Anisian (Middle Triassic) ammonoids from British Columbia (Canada): biochronological and palaeobiogeographical implications
Bibliographic record
Abstract
Abstract New Anisian (Middle Triassic) ammonoids are reported from British Columbia (BC), Canada. Eight species are reported, including one new genus and two new species:Eofrechites roopnarinigen. et sp. nov. andParafrechites cordeyisp. nov. New ammonoid subzones are recognized, leading to improved correlation betweenBCand Nevada: theHollandites minorZone is correlated with the interval intercalated between theUnionvillites hadleyiSubzone and thePseudodanubites nicholsiSubzone; anEogymnotoceras thompsoni–Anagymnotoceras spivakiZone is recognized inBCand correlated with the interval intercalated between theAugustaceras escheriandAnagymnotoceras spivakisubzones;Gymnotoceras weitschatiis found inBCfor the first time and co‐occurs withEogymnotoceras deleeni, suggesting either a rough correlation with the sum ofG. weitschati,G. mimetusandG. rotelliformiszones of Nevada or a strong diachronism ofG. weitschatiandG. rotelliformisalong the Palaeopacific margin of North America. The rare occurrences of low‐palaeolatitude restricted species in the mid‐palaeolatitude record indicate that exchanges were more frequent than previously documented during the Anisian. Despite a preservation bias in north‐easternBCdue to the lower carbonate content, it clearly emerges that the enhanced sampling effort leads to maximal association zones with duration of the same order of magnitude as those of Nevada, indicating that evolutionary turnover rates of ammonoids did not decrease toward higher latitude. Therefore, the common view that geographically differentiated evolutionary rates originates from the latitudinal gradient of taxonomic richness does not hold for Anisian ammonoid faunas along the Palaeopacific margin of North America.
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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 | 0.005 |
| Science and technology studies | 0.003 | 0.001 |
| 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".