Smoothness analyses of trace fossils: expanding quantitative toolkits to unravel bilaterian movement ecology during the Ediacaran–Cambrian transition
Bibliographic record
Abstract
Trace fossils provide unique insights into early animal evolution during the Ediacaran-Cambrian transition. Throughout this critical interval, the smoothness (continuity of derivatives) of combined locomotory and feeding trace fossils (i.e. grazing) significantly increased, potentially indicating diverse evolutionary innovations. We propose several quantitative metrics, including smoothness criteria, minimum normalized radius of curvature and power spectral density, to explore these trace fossils, benchmarked by diverse modern analogues. We classify the trace fossils into unsmooth, regional-smooth and smooth trajectories. A noticeable appearance of regional-smooth and smooth trace fossils among different localities took place around the terminal Ediacaran (since ~545 Ma). Through comparison with extant animals, this period is consistent with the rise to dominance of slender mobile bilaterian eumetazoans with a hydrostatic body, coordinated musculature and long-range sensation to maintain course. The increase of body-length-to-width ratio, and locomotory and navigational capacities of the trace-makers are also quantitatively assessed during metazoan evolutionary radiation. Our results pinpoint the time window for the emergence of ecologically dominant benthic mobile bilaterians in an exponential fashion. We also expand quantitative ichnology, offering new criteria to explore palaeobiological and evolutionary implications of animal-sediment interactions at macroevolutionary scale.
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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 | 0.003 | 0.014 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.006 | 0.005 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.003 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".