Kinetic Limitations of Intracranial Joints in <i>Brachylophosaurus canadensis</i> and <i>Edmontosaurus regalis</i> (Dinosauria: Hadrosauridae), and Their Implications for the Chewing Mechanics of Hadrosaurids
Bibliographic record
Abstract
The highly specialized tooth morphology and arrangement of the dental battery of hadrosaurids has led to much speculation surrounding the chewing mechanics of this successful group of herbivorous dinosaurs. Pleurokinesis, a long established hypothesis explaining the ornithopod chewing mechanism, proposes a transverse power stroke in hadrosaurids that was accommodated by vertical adduction of the mandible, lateral rotation of the maxilla at the maxilla-premaxilla joint, lateral rotation of the jugal-maxilla complex at its contact with the lacrimal, and posterolateral rotation of the quadrate at its contact with the squamosal. A secondary series of movements were also thought to have occurred as a consequence of these primary movements. In this article, the intracranial joint morphology is described for both Brachylophosaurus canadensis and Edmontosaurus regalis and their permissive kinematics are established. Based on this evidence, the movements associated with pleurokinesis are not accommodated in these hadrosaurine dinosaurs. Rather, the movements that seem most likely to have produced the observed dental wear patterns are those associated with the mandible about the jaw joint. The structure of this joint appears well-suited to have accommodated some translation as well as rotation of the mandible about the quadrate condyle. Three-dimensional modeling of the alternate mandibular movements reveals that not all the combined labiolingual width of the lingual and buccal facets of the tooth row was involved in the power stroke. Rather, limits on the degree of mandibular long axis rotation suggest that only the lingual facet and the more medial portion of the buccal facet were utilized.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".