Extreme faunal endemism, super-island faunas, and the Late Ordovician mass extinction
Bibliographic record
Abstract
The majority of studies on mass extinction events (MEEs) have focused on the various extrinsic or palaeoenvironmental killing mechanisms, most associated with habitat destruction and some of which remain hotly contested. The ‘ mass extinction by insularization and kill ’ (MEIK) model of this study is proposed as a significant intrinsic cause of the Late Ordovician MEE based on palaeoecological and palaeobiogeographical analyses of Ordovician brachiopod faunas from Laurentia and its adjacent tectonic plates. During the Late Ordovician pulses of a first-order sea-level rise, the MEIK model reveals that biodiversity hotspots shifted from open ocean to epicontinental seas associated with a drastic increase in faunal endemism. Continental-sized ‘island faunas’, exemplified by the Laurentian intracratonic-sea brachiopods, were characterized by high abundance but relatively low diversity, but more critically the eventual loss of their inter-plate dispersal ability. The onset of mass extinction of these highly endemic ‘super-island’ faunas, specialized in living in shallow intracratonic seas for ~8 million years during the Katian, occurred at the start of the Hirnantian glaciation due to draining of epicontinental seas and loss of their specialized habitats. The data presented here suggest that during a major sea-level rise, global biodiversity epicentres migrated from the ocean to epicontinental seas, becoming genetically isolated, rendering marine shelly benthos intrinsically susceptible to rapid environmental change and subsequent mass extinction.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 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) | 0.001 | 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".