Ordovician and Silurian nautiloid cephalopods from Anticosti Island: traject across the Ordovician–Silurian (O–S) mass extinction boundary
Bibliographic record
Abstract
Well-preserved shells of Ashgill (Katian–Hirnantian) and Llandovery nautiloids from Anticosti Island include the type species of 10 genera. From a diversity high of some 40 described nektic and nektobenthic species during the deeper water, distal shelf facies of the Vaureal Formation (late Katian, Richmondian), the succeeding Hirnantian shows a decline to ca. 19 species in the shallower water Ellis Bay Formation. A number of Katian species possessed very large orthoconchs (>1 m in length), but Hirnantian species were less than half that size. The initial earliest Silurian (Rhuddanian, Becscie Formation) recovery nautiloid fauna is impoverished, with low diversity (one sp.?), and generally dwarfed, to shells with diameters of <1 cm. Nautiloid diversity expanded and progressed to some 22 species in the late Aeronian through Telychian Jupiter and Chicotte formations, with an apparent peak in the Goéland Member of the Jupiter Formation. Three new species, Actinoceras lesperancei , Eridites barnesi , and Diestoceras macgilvrayoceras , are described. The distribution of shells within the succession defines the fauna’s stratigraphic and paleobiogeographic significance, with a changing mix of Baltic and Laurentian taxa.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.000 |
| Open science | 0.000 | 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".