Advancing the plant fossil record across the Permo-Triassic boundary with a focus on phytoliths

The end-Permian mass extinction (~252 Ma ago) drastically altered ecosystems worldwide, not just in the oceans, but also on land. The effects were so profound that it was not until 4-5 million years into the Triassic that the ecosystem of what was then the eastern part of equatorial Pangea, showed signs of recovery. The flora responsible for this recovery appears to have invaded European habitats after their Early Triassic origination elsewhere. Hitherto, no direct evidence exists of where the refugional source areas of the immigrants could have been located. Here, we suggest that North America could be a potential source area for European Triassic conifers. This body of work aims to advance the plant fossil record across the Permo-Triassic boundary in this geographical region. The first part of chapter one focusses on our current understanding of the potential causes of the end-Permian biotic crisis. While there may be a singular cause that set off a cascade of events, the intricate nature of the Earth’s system makes it difficult to identify the specific drivers behind the ecosystem collapse. It appears that many factors have contributed to some degree to the biotic crisis. The second part of this chapter is focused on the effects the biotic crisis had on life on land, particularly on plants and the data that we have available to study these extinction patterns. Analysis of the data that is currently available through various online databases, suggests that the information is insufficient to adequately study extinction patterns. The second chapter is a literature review of the role of silica in plants. Silica is absorbed by plant roots in the form of monosilicic acid, which originates from the dissolution of crystalline silicate and weathering of biogenic silicates in the soil. Silica absorption, once thought to be a passive process, has been shown to be driven by active transport mechanisms. Depending on where the silica is deposited in the plant, the crystalized shape—the phytolith—may adopt a shape unique to that plant cell or tissue. However, before it crystalizes, the silica plays an important role in the plant’s defense mechanisms. Once crystalized, the opaline silica continues to beneficial; it not only reduces biotic and abiotic stress, it also appears to provide structural benefits.Chapter three examines the Permian and Triassic phytolith record and its potential to support (bio)stratigraphic investigations. In Caprock Canyons State Park and Palo Duro State Park in Texas, the Permian-Triassic boundary is well-preserved and the stratigraphy has been resolved in detail. The phytolith assemblages recovered from the Permian and Triassic strata appear to have limited potential for regional biostratigraphy. However, these phytoliths do form the first evidence of plant life at the western portion of the supercontinent Pangea, a region previously believed to be entirely barren