Middle Cambrian (Drumian) trilobites and agnostid arthropods from the Manuels River Formation, Avalonian New Brunswick: bracketing the green–black facies boundary
Bibliographic record
Abstract
First described by G.F. Matthew 140 years ago, the trilobites and agnostid arthropods of the Manuels River Formation of New Brunswick remain essentially unstudied in modern terms, and most species are known only from his line drawings. Across Avalonian North America, southern Britain, and Belgium, the black mudstone-dominated Manuels River Formation is a distinctive depositional sequence that unconformably overlies greenish mudstone of the Fossil Brook Member of the Chamberlains Brook Formation. This unconformity marks a persistent change from green oxic to black dysoxic marine facies. New collections from limestone nodules at the classic locality at Porter Road yield a low-diversity assemblage dominated by trilobite species of the solenopleurid genera “ Jincella” Šnajdr, 1957 and “ Balticoglaucus” Geyer, 2024. The fauna belongs to the upper Paradoxides abenacus Zone, and associated species of such agnostid arthropods as Goniagnostus Howell, 1935 b, “ Tomagnostus” Howell, 1935 b, and “ Onymagnostus” Öpik, 1979 point to a correlation with the traditional Hypagnostus parvifrons Zone of the Drumian Stage in Avalonian Wales, and the upper “ Acidusus” atavus Zone of Baltica. This interval likely falls in the upper Mawddachites hicksii to lower Paradoxides davidis trilobite zones of Avalonian Newfoundland and Britain. The fauna provides biostratigraphic constraints on a newly recognized bentonite in southern New Brunswick, and on the Avalonian "green–black" boundary. New species are Hypagnostus porterensis, “ Jincella” arenata, and “ Balticoglaucus” avalonensis. Paradoxides abenacus Matthew, 1886, “ J.” acadica (Whiteaves in Matthew, 1886), H. umbo (Matthew, 1886), and “ Euagnostus” tessella (Matthew, 1886) are revised from type and (or) new material.
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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 | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".