A marginal marine fauna from the upper Dinosaur Park Formation, Canada
Bibliographic record
Abstract
During the Late Cretaceous, the coastline of the epicontinental Western Interior Seaway in North America fluctuated in position, temporarily replacing some terrestrial ecosystems with shallow marine habitats.In southeastern Alberta, the uppermost portion of the Dinosaur Park Formation (Belly River Group, late Campanian) preserves one of these transgression–regression cycles in a marine wedge named here as theJohnson Unit. We report the stratigraphy of the unit based on nine stratigraphic sections over several kilometres of exposure. We describe a diverse assemblage of marine vertebrates from the Johnson Unit, represented by microfossils from a surface collecting survey. Our sample includes 1431 specimens, which we assign to 40 taxa. We identify eight new actinopterygians from the unit: Belonostomus longirostris, Amiidae indet.,Elopiformes indet., Horseshoeichthys sp., Enchodus gladiolus, Dercetis cf. D. magnificus, Acanthomorpha indet., and teleost indet. type O. The acanthomorph specimens, which include isolated spines and centra, represent the second marine Cretaceous acanthomorph reported from Alberta, and the highly ornamented spines are unlike any previously described. We revise several chondrichthyan identifications from previous authors and describe partial tooth plates from the chimaeriform Ischyodus bifurcatus for the first time in Canada. Compared to earlier samples from the same unit that were collected using screen-washing, our sample has ahigher diversity of actinopterygians and tetrapods. We identify several taxa to lower taxonomic levels using more complete specimens. These differences are attributed to our use of surface collection; this method allowed novel biogeographic and taxonomic insights.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.020 | 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; both teacher heads agree on what is shown here.
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".