Comments on Fernández et al. (2025): clarifying a misinterpretation of the Itaboraí Basin estimated age
Bibliographic record
Abstract
Fernández et al. (2025) favoured the previous chronological hypothesis of an early Eocene age for the Itaboraí Basin, Brazil, based on the isotopic dating of the ankaramite (~54.89 Ma) and a single fossil vertebrate (~55 Ma), but overlooked that this locality may range from late Palaeocene to early Eocene in age. Fernández et al. (2025) statement suggested that Bergqvist et al. (2024) proposed a unique late Palaeocene age for the Itaboraian SALMA; however, this likely stems from a misunderstanding of their proposal. The age estimation made by Woodburne et al. (2014) for the Itaboraian SALMA (53–50 Ma, contemporaneous to the Early Eocene Climatic Optimum) cannot be applied to the entire basin, as this locality preserved multiple fossiliferous strata (Itaboraí I/MCT-2 fissure and Itaboraí II/Itaboraian SALMA [MN and MCT-1; type faunas]). Additionally, the dates provided by the isotopic dating are unfit to confidently establish the age of the Itaboraí faunas, as their topographic and stratigraphic relationships within the basin remain undefined and cannot be further investigated because the limestone has been almost completely exploited. Bergqvist et al. (2024) considered only the fauna from the MCT-2 fissure as latest Palaeocene-earliest Eocene in age.
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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 | 0.010 | 0.067 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.006 | 0.006 |
| Scholarly communication | 0.004 | 0.005 |
| Open science | 0.006 | 0.004 |
| Research integrity | 0.022 | 0.025 |
| Insufficient payload (model declined to judge) | 0.005 | 0.007 |
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".