Insights into the biostratigraphy of the Silurian–Devonian transition in Southwestern Gondwana, based on a new graptolite record from Argentina
Bibliographic record
Abstract
The Silurian-Devonian transition witnessed not a single mass faunal turnover but minor extinctions and recovery intervals. Planktonic graptolites experienced a reduction in diversity before their extinction in the Early Devonian. Due to the scarce fossil record from high-latitude cold waters, these interpretations have been primarily based upon the best known low-latitude faunas. The graptolite herein presented is the first record of latest Silurian to possibly Devonian age from high southern paleolatitudes of Gondwana. A new fossil locality of the Argentine Precordillera yielded Slovinograptus ? microdon curvatus , previously found only in the Canadian Arctic. This is the youngest Silurian graptolite record in south-western Gondwana, constituting a useful global biostratigraphic marker. The fossil-bearing strata can, at least partially, be correlated with the latest Silurian Uncinatograptus birchensis Zone, and can be referred to the latest Pridolian in accordance with evidence from the co-occurring brachiopod assemblage, as well as from conodont data from equivalent stratigraphic sections. Furthermore, the brachiopod faunal turnover recorded in the studied stratigraphic section potentially correlates with the Transgrediens Extinction Event, a biotic crisis not older than latest Pridolian. Evidence suggests that the brachiopod (and probably the trilobite) turnover and the concomitant biogeographic reconfiguration of provincialism of Gondwanan benthic faunas around the Silurian-Devonian boundary might be related to the aftermath of the Transgrediens Event.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".