Small cordaitalean trees in a marine-influenced coastal habitat in the Pennsylvanian Joggins Formation, Nova Scotia
Bibliographic record
Abstract
The Cordaitales, an extinct order of plants closely related to the conifers, occupied a wide range of environments during Pennsylvanian times including wetlands, drylands, and uplands. However, claims that some species of cordaitalean grew on marine-influenced coastal margins, and therefore represented the earliest known mangrove communities, have been met with scepticism. Based on new data from the Joggins Formation of Nova Scotia, the ‘cordaitalean mangrove hypothesis’ is reassessed. Small fossil trees in growth position are described from micro-tidal deposits, a sedimentary association inferred to have formed on the margins of a brackish epicontinental sea. The autochthonous trees, which are morphologically different from lycopsid and calamitean trees commonly observed with the Joggins Formation, are probably cordaitalean. This affinity is indicated, in part, by facies-associated parautochthonous remains, which comprise Cordaites leaves, Cordaicladus branches, Cardiocarpus seeds, Cordaianthus reproductive organs, and Dadoxylon wood, a distinctively cordaitalean assemblage. Scour-and-mound structures in beds surrounding the upright trunks show that cordaitalean trees were, at times, submerged in shallow, flowing water. However, Limnopus tetrapod trackways at other horizons demonstrate periodic emergence, indicating that water depths fluctuated in these coastal forests. Analysis of rooting patterns shows that trees persisted through flooding events, despite partial burial by sheets of very fine sandstone and siltstone, survival being facilitated through the development of an adventitious rooting system. However, two key adaptations to growth in marine-influenced soils commonly seen in modern mangrove trees (low shoot:root ratios and small leaves) are not present in the cordaitalean trees. Furthermore, although the trees probably grew in close proximity to the brackish seacoast, direct evidence for marine influence in the fossil forest interval itself is lacking. Consequently, although the cordaitaleans were probably adapted to periodically submerged conditions, and additionally may have tolerated occasional brackish incursions, it is inappropriate to describe them as mangroves in the strict sense.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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".