A dipterid-grade lungfish from the Tournaisian Horton Group of Nova Scotia, Canada
Bibliographic record
Abstract
ABSTRACT Lungfishes achieved high diversity in the Devonian, but most of these lineages went extinct in the late Devonian mass extinctions. Carboniferous lungfish are generally thought to belong to one larger diversification, Phaneropleuriformes, typically associated with freshwater and estuarine environments. We here use μCT to describe a lungfish occiput from the Tournaisian of Blue Beach, Nova Scotia, Canada, the first lungfish occurrence from the Tournaisian of North America. The occiput is short and high with well-developed dorsolateral cristae, two pairs of spinal nerves posterior to the vagus nerve, and a short triangular posterior stem of the parasphenoid. Although this specimen is too incomplete to place into a phylogenetic analysis, we identify characteristics shared with both holodontids and dipterids and absent within Phaneropleuriformes, suggesting the persistence of a wider range of lungfish lineages through the end-Devonian mass extinction events, in line with recent findings from the Tournaisian-aged Ballagan Formation of Scotland. Differences in the faunal composition of the Blue Beach Member of Nova Scotia and the Ballagan Formation of the Scottish Borders may be a consequence of different paleoenvironments in these roughly coeval formations or of palaeobiogeographical barriers to dispersal between Europe and Atlantic Canada. The possible persistence of a marine or estuarine lungfish into the mid-Tournaisian shows turnover of the marine durophage guild across the Hangenberg extinction was not complete, but may have been sufficient to disrupt incumbency in earliest Carboniferous marine trophic guilds.
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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 | 0.002 | 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".