VIRGIANID BRACHIOPODS OF THE MICHIGAN BASIN, AND ITS IMPLICATIONS FOR POST-EXTINCTION DIVERSIFICATION OF THE SILURIAN PENTAMERIDE FAUNA IN LAURENTIA
Bibliographic record
Abstract
Three virgianid genera are present in the Michigan Basin. The oldest, Virgiana mayvillensis Savage from the Mayville Dolomite, is upper Rhuddanian in age and coeval with the same species on Anticosti Island in eastern Canada. “Virgiana” major Savage, 1916, from the uppermost Lime Island (uppermost Rhuddanian), has an incipient cruralium supported anteriorly by a low median ridge, for which Virgianoides gen. nov. is proposed in this study. Platymerella in the Elwood Formation (uppermost Rhuddanian) was the most southerly virgianid occurrence in the American mid-continent. The early evolution of the Brevilamnulella-Viridita-Virgiana lineage was represented by the early-middle Rhuddanian fossil record of Anticosti Island. Available fossil data indicate that the Virgiana invasion into intracratonic basins did not begin until late Rhuddanian time, represented by the excellent record of V. mayvillensis in the Michigan Basin, and V. decussata in the Hudson Bay and Williston basins. Despite its late arrival, virgianids thrived for a somewhat longer geological time in the Michigan Basin, represented by Virgianoides and Platymerella in the latest Rhuddanian, when virgianids largely became extinct in other basins of Laurentia.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.002 | 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".