<i>Edmontosaurus</i> from the Rocky Mountain foothills, Alberta, and its chronostratigraphic position in the Late Cretaceous Brazeau Formation and correlative units in western Canada
Bibliographic record
Abstract
The Upper Cretaceous Brazeau Formation (early Campanian–early Maastrichtian) near Hinton, AB, preserves dinosaur fossils associated with fluvial and lacustrine palaeoenvironments during a transgressive–regressive cycle within the Western Interior Seaway. Here, the first description of vertebrate remains, hadrosaurid footprints, and radiometric age constraints from the Brazeau Formation are presented. Multiple dinosaur elements were recovered from a new bonebed, including a left postorbital and a partial right postorbital representing Edmontosaurus sp. based on an enlarged postorbital fossa. These are the first dinosaur elements diagnosable to the genus level to have been described from the Brazeau Formation; vertebrate remains have not previously been described from this formation. Eight tephras lie between ∼24 and ∼263 m above the Bennett Bonebed. Seven yielded statistically indistinguishable weighted-average laser ablation zircon 206 Pb/ 238 U dates between 70.14 ± 0.38 Ma (23.75 m) and 69.60 ± 0.35 Ma (∼262.60 m). A Bayesian age-depth model based on the zircon U–Pb dates yields a bonebed age of 70.17 ± 0.42|0.38 Ma and a median sedimentation rate of ∼450 m/Myr across the ∼240 m of measured section. The age of the Bennett Bonebed is, therefore, equivalent to the upper Tolman Member of the Horseshoe Canyon Formation, placing it in the middle Maastrichtian, ∼1.3 Ma after Edmontosaurus regalis is proposed to have been extirpated from Alberta, and within the >2 Ma hiatus of the genus from the fossil record of northwestern North America.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.002 | 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".