Trace fossils from the Meishucun section of South China: revisiting ichnotaxonomy, behavioural diversification and ecosystem engineering from a key Ediacaran–Cambrian succession
Bibliographic record
Abstract
Abstract The Ediacaran–Cambrian transition was a time of profound geobiological revolution and sedimentary change in Earth's history, including arguably the most dramatic evolutionary radiation and a remarkable biotic replacement. The complex feedback between diversification of metazoans and their ecological interactions, especially after the extinction of the latest Ediacaran biota, is still debated. Here, we systematically studied the trace fossil content of the Ediacaran–Cambrian succession from the Meishucun section of South China. A total of 20 ichnogenera comprising 31 ichnospecies have been identified in the succession. The occurrence of Treptichnus pedum in the Lower Phosphate of the Zhongyicun Member reinforces the importance of this ichnotaxon as an indicator of the Ediacaran–Cambrian boundary. Our critical review of the trace fossil record of this key succession shows that increases in ichnodiversity, ichnodisparity, degree of bioturbation, and bioturbation depth were accompanied by increases in modes of life and ecosystem engineering throughout the early Cambrian. The dramatic and stepped increased in ichnodiversity and ichnodisparity in the Ediacaran–Cambrian transition, from simple trace fossil morphologies in the Ediacaran to complex branching in the Fortunian, and finally horizontal looping trails and suspension feeding burrows in Cambrian Stage 2, paralleled the shift from the Cambrian information revolution to the agronomic revolution. The dramatic hike in bioturbation intensity and depth that occurred during Cambrian Stage 2 may have resulted in an increase in bioirrigation levels and was conducive to a further deepening of the redox discontinuity surface.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.007 | 0.006 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".