Diversity, paleobiology and ecology of Organic-walled Microfossils from the Proterozoic of Arctic Canada, and implications for early eukaryotic evolution.
Bibliographic record
Abstract
Understanding the appearance and evolution of Life on our Planet (and elsewhere?) requires multidisciplinary approaches intersecting, notably, biology, geology, chemistry and astronomy. Studies of Earth deep times provide insights on the early hydrosphere, atmosphere and geosphere which influenced the development of the early biosphere. Conversely, the transition from prebiotic chemistry to life and subsequent biological changes (prokaryotic then eukaryotic photosynthesis, rise of eukaryotes, appearance of crown-groups, …) also played a role in modifying our young planet. This study focuses on a fundamental period for the diversification of Life on earth, the Proterozoic, that span from 2500 to 541 Ma. The total diversity of organic-walled microfossils present in two unmetamorphosed sedimentary successions from the northwestern Canada was investigated: The Dismal Lakes Group and the lower Shaler Supergroup. These successions represent more than 700 million years of earth history (from 1600 to 900 Ma) and preserve beautiful and abundant microfossils, especially numerous taxa of eukaryotes. This thesis demonstrates that the major diversification of eukaryotes observed in the fossil record at ~800 Ma has, in fact, started earlier and was more gradual. Eukaryotes were diversified by the early Mesoproterozoic and crown groups might have already appeared by then. New and earlier evidence for eukaryovory permits to suggest that predation was probably a powerful driver of this diversity rise. By combining classical paleontological approaches with spectroscopic and ultrastructural analyses, a new candidate of crown-group eukaryote, Ourasphaira giraldae could be proposed. This microfossil, recognized as an early fungus, provides new insights into crown-group diversification in the Proterozoic but also a new calibration point for molecular clock estimates of early eukaryotic evolution, and in particular of the Opisthokontes. Collectively, these studies show that northwestern Canada is an exceptional window on early eukaryotes evolution.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".