Late Ordovician jaw-bearing polychaetes from Anticosti Island, eastern Canada, and their biogeographic significance
Bibliographic record
Abstract
The Upper Ordovician to lower Silurian shallow marine succession of Anticosti Island, eastern Canada, provides one of the most complete records across the Hirnantian in the world. This study reports a diverse assemblage of scolecodonts (polychaete jaws) from the upper Katian and Hirnantian Vauréal, Ellis Bay, and basal Becscie formations of western Anticosti. The collection of 10 samples includes ca. 30 species representing 10 families. The fauna is dominated by polychaetaspids, mochtyellids, paulinitids, and polychaeturids. The family Xanioprionidae and genera Pistoprion, Tetraprion, and Rakvereprion are documented for the first time from the Ordovician of Laurentia. The Anticosti polychaete fauna shows great similarity to the contemporaneous faunas of Baltoscandia. This is evidenced by a high relative abundance of mochtyellids and polychaeturids and a number of common species, thus suggesting that the closing Iapetus Ocean at that time did not constitute a barrier for the dispersal of jaw-bearing polychaetes. Some Laurentian influence is, however, indicated by the occurrence of hadoprionids. Distinct Katian Vauréal and Hirnantian Ellis Bay scolecodonts are likely reflecting faunal reorganization linked to local environmental changes rather than the initial phase of the Hirnantian mass extinction.
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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 | 0.003 |
| Science and technology studies | 0.002 | 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) | 0.001 | 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".