A peritidal Burgess‐Shale‐type fauna from the middle Cambrian of western Canada
Bibliographic record
Abstract
Abstract Burgess‐Shale‐type (BST) faunas have proven critical for mapping the Cambrian assembly of animal‐dominated ecosystems, but have so far only been reported from fully subaqueous deposits. Here we integrate evidence from ichnofossils, sedimentary features, and small carbonaceous fossils (SCFs) from the middle Cambrian (Late Guzhangian, Series 3) Pika Formation of western Jasper National Park, Alberta (Canada) to document a unique BST fauna, occupying a peritidal habitat near the outer margin of a large epicratonic sea. Finely laminated shales with mudcracks and dumbbell‐shaped Arthraria ‐type burrows denote a periodically emergent, dysoxic mudflat setting. This same facies yields SCF priapulids, annelids and wiwaxiids typical of deeper‐marine sediments. Recovery of Cirratuliformia‐like annelid chaetae further identifies the likely source of Arthraria burrows and associated faecal pellets. These findings show that Cambrian marine metazoans, including probable members of crown‐group orders, ranged beyond permanently subaqueous deposits. The expanded palaeoenvironmental range of the BST taxa from the Pika biota denotes remarkably broad ecological tolerances, suggesting the existence of a guild of Cambrian metazoan generalists able to colonize at least transiently subaerial settings. Their occupation of offshore peritidal ecologies may have preluded to more extensive metazoan colonization of high‐energy, siliciclastic marginal marine environments.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".