A5022102862- Plant Diversity and Evolution
- Geology and Paleoclimatology Research
- Paleontology and Stratigraphy of Fossils
- Plant and Fungal Species Descriptions
- Plant and animal studies
- Botany, Ecology, and Taxonomy Studies
- Fern and Epiphyte Biology
- Botanical Research and Applications
- Hydrocarbon exploration and reservoir analysis
- Methane Hydrates and Related Phenomena
- Geological and Geochemical Analysis
- Plant Parasitism and Resistance
- Mycorrhizal Fungi and Plant Interactions
- Plant Pathogens and Fungal Diseases
- Geological formations and processes
- Plant Water Relations and Carbon Dynamics
- Mediterranean and Iberian flora and fauna
- Ecology and Vegetation Dynamics Studies
- Atmospheric and Environmental Gas Dynamics
- Climate variability and models
- Photosynthetic Processes and Mechanisms
- Geochemistry and Geologic Mapping
- Geological and Geophysical Studies
- Geological Studies and Exploration
- Evolution and Paleontology Studies
Museum of Boulder
2021-2023
Texas State University
2011-2021
University of Sheffield
2002
Pennsylvania State University
2002
NSF National Center for Atmospheric Research
1990-1991
Denver Federal Center
1987-1989
United States Department of the Interior
1989
United States Geological Survey
1986-1987
Field Museum of Natural History
1987
Theodore Roosevelt High School
1987
The flowering plants that dominate modern vegetation possess leaf gas exchange potentials far exceed those of all other living or extinct plants. great divide in maximal ability to CO 2 for water between leaves nonangiosperms and angiosperms forms the mechanistic foundation speculation about how drove sweeping ecological biogeochemical change during Cretaceous. However, there is no empirical evidence evolved highly photosynthetically active Using vein density ( D V ) measurements fossil...
Abstract. Past warm periods provide an opportunity to evaluate climate models under extreme forcing scenarios, in particular high ( > 800 ppmv) atmospheric CO2 concentrations. Although a post hoc intercomparison of Eocene ∼ 50 Ma) model simulations and geological data has been carried out previously, past high-CO2 have never evaluated consistent framework. Here, we present experimental design for three within the early latest Paleocene (the EECO, PETM, pre-PETM). Together with CMIP6...
The end-Cretaceous mass extinctions, 65 million years ago, profoundly influenced the course of biotic evolution. These extinctions coincided with a major extraterrestrial impact event and massive volcanism in India. Determining relative importance each as driver environmental change across Cretaceous-Tertiary boundary (KTB) crucially depends on constraining CO 2 injected into atmospheric carbon reservoir. Using inverse relationship between stomatal index land plant leaves, we reconstruct...
Analyses of leaf megafossil and dispersed cuticle assemblages indicate that major ecologic disruption high rates extinction occurred in plant communities at the Cretaceous-Tertiary boundary Raton Basin. In diversity increase, early Paleocene vegetational sequence mimics normal short-term succession, but on a far longer time scale. No difference can be detected between latest Cretaceous temperatures, precipitation markedly increased boundary. Higher survival rate deciduous versus evergreen...
Studies of angiosperm leaf cuticles from the Lower Cretaceous Potomac Group reinforce previous evidence for a adaptive radiation flowering plants and suggest unsuspected trends in evolution stomata trichomes.Early (Zone I Brenner or Aptian?) show little interspecific structural diversity, particularly stomatal organization.All species conform to same highly plastic pattern variation subsidiary cell arrangement, which on single several types, including paracytic, hemiparacytic, anomocytic,...
Drewria potomacensis gen. et sp. nov. from the Lower Cretaceous Potomac Group of Virginia (Zone I, probably Aptian) provides first definite Mesozoic megafossil record Gnetales. The stems are slender, display no evidence secondary growth, and show axillary monopodial branching. Attached leaves opposite decussate, borne at swollen nodes, have clasping sheathing bases. Each leaf is oblong, up to 20 mm long, has a dense network longitudinally aligned subepidermal fibers. Leaf venation consists...
Research Article| August 01, 2015 Latitudinal temperature gradients and high-latitude temperatures during the latest Cretaceous: Congruence of geologic data climate models Garland R. Upchurch, Jr; Jr * 1Department Biology, Texas State University, 601 University Drive, San Marcos, 78666, USA *E-mails: gu01@txstate.edu; cscotese@gmail.com. Search for other works by this author on: GSW Google Scholar Jeffrey Kiehl; Kiehl 2Climate Change Research, Climate Global Dynamics Division, National...
The photosynthetic gas exchange capacities of early angiosperms remain enigmatic. Nevertheless, many hypotheses about the causes angiosperm success and how influenced Mesozoic ecosystem function hinge on understanding maximum capacity for metabolism. We applied structure-functional analyses leaf veins stomatal pore geometry to determine hydraulic diffusive Early Cretaceous fossil leaves. All late Aptian—early Albian measured possessed low vein density maximal area, indicating in comparison...
The fossil record demonstrates that mass extinction across the Cretaceous–Tertiary (K–T) boundary is more severe in marine than terrestrial realm. We hypothesize ecosystems were able to recover faster their counterparts. To test this hypothesis, we measured sedimentary δ 13 C as a tracer for global carbon cycle changes and compared it with palaeovegetational reconstructed from palynomorphs cuticles K–T at Sugarite, New Mexico, USA. Different patterns of perturbation timescales recovery...
Terrestrial leaf fossils often form through authigenic preservation in which the surface is coated by a variety of minerals, especially iron oxides. The mechanism this fossilization unclear, because largely hydrophobic surfaces do not readily bind metal ions. Previously proposed mechanisms for mineral encrustation include precipitation minerals sediment pore space and oxides at decay-produced CO 2 . Here we demonstrate that diverse bacterial species rapidly colonize biofilm within days...
Forest vegetation has the ability to warm Recent climate by its effects on albedo and atmospheric water vapour, but role of in warming climates geologic past is poorly understood. This study evaluates forest maintaining Late Cretaceous (1) reconstructing global palaeovegetation for latest (Maastrichtian); (2) modelling under unvegetated conditions different distributions palaeovegetation; (3) comparing model output with a database palaeoclimatic indicators. Simulation Maastrichtian land...
Angiosperm leaf cuticles from the oldest part of Potomac Group reinforce previous paleobotanical evidence for a Cretaceous flowering plant diversification. Dated palynologically as Zone I Brenner (Aptian?), these remains show low structural diversity compared to later and modern angiosperms. All cuticle types conform single plan stomatal construction that is unusual in its extraordinary plasticity: both number subsidiary cells their arrangement vary greatly on epidermis, such stomata might...
Summary The strong positive relationship evident between cell and genome size in both animals plants forms the basis of using stomatal guard cells as a proxy to track changes plant through geological time. We report for first time taxonomic fine‐scale investigation into guard‐cell length use these data infer evolutionary history land plants. Our suggest that many earliest had exceptionally large sizes predicted overall trend increasing within individual lineages is not supported. However,...
In their 1977 study on Potomac Group angiosperms, Hickey and Doyle made only broad comparisons with living taxa. Newer data, especially discoveries of fossil flowers in the coeval deposits increasingly robust molecular phylogenies allow more precise phylogenetic placement fossils. compared most early leaves (Aptian—early Albian) "magnoliids," a paraphyletic group as then defined, but several clades can now be recognized. Leaves dispersed cuticles share epidermal features woody members basal...
Abstract Currently, there is only one paleo‐CO 2 record from plant macrofossils that has sufficient stratigraphic resolution to potentially capture a transient spike related rapid carbon release at the Cretaceous‐Paleogene (K‐Pg) boundary. Unfortunately, associated measurements of stomatal index are off‐calibration, leading qualitative interpretation >2,300‐ppm CO . Here we reevaluate this with proxy based on leaf gas exchange principles. We also test three living species grown 500‐ and...
Abstract We describe in detail the foliar architecture of extant Nelumbo and propose a new genus, Exnelumbites Estrada-Ruiz, Upchurch, Wolfe & Cevallos-Ferriz, for recently discovered leaf macrofossils from Upper Cretaceous (Campanian-Maastrichtian) Olmos Formation Coahuila, Mexico Jose Creek Member McRae south-central New Mexico, U. S. A. The fossils described here consist centrally peltate leaves with 12–13 actinodromous primary veins that terminate broad glandular teeth chloranthoid type....