A Re-evaluation of the Chasmosaurine Ceratopsid Chasmosaurus (Dinosauria: Ornithischia) from the Upper Cretaceous (Campanian) Dinosaur Park Formation of Western Canada
Bibliographic record
Abstract
The chasmosaurine ceratopsid Chasmosaurus is known from the Upper Cretaceous (Campanian) Dinosaur Park Formation (DPF) of southern Alberta and Saskatchewan. The two valid species, Chasmosaurus belli and Chasmosaurus russelli, are distinguished by differences in cranial ornamentation, and their purported stratigraphic segregation in the DPF, with C. russelli replaced by C. belli over time. In the DPF, Chasmosaurus is replaced by a third chasmosaurine, Vagaceratops irvinensis. A specimen-based phylogenetic analysis of Chasmosaurus and Vagaceratops recovered Vagaceratops (CMN 41357 and TMP 1987.045.0001) as a sister taxon to Chasmosaurus, and not to Kosmoceratops as per previous analyses. All but two Chasmosaurus specimens formed a single, unresolved group in the 50% majority rule analysis. AMNH 5402 and YPM 2016 were recovered within the 'Vagaceratops' clade. This clade shares anteroposteriorly shortened parietal fenestrae, and a straight posterior parietal margin, adorned on each side with five epiossifications. The remaining Chasmosaurus-like specimens all possess anteroposteriorly elongate parietal fenestra, and a variably embayed posterior parietal margin, adorned on each side with three epiossifications. A stratophylogenetic analysis demonstrated that no stratigraphic separation exists between C. belli and C. russelli, or between Chasmosaurus-like and Vagaceratops-like specimens. These previously unreported temporal overlaps resulted from the recent rediscovery of the C. russelli holotype (CMN 8800) quarry in the uppermost DPF, and the assignment of YPM 2016 (middle DPF) to the Vagaceratops-like group. An ontogenetic analysis demonstrated that C. belli and C.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".