An ontogenetic perspective on locomotion in the Late Cretaceous dinosaur<i>Maiasaura peeblesorum</i>(Ornithischia: Hadrosauridae)
Bibliographic record
Abstract
Ontogenetic growth in the forelimb and hindlimb of the dinosaur Maiasaura peeblesorum (Ornithischia: Hadrosauridae) from the Upper Cretaceous (Campanian-Maastrichtian) Two Medicine Formation of Montana is investigated by multivariate and bivariate morphometrics and the biomechanics of beam theory. Results support a hypothesis of an age-dependent selection of stance. Juveniles walked primarily as bipeds. As an individual matured, its predominant stance shifted to quadrupedality. Within the forelimb, morphometric results show a probable allometric enlargement of postural muscles, an allometric increase in the lever arms of protractor muscles, and an increased robustness of the humerus to enhance its resistance to bending stresses. In contrast, the hindlimb is characterized by a relative decrease in the resistance of the femur and tibia to bending stresses. In addition, there is an allometric enlargement of the femoral fourth trochanter and positive allometry of the lengths of metatarsals III and IV. The most likely explanation for the different growth patterns is that the hindlimb was sufficiently robust at a young age to accommodate increased postural and locomotory stresses through largely isometric growth, whereas a behavioral shift to quadrupedality in older individuals necessitated an allometric response in the forelimb. Osteological adaptations for weight-bearing in the manus include metacarpals that are united firmly with a resultant cross-sectional shape that is resistant to bending and hyperextendable joints between the metacarpals and first phalanges. It is probable that flexor muscles that attached to the caudal surface of the metacarpals reinforced the reduced carpus and lessened the likelihood of collapse during quadrupedality.
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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 | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".