trends of floral change, and often muddies co-occurrence data by purging assemblages’ local stratigraphic and environmental context.

Here we outline a model-based approach to reconstructing phytogeographic evolution in deep time, and offer a preliminary implementation in the Permian of Gondwana. This system provides a well-constrained geochronological framework: fossiliferous Permian basins of Australia boast 79 high precision U-Pb CA-TIMS dates, as well as several—albeit less precise—SHRIMP dates. African and South American basins provide at least an additional 39 CA-TIMS and SHRIMP dates. Crucially, the studies that produced many of these dates document explicit stratigraphic relationships with palynological zonations, allowing them to directly calibrate the tempo of vegetation change.

This quantitative framework is employed to reconstruct responses of Gondwanan floras to major environmental change in the late Paleozoic—namely, the early to middle Permian deglaciation and aridification, and the end-Permian terrestrial biotic crisis. Although we here focus upon pollen and spore data directly correlated to the U-Pb dates, an expanded treatment integrating the botanical affinity of the palynomorphs and their associated macrofossil assemblages is forthcoming.

Reconstructing Krassilovia mongolica supports recognition of a new and unusual group of Mesozoic conifers

Fabiany Herrera^*, Chicago Botanic Garden, Glencoe, IL, USA ; Gongle Shi, State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing People’s Republic of China; Chris Mays, Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden / School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria , Australia; Niiden Ichinnorov, Institute of Paleontology and Geology, Mongolian Academy of Sciences, Ulaanbaatar, Mongolia; Masamichi Takahashi, Department of Environmental Sciences, Faculty of Science, Niigata University, Ikarashi, Nishi-ku, Niigata, Japan; Joseph J. Bevitt, Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales, Australia; Patrick S. Herendeen, Chicago Botanic Garden, Glencoe, IL, USA Peter R. Crane, Oak Spring Garden Foundation, Upperville, VA, USA / School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA

*fherrera@chicagobotanic.org

Previously unrecognized anatomical features of the cone scales of the enigmatic Early Cretaceous conifer Krassilovia mongolica include the presence of transversely oriented paracytic stomata, which is unusual for all other extinct and extant conifers. Identical stomata are present on co-occurring broad, linear, multiveined leaves assigned to Podozamites harrisii, providing evidence that K. mongolica and P. harrisii are the seed cones and leaves of the same extinct plant. Phylogenetic analyses of the relationships of the reconstructed Krassilovia plant place it in an informal clade that we name the Krassilovia Clade, which also includes Swedenborgia cryptomerioides–Podozamites schenkii, and Cycadocarpidium erdmanni–Podozamites schenkii. All three of these plants have linear leaves that are relatively broad compared to most living conifers, and that are also multiveined with transversely oriented paracytic stomata. We propose that these may be general features of the Krassilovia Clade. Paracytic stomata, and other features of this new group, recall features of extant and fossil Gnetales, raising questions about the phylogenetic homogeneity of the conifer clade similar to those raised by phylogenetic analyses of molecular data.

The history and diversity of plane trees (Platanaceae) with unlobed leaves in the Paleogene of North America

Indah Huegele*, Florida Museum of Natural History, Gainesville, FL, USA

*indah.huegele@gmail.com

The plane tree family has an extensive fossil record dating back to the middle Albian with more than a dozen genera and at least 140 recognized fossil species. Many of these extinct members had primarily unlobed leaves, which is a rare feature among living species. In Late Cretaceous floras of Siberia, Alaska, and Canada, such unlobed taxa were highly abundant and dominated these assemblages. However, unlobed platanoids from outside the Siberian-Canadian paleofloristic region have received relatively little attention. Here, we confirm the presence of Platimeliphyllum in Oregon and Washington using a suite of morphological characters. Overall lamina shape, L:W ratio, symmetry, base and apex shape, tooth type and variability, strength of basal veins compared to secondary veins, basal vs. suprabasal divergence of basal veins, number of pairs of secondary veins, angle of secondary veins from midvein, number of agrophic veins, strength of epidermal striations, and abundance of trichome bases among other characters are useful for differentiating unlobed platanaceous species. Our preliminary observations further suggest that many leaves described as Betula iddingsii from the Eocene of Yellowstone, Betulites sp. from the Late Cretaceous Dakota Sandstone of Kansas, and Langeria magnifica from the Eocene of Republic, Washington, may also represent species of extinct, unlobed Platanaceae. In addition, Dyrana, a platanoid genus established for unlobed, lanceolate, densely toothed leaves from the Maastrictian-Danian of the Koryak Upland in northeastern Siberia is likely congeneric with specimens previously attributed to “Meliosma” and other genera from Paleocene or Eocene deposits in Washington, Montana, Wyoming, North Dakota, and Greenland. These records, along with previously described records of Protophyllum from North Dakota, suggest that unlobed Platanaceae were diverse and widespread during the Paleogene in North America. However, a more detailed investigation of North American material is needed to fully confirm the identities of unlobed Platanaceae in these floras.

A Bayesian approach to estimating the phylogeny of Azolla

Nathan A. Jud*, Department of Biology, William Jewell College, MO, USA; Facundo De Benedetti, Museo Paleontológico Egidio Feruglio, CONICET, Trelew, Argentina; Elizabeth J. Hermsen, Paleontological Research Institution, Ithaca, NY, USA; Maria A. Gandolfo, H. Bailey Hortorium, Plant Biology Section, School of Integrative Plant Sciences, Cornell University, Ithaca, NY, USA

*judn@william.jewell.edu

Azolla is a small group of ferns with a long history. There are 6-7 living species of these minute aquatic plants, but there are many fossil species from Upper Cretaceous and Cenozoic deposits worldwide. While most fossil species are represented only by spores, at least eleven extinct species have been described based on sporophytes and associated or in situ spores. Therefore, Azolla is a good candidate for investigating the importance of the fossil record in phylogeny reconstruction. Phylogenetic analyses of DNA sequence data from extant species have consistently found support for the hypothesis that extant Azolla comprise two sister clades, section Azolla (comprising A. caroliniana, A. filiculoides, A. mexicana, A. microphylla, and A. rubra), and section Rhizosperma (including A. nilotica and A. pinnata). Section Azolla is characterized by megaspores with three floats and anchor-tipped glochidia (hairs) on the microspore massulae, whereas section Rhizosperma has nine-floated megaspores and microspore massulae with simple or no glochidia. Alternatively, Saunders and Fowler (1993) suggested that A. nilotica may be sister to all other extant Azolla. We investigated the phylogeny of Azolla using morphology from both living and fossil species. We constructed a matrix of six living and seven extinct species, with the extant Salvina cucullata as the outgroup; all fossil species are represented by both sporophytes and spores. We developed a matrix of 33 characters and used a Bayesian tip-dating approach implemented in MrBayes 3.2.7. In this analysis, Markov chain Monte Carlo (MCMC) analyses were used to estimate the phylogeny based on the morphological character matrix, a likelihood model of morphological evolution, the ages of the fossil taxa, and a set of prior probabilities on model parameters. The results of our analyses support a model of relationships in which Azolla nilotica and A. pinnata are not part of a monophyletic group sister to a clade that includes the remaining extant species; rather, A. nilotica is sister to all other extant species. This result contrasts with the results of previous analyses based on DNA sequences from extant species only and suggests that the evolution of spore characters in Azolla is complex.

Linear interactions or non-linear abstractions: Do climate and tectonics predictably affect Cenozoic ecosystems?

Tyler Kukla*, Department of Geological Sciences, Stanford University; C Page Chamberlain, Department of Geological Sciences Stanford University

*tykukla@stanford.edu

Simplicity often correlates with scale. Basic physics does well to explain atmospheric circulation on the largest (planetary) and smallest (a finite parcel of air) scales, but somewhere in between we find turbulence–a problem so hard that many joke it is pondered by omniscient deities. Ecosystems, characterized by complex networks and vast unseen interactions, sometimes feel like biology’s “turbulence”, especially when trying to predict their response to change. Some work supports the notion that ecosystem change is not a single function of the forcing while others find evidence for more universal, deterministic links between ecology and climate. These growing bodies of literature are not necessarily in conflict, but they beg the question of on what scales and under what conditions might we find emergent order in ecological complexity.

As with physical models of atmospheric circulation, defining simple relationships between climate, landscapes, and ecosystems may be a matter of scale. The geologic past provides a large-scale approach to external forcing (i.e. building a mountain belt or glaciating an ice-free world) and ample time for adaptation.

Here, I present cases from the Holocene and Paleogene that support a deterministic relationship between climate or tectonic forcing and the ecosystem (particularly vegetation) response. This work implies that simple relationships exist at large scales (at least sometimes). But these case studies pose more questions than they answer. The role of complexity in climate-driven ecosystem change and the timescales at which these paleo-lessons are applicable is unclear and ripe for discussion.

Exceptional greening of mid-latitude ecosystems during Cenozoic warm intervals

*Jeremy.Rugenstein@colostate.edu

Ancient Forests and Modern Conservation: a Living Australian Gondwana Fossil Heritage at Risk

Robert M. Kooyman, Department of Biological Sciences, Macquarie University, Sydney, Australia; Peter Wilf*, Department of Geosciences, Pennsylvania State University, University Park, PA, USA

*pwilf@psu.edu

Recent wildfires affected about a third of the area of the World Heritage Gondwana Rainforests of eastern Australia and exposed the vulnerability of a rich repository of diversity, endemism, and global living-fossil heritage to rapid extirpation and extinction. The living rainforests of Australia protect more than 40 myr of globally significant rainforest evolutionary history, but despite World Heritage status, they have not received commensurate, effective conservation and protection. In severe drought conditions, and with warming weather, lightning strikes started forest fires in October to November 2019, and these quickly spread into forest areas that rarely burn, and into rainforests that never burn. The paleo-Antarctic rainforest lineages (PARLs) these rainforests harbor are living plant taxa with fossil records in the mid-high latitude paleorainforests of the Cretaceous and Paleogene Southern Hemisphere that survived in Australia. The Miocene intensification of drying in Australia saw the retreat of PARLs to the few remaining, geographically restricted and still shrinking wet places. The PARLs co-occur in these locations in assemblages reminiscent of those represented in fossil assemblages in Patagonia, Antarctica, and Australia. As one example, the cool wet, upland forest assemblages of the Border Ranges and Nightcap Range in New South Wales includes species in Dicksonia (Dicksoniaceae), Todea (Osmundaceae), Araucaria (Araucariaceae), Callitris (Cupressaceae), Nothofagus (Nothofagaceae), Akania (Akaniaceae), Doryphora and Daphnandra (Atherospermataceae), Ceratopetalum and Caldcluvia (Cunoniaceae), Elaeocarpus and Sloanea (Elaeocarpaceae), Wilkiea (Monimiaceae), Syzygium (Myrtaceae), Quintinia (Paracryphiaceae), Orites (Proteaceae), Austrobuxus (Picrodendraceae), Symplocos (Symplocaceae), and Ripogonum (Ripogonaceae). What the fires exposed was the vulnerability of these forests and many ancient Gondwanan lineages to rapid extinction. What is now apparent is that protecting these forests is a modern conservation challenge that needs to be informed by evolutionary history, paleobotany, and the current day distribution of the living fossil lineages.

Phylogenetic models should not ignore paleobiome structure when inferring ancestral biome affinities

Michael Landis*, Department of Biology, Washington University in St. Louis, St. Louis, MO, USA; Erika Edwards, Department of Ecology & Evolutionary Biology, Yale University, New Haven, CT, USA; Michael Donoghue, Department of Ecology & Evolutionary Biology, Yale University, New Haven, CT, USA

*michael.landis@wustl.edu

The paleobotanical record provides invaluable evidence regarding the regional climates and habitats of Earth's past, but statistical phylogenetic models rarely accommodate these data when inferring the ancestral biome affinities of extant lineages. To better understand how lineages shift between biomes in space and time, we developed a phylogenetic biome shift model in which each lineage shifts between biomes and disperses between regions at rates that depend on the lineage’s biome affinity and location relative to the spatiotemporal distribution of biomes at any given time. To study the behavior of the biome shift model in an empirical setting, we developed a literature-based representation of paleobiome structure for three mesic forest biomes, six regions, and eight time strata, ranging from the Late Cretaceous (100 Ma) through the present. We then fitted the model to a time-calibrated phylogeny of 119 Viburnum species to compare how the results responded to various realistic or unrealistic assumptions about paleobiome structure. Ancestral biome estimates that account for paleobiome dynamics reconstructed a warm temperate (or tropical) origin of Viburnum, which is consistent with our previous fossil-based estimates of ancestral biomes. In Viburnum, imposing unrealistic paleobiome distributions led to ancestral biome estimates that eliminated support for tropical origins, and instead inflated support for cold temperate ancestry during the warmer Paleocene and Eocene. The biome shift model we describe is applicable to the study of evolutionary systems beyond Viburnum, and the core mechanisms of our model are extensible to the design of richer phylogenetic models of historical biogeography and/or lineage diversification. We conclude that biome shift models that account for dynamic geographical opportunities are important for inferring ancestral biomes that are compatible with our understanding of Earth history.

Enhancing the Utility of Phytoliths for Understanding the Evolution and Paleoecology of the Arecaceae

Samuel Lavin*, Department of Biology, University of Washington, Seattle, WA, USA; Bailey Armos, Department of Biology, University of Washington, Seattle, WA, USA;; Shannon Khem, Department of Biology, University of Washington, Seattle, WA, USA; Dylan Hart, Department of Biology, University of Washington, Seattle, WA, USA; William Brightly, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Camilla Crifò, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Alex Lowe, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Alice Novello, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA / CEREGE, Technopôle Environnement Arbois-Méditerrannée, Aix-en-Provence, France; Elena Stiles, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Paige Wilson, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Timothy J. Gallaher, University of Washington Department of Biology and Burke Museum of Natural History, Seattle WA, USA / Bishop Museum, Honolulu, HI, USA; Caroline A. E. Strömberg, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA.

*stlavin@uw.edu

Ever since they first appeared during the Late Cretaceous, members of the palm family (Arecaceae) have been ubiquitous in the fossil record. Traditionally, palms have been considered a key indicator of warm climates. In addition to leaf macrofossils, fruit, and pollen, palm phytoliths have gained utility as paleoecological indicators. Phytoliths are microscopic silica bodies accumulated in the tissues of many plants. Different plant taxa have unique phytolith morphologies, making them useful diagnostic tools. However, palm phytoliths currently lack diagnostic resolution below the family level, limiting our ability to fully utilize these powerful tools. The goal of our project was to increase this resolution by analyzing the morphology of phytoliths from across the entire Arecaceae family in more detail than has been possible before. We used confocal microscopy to take sharp, high-resolution images of palm phytoliths. Using these images, we took several key measurements, to which we applied multivariate ordination methods. Our analysis allowed us to test how well we can differentiate palm subclades within Arecaceae based on phytolith morphology. Ultimately, we hope to use this information to determine when and where specific clades of palms appeared in the fossil record, increasing our understanding of the evolution of the palm family. This will also allow us to describe past environments in more detail based on palm phytoliths, including estimating more specific climate parameter ranges, and characterizing particular biomes and habitats.

Floral elements from the Late Campanian Jose Creek flora, McRae Formation (74.6 Mya), New Mexico

Jaemin Lee*, Dept. of Integrative Biology & Museum of Paleontology, University of California, Berkeley; Dori L. Contreras, Perot Museum of Nature and Science, Dallas; Garland R. Upchurch, Texas State University at San Marcos; Cindy V. Looy, Dept. of Integrative Biology, Museum of Paleontology & University and Jepson Herbaria, University of California, Berkeley.

*jaeminlee0622@berkeley.edu

We present new floral elements from the Late Campanian Jose Creek Member, McRae Formation from south-central New Mexico. The specimens come from a 1.2km long bed of recrystallized volcanic ash (U-Pb dated ~74.6 Ma) that preserves a rich compression/impression flora representing a megathermal forest. Based on leaf megafossils, the flora is one of the most diverse single-deposit Cretaceous floras described to date, and quantitative censuses show that angiosperms are the most dominant group across the landscape (74% of leaf specimens, 83% of coverage). Among the reproductive remains, four types of isolated flower and four inflorescence/infructescence morphotypes are recognized thus far. These floral elements are preserved as compression/impressions and lack anatomical details, however some of these types are represented by specimens in different developmental stages. Establishing the botanical affinity of these specimens is challenging due to poor preservation of androecium and gynoecium in most morphotypes. Here we describe the diversity of floral morphotypes from the deposit.

Functional diversity, transference of function, and complexity in vascular plant reproductive structures

Andrew B. Leslie*, Geological Sciences Department, Stanford University, Stanford, CA, USA; Luke Mander, The Open University, Milton Keynes, United Kingdom

*aleslieb@stanford.edu

Plant reproductive structures have increased in maximum complexity through time, evolving from the simple sporangia of Silurian taxa to the intricate contraptions of orchids and passionflowers. On a general level, this increase probably reflects greater functional demands on reproductive structures in some lineages, combined with specialization in how these demands are met. But understanding when and how complexity has changed through time, and how that may relate to differences in reproductive function, is challenging because lineages produce disparate reproductive structures that are difficult to compare. We quantify changes in reproductive complexity across plants using two simple aspects that can be applied to any lineage: the total number of parts present in a given structure and how many times these structures are repeated. We score fossil and living genera for eleven characters that tally the sterile and fertile components in reproductive structures and record the degree to which these components are clustered, and we then ask how the number and arrangement of parts has changed over time and across lineages with different reproductive biology and functional demands. We find a rapid rise in complexity to the Pennsylvanian, as many lineages evolved a basic set of structures to support and protect sporangia, followed by a more gradual rise in complexity over the Mesozoic associated with diversification in seed plants, particularly with regards to structures related to pollination syndromes and ovule enclosure. In both seed plants and pteridophytes, reproductive structures that perform more reproductive functional roles tend to have a greater number of parts and a greater number of unique part combinations. These results suggest that shifting the performance of reproductive functions away from sporangia is one of the primary patterns in plant reproductive macroevolution, and the extent to which this process occurs generates the patterns of morphological complexity and disparity that we see across plant lineages.

Plant community and climatic response to middle Miocene environmental change in the Pacific Northwest (USA)

Alex Lowe*, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Caroline A. E. Strömberg, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; William Rember, Department of Geological Sciences, University of Idaho, Moscow, ID, USA ; Thomas Dillhoff, Burke Museum, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Richard Dillhoff, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Margret Steinthorsdottir, Swedish Museum of Natural History, Stockholm, Sweden; Mark Schmitz, Department of Geoscience, Boise State University, Boise, ID, USA

*loweaj01@uw.edu

The US Pacific Northwest (PNW), including Washington, Oregon, and Idaho, hosts an extensive suite of Oligocene–Miocene fossil plant sites, spanning in time across several pronounced environmental perturbations. The Middle Miocene Climatic Optimum (MMCO) was a period of elevated global temperatures, from ca. 17 to 14 Ma, terminated by a cooling trend, termed the Middle Miocene Climatic Transition (MMCT). In addition, Earth’s most recent continental flood basalts, the Columbia River Basalts (CRBs), erupted ~95% of its volume in the Pacific Northwest from 16.7 to 15.9 Ma. This collaborative study focuses on 18 PNW fossil sites spanning ca. 32 to 10 Ma, many of which have extensive pre-existing macrofossil collections, studied by paleobotanists such as Chaney, Axelrod, and Wolfe. In re-visiting these earlier works, we will radiometrically date interbedded ashes at these sites to establish a high-resolution temporal framework, using U-Pb CA-ID-TIMS methods which can produce ±20 ka resolution. Within this framework, we plan to: 1) better document the regional manifestation of climate change in the PNW during the MMCO and MMCT using paleobotany-based paleoclimate proxies, 2) provide an integrated perspective on the response of plant communities to these middle Miocene environmental changes by combining macrofossil, palynomorph, and phytolith evidence, and 3) shed light on the CRBs’ potential role in MMCO warming by producing CO₂ estimates from fossil leaf cuticle. This project will provide a comprehensive and vital example of long-term regional responses to global climatic change and regional volcanism.

Reconstructing spatio-temporal patterns of vegetation change in the Permian of Gondwana: a model-based palynological approach

Cindy Looy*, Department of Integrative Biology, University of California, Berkeley, UC Museum of Paleontology, University and Jepson Herbaria, Berkeley, CA; Ivo Duijnstee, Department of Integrative Biology, University of California, Berkeley, UC Museum of Paleontology, Berkeley, CA

*looy@berkeley.edu

We recently described three new voltzian conifer taxa from the middle Permian South Ash Pasture flora, Texas, based on morphological characteristics of ovuliferous cones (Pseudovoltzia sapflorensis), isolated dwarf shoots (Wantus acaulis) and numerous broad, parallel-veined leaves (Johniphyllum multinerve). The discovery of these conifers is significant for five reasons. (1) The ovuliferous P. sapflorensis cones are the earliest members of this genus in western Euramerica. (2) The broad, parallel-veined leaves of J. multinerve have a macro-morphology that was thus far not known from Paleozoic conifers, but well known from other taxa–including Cordaites. Similar-shaped leaves from early to middle Permian compression floras may thus have been routinely misidentified in the past as non-coniferous. (3) The macro-morphology of J. multinerve leaves resemble younger Mesozoic voltzian conifer lineages, however, their epidermal features are comparable with late Permian taxa. (4) All 476 J. multinerve specimens were found as isolated, dispersed leaves. When preserved, their swollen leaf bases suggest that they were actively abscised–a functional trait that is unusual in Paleozoic conifers. (5) With five potential sporophylls and no intermediate sterile scales, the dwarf shoot W. acaulis is unlike those of other late Paleozoic conifers, and may be an early, basal member of a clade that potentially includes Triassic conifers such as Aethophyllum and Telemachus. Interestingly, these Mesozoic taxa also had broad, parallel-veined leaves. Together, the three new taxa increase both the taxonomic diversity and the morphological disparity among reproductive and vegetative structures in late Paleozoic voltzian conifers. Gypsum layers and weakly developed inceptisols recovered from layers above and below the fossiliferous beds suggest that the plants grew on floodplains in a dry climate. These findings once more illustrate that structural evolution, innovation, and diversification in this group of conifers took place in drier environments, where chances of preservation are unlikely.

Ecological disturbances in the latest Permian reflected in palynomorphs from the Dolomites

Hendrik Nowak*, Museum of Nature South Tyrol, Bozen/Bolzano, Italy; Evelyn Kustatscher, Museum of Nature South Tyrol, Bozen/Bolzano, Italy / Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität, München, Germany / Bayerische Staatssammlung für Paläontologie und Geobiologie, München, Germany

*hendrik.nowak@naturmuseum.it

In the Dolomites (Southern Alps; Northern Italy), the Lopingian (late Permian) and Early Triassic are represented without a major hiatus by shallow-marine sediments. The region is consequently of great interest for the study of the end-Permian mass extinction. Palynomorphs from the Dolomites have been studied occasionally in this context as well, but a recent project produced new data from several localities that provide a clearer picture.

A previously mostly overlooked, but important component of the late Permian palynofacies in this region are unidentified organic-walled microfossils of possible algal or fungal origin. In the Laurinswand section (Rosengarten Massif), high abundances of these microfossils coincide with impoverished ostracod faunas indicating a stressed environment. They disappear near the Permian–Triassic boundary.

Also near the boundary, spores and spore tetrads, primarily of lycophytes, occur with a drastically increased frequency. Similar signals have been reported from across the globe. The frequent occurrence of permanent tetrads suggests an ecological disturbance that disrupted the plants’ reproductive abilities. The general increase in spores compared to pollen – a so-called “spore spike” – is considered to indicate the collapse of the gymnosperm-dominated Permian flora, although gymnosperm pollen continue to be present. The demise of the Permian flora has been linked to the mass occurrence of the problematic organic-walled microfossil Reduviasporonites. This mass occurrence has also been used as a marker for the Permian–Triassic boundary. However, we found increases in Reduviasporonites in the Dolomites to occur locally in different stratigraphical positions, in at least one case postdating the “spore spike”.

The Middle Jurassic (Bajocian–Bathonian) Paleoenvironment and Paleoclimate of Hojedk Formation, Tabas Basin, Iran: Paleobotanical and Palynological Investigations

Saeed Maleki-Porazmiani*, Department of Geology, College of Science, University of Tehran, Tehran, Iran

*maleki.saeed@ut.ac.ir

A palynological and paleobotanical study of the Middle Jurassic strata in Tabas Basin (east of Iran) was performed by sampling the Tabas Coal Mine. The Bajocian–Bathonian micro and macroflora in the studied area gave a deeper insight into both the paleoecology and paleoclimate of the northern Neotethys. Abundant spore, pollen grains, and plant fossils yielded significant information on the diversity of the flora. The flora was dominated by ferns (40– 55%), followed by cycadophytes and conifers. Ginkgophytes (10%) were also commonly recorded. Paleobotany and palynology were also used to suggest a paleoenvironment for the basin during the Bajocian–Bathonian age. Lowland, River, Upland, and Coastal Plant EcoGroups (PEGs) were defined based on the studied Macroflora. Occurring miospores were also assigned to Lowland, River, Coastal, and tidally influenced Sporomorph EcoGroups (SEGs). Domination of Lowland group in both SEGs and PEGs model indicates a low land environment during deposition of the Formation. Based on index dinoflagellate cysts, the parental plants of spores and pollen grains, SEGs, and PEGs model a warm paleoclimate estimated for the Tabas Block, located in the northern end of the Neotethys Ocean during the Bajocian-Bathonian.

No bananas but extinct ginger relatives: Fruits and seeds of Zingiberales from the Maastrichtian-Paleocene of India.

Steven R Manchester*, Florida Museum of Natural History, University of Florida, Gainesville FL, USA; Shannon Robinson, Department of Biology, University of Florida, Gainesville FL, USA; Dashrath Kapgate, Department of Botany, J.M. Patel College, Bhandara, India; Rashmi Srivastava, Birbal Sahni Institute of Palaeobotany, Lucknow, Uttar Pradesh, India; John Benedict, Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA ; Selena Y. Smith, Earth and Environmental Sciences, University of Michigan, Ann Arbor MI, USA

*steven@flmnh.ufl.edu

Three extinct genera of Zingiberales are recognized based on fruits and seeds preserved in chert from the Late Cretaceous-early Cenozoic Deccan Intertrappean beds of central India: 1) Fruits and seeds of “Musa”cardiosperma Jain were e-evaluated based polished slices, peels, and micro-CT scanning methods. Newly collected specimens indicate that this species was common and widely distributed across central India during the latest Cretaceous (late Maastrichtian). The operculate seeds with straight, bulbous embryos lack the micropylar collar found in extant Musaceae and have only a weakly defined, oblique chalazal chamber. Although it clearly represents Zingiberales and displays some similarities to bananas, morphological differences indicate this species does not conform to Musaceae. 2) Another new genus, from the Maastrichtian Marai Patan site, has widely obovate operculate seeds, lacking a micropylar collar, that are perfectly rectangular in transverse view with two planes of bisymmetry, contrasting with the irregularly shaped seeds of “M.” cardiosperma. This species has a transversely lensoidal, rather than oblique, chalazal chamber. 3) Callistemonites indica Bande, Mehrotra & Prakash, based on partially permineralized fruits with intact operculate seeds, is from the Paleocene of Ghughua, Mandla, India. This species is distinct from the other two, having smoothly rounded ellipsoidal seeds with uniform seed coat thickness. Seed types 1) and 2) differ from type 3) and from all extant Zingiberales in the presence of massive thickening of seed coat at the hilar region. Together, the three species reveal an interesting diversity of Zingiberales inhabiting the Indian subcontinent when it was nearly equatorial, isolated from other land masses, and experiencing the effects of periodic intense volcanism.

A Paleobotanical Perspective on the Middle to Late Paleocene in Central Wyoming

Anjali, Manoj*, Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA; Alex, Lowe, Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA; Alexis, Licht, Department of Earth and Space Sciences, University of Washington Seattle, WA, USA; Ian, Spendlove, Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA; Megan, Mueller, Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA; Christopher, Beard, Department of Ecology and Evolutionary Biology & Biodiversity Institute, University of Kansas, Lawrence, KA, USA

*anjali04@uw.edu

The Paleocene Eocene Thermal Maximum (PETM), a period of intense warming 56 million years ago, is an important analogue to the present-day climate change but the warming trends and climatic shifts leading up to it have been less studied. Outcrops of the Fort Union Formation in the Bison Basin in south-central Wyoming feature a sequence of well-preserved paleosols, mammalian and floral remains from the middle to late Paleocene (Tiffanian land mammal age, from 62 to 57 million years ago) and provide an excellent opportunity to examine this period. This study focuses on fossil plants --primarily leaves-- collected using a census collection technique from two distinct beds above and below a fossil mammal locality of Tiffanian Ti2 age, approx. 60 million years old. We present pictures and identifications of these two fossil floras. The ancient plant communities are characterized by designating morphotypes and determining their relative abundance and diversity. Our identifications highlight significant differences between both floras but it is unclear if they are related to changes in climate, landscape or both. These results are a preliminary step before using Leaf Margin Analysis and Climate Leaf Analysis Multivariate Program (CLAMP) to document the regional middle Paleocene climate.

Fossil flowers and fruit illuminate the origins of the largest palm tribe

Kelly Matsunaga*, Negaunee Institute for Plant Conservation Science and Action, Chicago Botanic Garden, Glencoe IL, USA; Selena Y. Smith, Earth and Environmental Sciences, University of Michigan, Ann Arbor MI, USA; Steven R. Manchester, Florida Museum of Natural History, University of Florida, Gainesville FL, USA; Sharadkumar Patil, Department of Botany, Bhagwantrao Arts and Science College, Etapalli, Maharashtra, India

*matsunaga@ku.edu

Palms (Arecaceae) are a morphologically diverse and ecologically important monocot family distributed throughout tropical–subtropical regions worldwide. Despite having a rich fossil record that extends into the Late Cretaceous, much remains unknown about the origins of the family and its major lineages. New discoveries are therefore crucial for better understanding the history of these glorious plants. We studied flowers and fruits of a new fossil palm from the Maastrichtian–Danian Deccan Intertrappean Beds of India, which preserves the oldest and only permineralized palm flowers known in the fossil record. The specimens consist of several inflorescence fragments and a single fruit specimen, all originating from the same chert block. The inflorescences bear dense, helically arranged floral triads consisting of a central pistillate flower and the remnants of two lateral (possibly staminate) flowers. The corresponding fruit is obovate, bearing a single seed with a basal embryo. Phylogenetic analyses using a combined molecular and morphological dataset, which samples 178 extant palm genera, place this palm in the crown group of tribe Areceae (subfamily Arecoideae) with very high node support. Today Areceae is the largest palm tribe (61 genera, >600 species) and is distributed throughout the Indo-Pacific region. Within Areceae, many early-diverging clades occur in the Indian Ocean, whereas more nested lineages are distributed in India, the Indo-Australian archipelago, and the Pacific. The presence of Areceae in India 66 million years ago, prior to the collision of India with Eurasia, suggests that an “out-of-India'' migration of at least some members of Areceae into Eurasia is plausible, as has been hypothesized for other groups. While such dispersal routes remain speculative, these fossils nevertheless demonstrate that Areceae has a deep history in the Indian Ocean region and provide essential data for untangling the biogeographic and evolutionary history of palms.

Assessing the effects of shade on sycamore ecophysiology: present and past

Joseph Milligan*, Andrew Flynn, and Daniel J. Peppe, Terrestrial Paleoclimatology Research Group, Department of Geosciences, Baylor University, Waco, TX, USA

*Joseph_Milligan@baylor.edu

Plants are sensitive indicators of the environment and climate in which they live. Leaves are a plant’s primary photosynthetic organ, and thus are very sensitive to changes in light availability. Changes in the light environment of the leaf has important consequences for leaf morphology, anatomy, and physiology. These changes have been used to identify ‘sun’ and ‘shade’ morphotypes of fossil leaf assemblages. While taphonomic processes and degradation may favor the selection of ‘sun’ morphotypes, recent evidence suggests that fossils from are a range of light conditions are preserved in the fossil record. This raises the possibility that ancient light environments can potentially be reconstructed using fossil leaves, particularly if the relationship between light availability and modern leaf traits are quantified. Here we characterize the response of Platanus occidentalis to changes in light quantity and quality using six experimental light conditions: natural light, black shade cloth (30%, 60%, 90%), and green shade cloth (60%, 87%). Leaf size (R2=0.77; P= 0.004), leaf perimeter (R2=0.96; P= 0.006), cell area (R2=0.9; P= 0.001), and cell undulation index (R2=0.96; P= <0.001) all increased with decreasing light quantity. However, light quality did not affect leaf or cell morphology. Using these relationships, we then compare the cell anatomy and δ13C response of modern P. occidentalis to fossil Platanites raynoldsii from the Paleocene rocks (~65.8-62.2 million years ago) of the Nacimiento Formation in the San Juan Basin, New Mexico to assess for evidence of varying light conditions through time. While our preliminary results are qualitative, we are working develop a quantitative proxy for reconstructing light environments, which will make it possible to reconstruct light availability and canopy architecture in the fossil record.

Paleoenvironmental reconstruction of Early Miocene fossil sites from Tinderet (Nyanza Province, Western Kenya) and its implications for hominoid evolution

Daniel J. Peppe*, Terrestrial Paleoclimatology Research Group, Department of Geosciences, Baylor University, Waco, TX, USA; Kennedy Oginga, Terrestrial Paleoclimatology Research Group, Department of Geosciences, Baylor University, Waco, TX, USA; William E. Lukens, Department of Geology and Environmental Sciences, James Madison University, Harrisonburg, VA, USA; James Lutz,Wildland Resources Department, Utah State University, Logan, UT, USA

*daniel_peppe@baylor.edu

Early Miocene fossil sites surrounding Tinderet Volcano in western Kenya document some of the earliest occurrences of the large bodied hominoid Proconsul. The sites are thought to have been deposited contemporaneously between 19 – 20 Ma, but they preserve different primate fossil assemblages. The differences in the primate communities could be due to variations in paleoenvironment or because the sites are different ages. However, paleoenvironmental reconstructions for the sites are generally lacking and there is limited age control, limiting our ability to address this question. Here we report a detailed geological and paleobotanical assessment of three Tinderet fossil primate sites: Koru 16, Koru 21, and Kapurtay New.

Sedimentological and paleosol analyses indicate that all of the sites sample analogous depositional environments with similar types of paleosol development. Qualitative and quantitative analyses of the paleosols indicate periodic landscape disturbance and seasonally available water. Carbon isotopes from soil organic matter indicate the presence of C₃ vegetation similar to modern riparian woodlands and dry deciduous forests. At Koru 16, a widespread stratigraphic unit preserves abundant drab-haloed root traces, fossil leaves, and casts of fossil roots, branches and tree stumps. Reconstructions of the forest structure using the diameter and spatial distribution of stump casts indicates the interval represents a densely wooded patch of young, mature trees with canopy breaks. The reconstructed tree density is similar to present-day tropical forests with large-bodied primate communities. Taken together, our analyses indicate that the paleoenvironment of the three sites was similar and sample a frequently disturbed dry forest landscape within a seasonally dry climate. Thus, we suggest that differences in the hominoid assemblages between the sites is unlikely due to differences in the environment and vegetation structure and instead because the sites sample different intervals of time in the early Miocene.

Quantitative paleobiological methods, customized for the study of plant–insect interactions in the fossil record

Sandra R. Schachat*, Department of Geological Sciences, Stanford University, Stanford, CA, USA; S. Augusta Maccracken, National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA / Department of Entomology, University of Maryland, College Park, MD, USA; Conrad C. Labandeira, National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA / Department of Entomology, University of Maryland, College Park, MD, USA

*schachat@stanford.edu

The discipline of marine invertebrate paleontology has undergone a revolution of methods development during the past few decades, facilitating studies of macroevolution and macroecology that were unimaginable before the advent of desktop computing. However, the study of plant–insect interactions in the fossil record is far younger than the study of fossilized clams and snails: it was barely ten years ago that a taxonomic system (the "Damage Type" system) was introduced to catalog the different types of insect damage on fossil plants. Following the formalization of the Damage Type system, many more fossil floras have been examined for evidence of herbivory; such studies become more popular with each passing year. The new abundance of data on plant–insect interactions in the fossil record raises the question of how we can identify trends in the evolution of plants and their herbivores on multi-million-year timescales.

We have developed novel quantitative techniques to address two fundamental questions. First, how can we know that we've sampled enough leaves from a given assemblage or taxon? And second, how can we standardize our data to generate the most biologically meaningful comparisons of herbivory across different plant assemblages and taxa? In this presentation I will share: novel statistical methods that we developed for the analysis of plant–insect interaction data in the fossil record, guidelines for sampling fossils and analyzing data, new statistical and paleoecological insights gleaned from the use of these methods, and an overview of the most relevant outstanding questions.

Diversification in the Rosales is influenced by dispersal, geographic range size, and pre-existing species richness

Andrew Simpson*, National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA; Scott Wing, National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA; Charles Fenster, Department of Biology and Microbiology, South Dakota State University, Brookings, SD, USA

* andy.g.simpson@gmail.com

Geographic range size, because of its relationship with diversification and extinction, potentially links ecological and evolutionary processes. We use the MuSSE method (Multiple-State Speciation and Extinction) to explore the effects on genus-level diversification of two genus-level traits (geographic range size and within-genus proclivity to speciate, proxied by within-genus species richness), and two individual traits (seed dispersal mechanism and growth habit), using the angiosperm order Rosales as a study group. At the species-level, animal dispersal enhances diversification rate in both woody and herbaceous lineages, while woody lineages without animal dispersal have higher extinction rates than speciation rates. At the genus level, we find herbaceous taxa to have net positive diversification rates regardless of other character states. However, diversification rate variation is also explained by two interactions: (1) a three-way interaction between large geographic range, animal-mediated dispersal, and high within-genus species richness, whereby genera possessing all three traits have high diversification rates, and (2) a four-way interaction by which the three-way interaction is stronger in woody genera than in herbaceous genera. Woody lineages not possessing the three trait states preferentially become extinct. Colonization ability may underlie the interaction between dispersal type and range size and may influence diversification rates by decreasing extinction rates during late Cenozoic (especially Pleistocene) times of climate volatility. Thus, colonization ability could be used to predict future extinction risk to improve conservation success.

Decoding Leaf Characters That Drive Family Level Identification Through Computer Vision

Edward J. Spagnuolo* & Peter, Wilf, Department of Geosciences, Pennsylvania State University, University Park, PA, USA

*edspagnuolo2000@gmail.com

Thousands of species of fossil leaves are incorrectly classified, and many angiosperm families have no established, diagnostic leaf architecture characters. Most machine-learning studies on extant leaves have focused on identification at the species level, but family level identification is critical for paleobotanists because nearly all leaf fossils represent extinct species from extant families. More recent computer vision work has successfully demonstrated that leaf characters conserved within plant families have potential for fossil identification (Wilf, Serre et al. 2016, PNAS), and we here present the first attempt to “translate” novel leaf information from machine outputs into a form useful to human botanists. We analyzed published heat maps of cleared leaves from the 2016 work that display regions of highest importance for family level identification, as determined from Scale Invariant Feature Transform (SIFT) methods. So far, we have analyzed heat maps of Rubiaceae, Fagaceae, Rosaceae, and Fabaceae because these families had high sample size and were identified with high levels of accuracy by the computer vision system. Rubiaceae has a poor macrofossil record, whereas the other three families are well represented as fossils. We developed a scoring system for the regions of highest diagnostic importance, identified as the reddest regions on the heat maps, based on standard leaf-architectural characters. Many machine-identified features appear to be novel and potentially informative for identification. Promising characters for potential family level identification involve the apical margin and the basal secondary and intersecondary veins for Rubiaceae; lower-order venation, the medial margin, and tooth flanks for Fagaceae; apical mucros for Fabaceae; and tooth apices for Rosaceae. Next steps include multivariate ordinations and cluster analyses to determine variation among families and the inclusion of additional families.

Paleocene - Eocene vegetation and early grass ecology in the San Jorge Basin of Argentine Patagonia

Elena Stiles*, Department of Biology and Burke Museum of Natural History, University of Washington, Seattle, WA, USA; Caroline A.E. Strömberg, Department of Biology and Burke Museum of Natural History, Seattle, University of Washington, WA, USA; Georgina Erra, CONICET, , Universidad Nacional de la Plata, La Plata, Argentina; Javier Gelfo, Division of Vertebrate Paleontology, Universidad Nacional de la Plata, La Plata, Argentina; Francisco Goin, Division of Vertebrate Paleontology, Universidad Nacional de la Plata La Plata, Argentina; Matthew J Kohn, Department of Geosciences, Boise State University, Boise, ID, USA; Richard H. Madden, Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, WA; Robin B. Trayler, Department of Life and Environmental Sciences, University of California Merced, Merced, CA, USA; Carolina Acosta Hospitaleche, Division of Vertebrate Paleontology, Universidad Nacional de la Plata, La Plata, Argentina; Nicolaus Bauzá, Universidad Nacional de la Plata La Plata, Argentina; Timothy Gallaher, University of Washington Department of Biology and Burke Museum of Natural History, Seattle WA, USA / Bishop Museum, Honolulu, HI, USA

* estiles@uw.edu

Modern grasses in the family Poaceae exhibit exceptional taxonomic and ecological diversity, with grassland-dominated habitats covering about 40% of Earth’s land surface. Grasslands today occur in a range of temperate to tropical ecosystems, spanning low to high altitudes and wet to arid climates. However, because of the scant fossil record of grasses before the global Oligocene-Miocene spread of grasslands, the ecology of early grasses and their environmental affinities remain poorly understood. To address this gap, we analyze phytolith assemblages extracted from sediment samples collected at the Estancia Las Violetas locality to reconstruct the vegetation of the late Paleocene - early Eocene Rio Chico Group in the San Jorge Basin of Argentine Patagonia. The coastal lowland deposits of the Las Violetas and Las Flores formations of the Rio Chico Group, dated from 57.9±1.1 Ma to <50.6±0.8 Ma, produced phytolith assemblages comprising among the oldest occurrences of grass phytoliths in the fossil record of South America. Preliminary results of phytolith analyses suggest that early grasses in the Paleocene and Eocene of the San Jorge Basin occurred in low abundances in palm and dicot dominated forests. Further analyses of the studied phytolith record will allow us to (1) reconstruct the vegetation and, thus, the ecological context of early grasses, and (2) test for broad floristic changes across the Paleocene - Eocene transition in southern South America, contributing to our understanding of the impact of this period of extreme global warming on terrestrial ecosystems in the Southern Hemisphere.

Plant community change in the Gulf Coastal Plain during the early Paleogene

Jennifer Wagner*, Department of Integrative Biology, University of California Berkeley, and UC Museum of Paleontology, Berkeley, CA, USA

*jenn_wagner@berkeley.edu

During the early Paleogene, the Earth experienced a long-term global temperature increase punctuated by multiple hyperthermal events. The warming resulted in a reduction of the latitudinal temperature gradient, in addition to a global increase in seasonality and drought. Changes in faunal and floral distribution and composition have been well documented in the western part of North America and other regions during this time period. Several studies have supported the hypothesis that a widespread band of thermophilic plant communities existed and expanded into the mid latitudes, consistent with biota tracking climate change. It is not clear how well these floras are connected, and how exactly they responded during these rapid and long-term global warming events. My goal is to gain insight in the response of Eocene Gulf Coastal Plain (GCP) plant communities to these warming events using various leaf physiognomic traits (e.g., DILP, leaf mass per area, leaf margin analysis, leaf area analysis, and leaf area index) and systematic census of several floras. For this, I plan to revisit and collect floras from several well-preserved GCP floras from the Claiborne group in Tennessee and Kentucky, that have been used in taxonomic studies but not in paleoecological analyses. Where possible, I will use cuticular analysis to describe leaf morphotypes and narrow down their botanical affinity.

Cenozoic temperature and precipitation trends from fossil leaf morphology

Christopher K. West*, Department Geological Sciences, University of Saskatchewan, Saskatoon, SK, Canada; Tammo Reichgelt, Department of Geosciences, University of Connecticut, Storrs, CT, USA

*christopher.west@usask.ca

Half a century of collecting fossil leaf assemblages has led to a wealth of fossil leaf morphological data, from all continents, including Antarctica. The physical environment (light regime, potential for moisture loss, and freezing potential) determines leaf phenotypes. Although not all leaf phenotypic parameters are universal, characteristics such as leaf size and margin architecture, adhere to general trends in, for example, temperature and precipitation. Here, we review Cenozoic terrestrial paleoclimate evolution using a dataset comprising ~200 previously collected fossil leaf assemblages. We subject this dataset to the three most commonly used fossil flora-based paleoclimate proxies: Leaf Margin Analysis, Leaf Area Analysis, and CLAMP, using region-specific calibration datasets. Initial results show the Southern Hemisphere mid-latitudes appear to follow expected global temperature trends, with highest temperatures in the early/middle Eocene, Oligocene cooling, early Miocene warming, and subsequent late Miocene cooling. However, this pattern is absent in the Northern Hemisphere mid-latitudes, as the early Eocene appears relatively cool, with highest temperatures in the middle Eocene, followed by decreasing temperatures until the late Miocene. Climates similar to modern tropical montane everwet biomes appear to dominate in the Northern Hemisphere mid-latitudes in the early to middle Eocene, making way for cooler, drier, and more seasonal conditions in the late Eocene and beyond. The Southern Hemisphere follows a different climate evolution, where warmer global conditions appear associated with subtropical climates, with pronounced temperature and precipitation seasonality, and cooler climates are associated with higher rainfall and less seasonality. High temperature extremes in the tropics during the early Eocene may indicate greater seasonality than modern, which is absent following the middle/late Eocene transition. Preliminary results demonstrate the potential of evaluating global climate from leaf physiognomy, which may greatly improve our knowledge of Cenozoic biome evolution, and highlights the non-uniform response of climates to global temperature evolution.

A Diverse Assemblage of Late Eocene Woods from Oregon

Elisabeth A Wheeler*, North Carolina State University, Raleigh, NC, USA; Steven R. Manchester, Florida Museum of Natural History, University of Florida, Gainesville, FL, USA

*xylem@ncsu.edu

Central Oregon is home to a sequence of Middle Eocene to Early Oligocene terrestrial sediments that contain abundant and diverse fossil woods, fruits and seeds, and vertebrates. Recently, we have been studying anatomically preserved silicified woods from Late Eocene localities near Post, Oregon, in the Crooked River Basin, which have a minimum estimated age of 36.2 MA. These assemblages are less diverse than the Middle Eocene Clarno Nut Beds, Oregon, and have a different composition. At UF locality 279, we have found woods with anatomy similar to extant genera: Pistacia (Anacardiaceae); Celtis (Cannabaceae), Cercidiphyllum (Cercidiphyllaceae), Fagus and Quercus of the red oak group (Fagaceae), and Acer (Sapindaceae), Ulmus (Ulmaceae). To the best of our knowledge, the Pistacia and Celtis woods are the oldest occurrences of woods with characteristics unique to these genera. Other woods can be identified to family, but have a combination of features found in more than one extant genus of that family: Lithocarpoxylon, resembling Lithocarpus, Notholithocarpus, and the evergreen Quercus species (Fagaceae); Hamamelidoxylon, most similar to Sinowilsonia (Hamamelidaceae); and Pterocaryoxylon, with features shared with Juglans (butternut group) and Pterocarya (Juglandaceae). Two genera are likely extinct because they can be identified to family, but have a combination of features that does not conform to any modern genus: Wataria (Malvaceae) which also occurs in Japan, and Platanoxylon (Platanaceae), one of the most commonly occurring fossil woods in the Paleogene of the Northern Hemisphere. Additionally, there are at least four other wood types whose relationships to extant woody plants are unknown. Overall, the traits of this assemblage differ from the older Nut Beds assemblage; all Post woods have distinct growth ring boundaries, whereas one-third of the Nut Beds have indistinct growth ring boundaries. Moreover, two of the Post woods are distinctly ring-porous, a trait not seen in any of the Nut Beds woods; ring-porosity is correlated with the deciduous habit and distinct seasonality. The comparison of the Post assemblages to the Clarno Nut Bed assemblage highlights the middle to late Eocene climate change in central Oregon.

Plant community change in the latest Cretaceous of northeastern Montana

Paige Wilson*, Department of Earth and Space Sciences University of Washington, Seattle, WA, USA; Caroline A.E. Strömberg, Department of Biology and Burke Museum of Natural History, Seattle, University of Washington, WA, USA; Gregory, Wilson, Department of Biology and Burke Museum of Natural History, Seattle, University of Washington, WA, USA

*wilsonp2@uw.edu

The Cretaceous-Paleogene (K/Pg) boundary marks a major mass extinction resulting in global faunal turnover, notably the extinction of non-avian dinosaurs. The Hell Creek Formation in northeastern Montana contains some of the most well-studied vertebrate localities recording this mass extinction, however, very little is known of the floral record in this area. As part of an effort to reconstruct floral changes across the K/Pg in northeastern Montana, this study presents a sequence of latest Cretaceous macrofloral assemblages leading up to the K/Pg boundary. Four plant macrofossil localities from Garfield County, Montana are described and placed in a tight chronostratigraphic framework spanning approximately 1.5 m.y. prior to the K/Pg boundary. Each site preserves leaves and reproductive structures (e.g. cones and seeds), as well as stems and other vegetative structures. These fossils are preserved in siltstone and sandstone lithologies, interpreted as riparian depositional environments. Preliminary analyses indicate that many of these assemblages have taxa in common (e.g., Metasequoia occidentalis, Glyptostrobus europaeus, and “Dryophyllum” subfalcatum), but overall preserve distinct plant communities. This pattern suggests some amount of turnover in forest composition leading up to the K/Pg boundary. In comparing this series of assemblages with the well-studied Williston Basin macrofloral sequence in North Dakota, we find that many common taxa (e.g., Metasequoia occidentalis, “Dryophyllum” subfalcatum, Leeierceia preartocarpoides) are shared across both study regions, but also note differences in floral composition through time. In particular, many angiosperm taxa recovered from our Montana sites appear to be unique, pointing to geographic heterogeneity in forest make-up. This record of plant communities leading up to the K/Pg boundary lends insight into the dynamics of Late Cretaceous ecosystems, trends in vegetation structure leading up to the K/Pg mass extinction, and variations between local and regional floras of the northern Great Plains region.

Abstracts Virtual MPC

POSTER PRESENTATIONS IN ALPHABETICAL ORDER