Description of juvenile specimens of Prosaurolophus maximus (Hadrosauridae: Saurolophinae) from the Upper Cretaceous Bearpaw Formation of southern Alberta, Canada, reveals ontogenetic changes in crest morphology
Bibliographic record
Abstract
Three juvenile specimens of Prosaurolophus maximus, represented by articulated to disarticulated skeletons, are the smallest known individuals for the taxon. Cranial anatomy of the juvenile specimens indicates that diagnostic characters of P. maximus are ontogenetically variable. In the smallest individual, the crest and deeply excavated fossa at the caudal margin of the circumnarial depression are poorly developed or absent. The crest approaches adult-like morphology in large juveniles, whereas crest robusticity and the deep excavation of the circumnarial depression occur only in subadult and adult individuals. The shape of the caudal margin of the circumnarial depression is consistent between juvenile and adult individuals, potentially making this feature a reliable character for taxonomic identification at younger ontogenetic stages. The crest of P. maximus grows isometrically during ontogeny, unlike the positive allometric growth of lambeosaurine hadrosaur crests, suggesting that this taxon may have had soft tissue structures associated with the narial-crest region, rather than the bony crest itself, selected for sexual display. Recovered from sediments of the Bearpaw Formation deposited during the Baculites compressus ammonite zone and magnetochrons 33n.3n to 33n.2n, the juvenile specimens are stratigraphically younger than P. maximus specimens from the Dinosaur Park Formation (Alberta) and contemporaneous with most specimens from the Two Medicine Formation (Montana), extending the temporal range of the taxon to 75.7–74 Ma. The occurrence of P. maximus in well-drained terrestrial deposits of the Dinosaur Park and Two Medicine formations and marine sediments of the Bearpaw Formation indicates that this taxon inhabited various paleoenvironments in western 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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".