Brachiopods from the Middle Devonian Hamilton Group of Southwestern Ontario, Canada
Bibliographic record
Abstract
The late Middle Devonian (Givetian) Hamilton Group of southwestern Ontario is well known worldwide for its diverse, abundant and well-preserved brachiopod fauna. Yet, despite their undoubted value as a paleontological resource, the Hamilton Group brachiopods have been largely ignored over the past few decades in terms of their systematics and potential biostratigraphic value. A detailed systematic study of brachiopods collected from exposed strata of the Hamilton Group in the Arkona-Thedford-Ipperwash area of southwestern Ontario has led to the recognition of 50 species assigned to 34 genera, among which one species, Devonochonetes arkonensis n. sp., has been newly defined. A quantitative study of 38 brachiopod associations from the Hamilton Group of southwestern Ontario and equivalent strata in the Appalachian and the Michigan basins, using Q-mode (taxa as variables) and R-mode (localities/ages as variables) cluster analyses, principal component analysis, and four faunal similarity analyses (i.e., Jaccard similarity, Dice similarity, Simpson’s coefficient of similarity, and Raup-Crick similarity indices), has revealed that the late Middle Devonian (Givetian) brachiopod faunas from time-equivalent strata of the Michigan and Appalachian are distinct, allowing identification of two separate faunal subprovinces. In spite of its present-day position in the southeastern part of the Michigan Basin, southwestern Ontario had brachiopod associations which were more similar to those in contemporaneous strata of the Appalachian Basin during the deposition of the lower and middle Hamilton sediments. This may have been related to the absence of a topographic high in the present-day Findlay Arch area that would have otherwise prevented immigration of Appalachian Basin fauna into the study area. During the deposition of the upper Hamilton strata, the southwestern Ontario brachiopod associations developed a closer affinity to those of the Michigan Basin, suggesting that I M'» ii* J jw - ’ » a in O ; Jfiiu t1 prii the immigration of brachiopod faunas from the Appalachian Basin into the study area was impeded. This change in faunal affinity may have been related to the formation of a local arch at present-day Cleveland area of Ohio that blocked the immigration of Appalachian Basin taxa into the study area.
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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 | 0.003 | 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".