A new specimen of Chasmosaurus belli (Ornithischia: Ceratopsidae), a revision of the genus, and the utility of postcrania in the taxonomy and systematics of ceratopsid dinosaurs
Bibliographic record
Abstract
A previously undescribed chasmosaurine specimen excavated in 1919-1920 by William Cutler from the Dinosaur Park Formation of Alberta, Canada is referable to Chasmosaurus belli. The specimen comprises an almost complete skull in which, uniquely among Chasmosaurus, the cranial elements are disarticulated, allowing detailed examination of their morphology for the first time. The complete braincase is present and allows comparison with the braincase of other ceratopsians. The specimen also preserves an uncrushed and undistorted postcranium, including cervical, dorsal and sacral vertebrae and limb elements. The vertebral column of Chasmosaurus has never previously been described in detail, and NHMUK R4948 affords the opportunity to examine it because of the unparalleled state of vertebral preservation. A proliferation of new chasmosaurine genera has recently been described; many of them differ from each other only in details of frill and epiparietal morphology. Several of these are based on specimens previously referred to Chasmosaurus. As a result, the characters that distinguish Chasmosaurus from other Campanian chasmosaurines are unclear. However, the genus Chasmosaurus and species within the genus are diagnosable and valid based on unique combinations of characters and frill morphology. Detailed examination of the postcranial morphology of a variety of centrosaurines and chasmosaurines has highlighted previously undescribed synapomorphies for the two major ceratopsid clades, concentrated in the pectoral girdle and forelimb. Inconsistencies in the vertebral formula of specimens referred to Chasmosaurus belli suggests that the postcrania of ceratopsids may vary between species and genera far more than previously thought, and that postcranial characters should be incorporated into phylogenetic and taxonomic studies.
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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 | 0.002 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".