Community hydrodynamics created ecological opportunity in Ediacaran shallow marine ecosystems
Bibliographic record
Abstract
The "second wave" of Ediacaran evolution (∼558-548 Ma) was characterized by the appearance of macroscopic organisms in shallow marine settings, where they formed communities with high morphological and ecological diversity, including new and more complex modes of life. Based on analogy with modern marine ecosystems, these early shallow water communities could have substantially modified local hydrodynamic conditions and influenced resource availability, but we know very little about how they interacted with their fluid environment at larger spatial scales. Here, we use computational fluid dynamics to investigate the hydrodynamics of different shallow marine Ediacaran communities based on fossil surfaces from Russia and South Australia. Our results reveal considerable hydrodynamic variability among these communities, ranging from unobstructed flow, to enhanced mixing, to very low in-canopy flow. This variability represents a noticeable shift from the more conserved hydrodynamic conditions reconstructed for older Ediacaran communities from deep water settings. The variation in how shallow marine Ediacaran communities affected local hydrodynamics could have given rise to notable differences in the distribution of crucial water-borne resources such as organic carbon and oxygen. We therefore hypothesize that increasing variability in community hydrodynamics was an important source of habitat heterogeneity during the late Ediacaran. On long timescales, this heterogeneity may have helped sculpt ecological opportunity, fostering the radiation of animals.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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) | 0.001 | 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".