Onshore migration of a deep-water brachiopod fauna from the Lower Ordovician Tonggao Formation, Jiangnan Slope, southeastern Guizhou Province, South ChinaThis article is one of a series of papers published in this Special Issue on the theme <i>The dynamic reef and shelly communities of the Paleozoic. This Special is in honour of our colleague and friend Paul Copper</i>.
Bibliographic record
Abstract
Brachiopods from the lower Tonggao Formation (Floian, late Early Ordovician) of Sandu, southeastern Guizhou Province, represent a deep-water benthic shelly fauna from the Jiangnan Slope facies of the South China paleoplate. The fauna contains 16 brachiopod taxa, with orthides, lingulates, and pentamerides being the common groups. Concurrent graptolites confine the brachiopod fauna to the Tetragraptus approximatus and the Acrograptus filiformis biozones (early Floian). The first appearance datum (FAD) of several brachiopod genera, such as Paralenorthis , Protoskenidioides , and Nereidella , in the Sandu slope facies is one or two graptolitic biozones lower than their FAD in shallower water facies on the Yangtze Platform. Later in the late Floian, these genera became major components of the Sinorthis fauna that flourished over much of the Yangtze Platform, suggesting a migration of the benthic shelly fauna from slope to platform facies during the Floian radiation in South China. Compared to the platform fauna, the deep-water brachiopod fauna of the Sandu area has a lower level of richness, diversity, and community organization. Three brachiopod associations are recognized: the Paralenorthis–Nereidella, the Palaeoglossa longa , and the Lingulella –Protoskenidioides associations. An upsection decrease in shell size, faunal richness, and species diversity in the Tonggao Formation indicate a deteriorating environment towards hypersalinity in the Sandu area, resulting in the ultimate disappearance of the deep-water brachiopod fauna.
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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 | 0.000 |
| Scholarly communication | 0.000 | 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".