Taxonomic problems across the Cambrian-Ordovician boundary
Bibliographic record
Abstract
The GSSP (Global Boundary Stratotype Section and Point) of the Cambrian-Ordovician boundary was formally defined in 2000 in the Green Point section, western Newfoundland, Canada (Cooper, 2001) at a level coinciding with the FAD (First Appearance Datum) of Iapetognathus fluctivagus, below the appearance of planktic graptolites. \nAttempts to correlate the GSSP section with other areas proved to be problematic. \nThese problems arise not only from the fact that Iapetognathus is rare in many regions, but they are mostly related to taxonomic bias, not only of the above mentioned genus, but also of other taxa spanning the Cambrian-Ordovician boundary. \nMain problem: taxonomy of Iapetognathus at generic and specific level. \nOther taxa that are, or have been used for recognition of the Cambrian-Ordovician boundary are species of the genus Cordylodus. Cordylodus is perhaps the most common and characteristic genus this interval. Cordylodus is the first euconodont genus that exhibits a complex apparatus with ramiform elements. It was very successful and its rapid diversification produced a relevant number of species that have recovered in abundance in most continents. For the taxonomy of the species of Cordylodus one of the main feature is the depth and shape of basal cavity. Among these, a species that might be helpfull to recognize the Cambrian-Ordovician boundary is Cordylodus lindstromi. \nUnfortunately the taxonomy of this species needs some refinements. Nicoll (XXX) provided a revision of species of Cordylodus, including C. lindstromi, and later Nicoll (XXX) introduced C. prolindstromi. Nevertheless is common to see in several papers C. lindstromi sensu lato and C. lindstromi sensu stricto. \nGraptolites \nDayangcha has excellent potential to clarify and improve correlations, owing to its rich content in conodonts. In Dayangcha also trilobites and acritarchs are present, and in particular the first planktic graptolites currently under study by Maletz. \nChemostratigraphy can also be an important tool, with a geochemical anomaly just before the boundary interval that has been recognized both in the GSSP section and in the Dayangcha section.
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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 | 0.011 | 0.023 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.006 | 0.007 |
| Science and technology studies | 0.006 | 0.005 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.004 | 0.004 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".