Crocodylian and dinosaur trace fossil assemblages from crevasse splay/levee and floodplain lake environments: middle Cenomanian Dunvegan Formation, northeast British Columbia, Canada
Bibliographic record
Abstract
Delta-plain strata of the Cenomanian Dunvegan Formation, in north-east British Columbia, represent anastomosed rivers that were flanked by vegetated crevasse splays, wetlands and shallow lakes. These rocks preserve a rich record of ankylosaur and ornithopod walking and wading tracks, as well as crocodylian swim traces and tracks. Analysis of depositional, erosional, and trace-making events reveals alternating phases of flooding and emergence that controlled both animal activity (walking, wading, swimming) and mud substrate consistency (firm vs. soupy), and hence fidelity of track preservation. Some tracks resemble those produced by both ankylosaurs and crocodylians, and confident attribution is difficult. The absence of tail drag marks suggests an ankylosaur trackmaker, whereas prominent claw marks might favour a crocodylian origin. Unusually large crocodylian swim traces suggest animals about 9 m, and possibly up to 12 m in length. These large traces may represent a precursor to the giant crocodylian Deinosuchus. Ankylosaur tracks are well-preserved in lake and channel-margin deposits, whereas crocodylian traces are most commonly preserved in firm muddy lake sediments that had experienced previous subaerial exposure and dewatering. Close integration of trace fossils with sedimentary and stratigraphic features makes it possible to reveal a detailed chronology of biotic and sedimentary events on palaeo-surfaces.
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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 | 0.004 | 0.006 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".