Diversity dynamics of Early Jurassic ostracods of the Cordillera Ibérica (Spain) and the re-evaluation of the Pliensbachian–Toarcian mass extinction
Bibliographic record
Abstract
The extinction and recovery of Ostracoda at the Pliensbachian–Toarcian (P–T) boundary are analyzed based on a database of taxonomically revised Pliensbachian to Toarcian transition ostracod assemblages. In contrast to earlier assertions, the results of this study indicate that ostracod extinction rates were significant in comparison with other marine invertebrates. An extinction rate of 54% has been calculated for upper Pliensbachian ostracod species occurring in more than one section. Diversification took place in the latest Pliensbachian (Spinatum Zone) and early Toarcian (Tenuicostatum Zone), whereas diversity decrease occurred in the middle early Toarcian (Strangewaysi Subzone, Serpentinus Zone). This notable diversity decline in the early Toarcian corresponds to a global mass extinction time, whose peak has been documented in the Tenuicostatum Zone. Meanwhile, the ostracod mass extinction occurred within the Serpentinus Zone and was followed by radiation and recovery in the succeeding Bifrons Zone. Similar diversity changes of ostracods are observed in other European areas, although in the Cordillera Ibérica, the demise began later. Many aspects of this event are still debated, and there is no common cause or single set of climatic or environmental changes common to this event. The supposed extinction-causing environmental changes resulting from anoxia episodes are unclear and are unlikely to have been of sufficient intensity or geographic extent to cause this global extinction. In this paper, the decrease in marine species diversity is explained by a new palaeoceanographic scenario, in which a rapid global cooling episode is regarded as the ultimate cause.
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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".