Consilient evidence affirms expansive stabilizing ligaments in the tyrannosaurid foot
Bibliographic record
Abstract
Tyrannosaurid dinosaurs were ecologically unique vertebrates as the sole clade of large terrestrial carnivores (adults >400 kg) in their continent-spanning habitats. Expanded ligaments between metatarsals, inferred by gross morphology of attachment correlates, have been hypothesized to have strengthened their specialized arctometatarsus. We tested the hypothesis of ligament presence with scanning electron microscopy and histological thin sections of putative attachment sites in a third metatarsal of the tyrannosaurid Gorgosaurus libratus, compared with a thin section from the unspecialized metatarsals of the early theropod Coelophysis bauri. In the Gorgosaurus metatarsal, Sharpey´s fibers and rough, pitted surface textures consistent with ligament coalescence occur at expansive distal regions and localized rugosities are ideally located for resisting torsional loading on the foot. Sparser Sharpey’s fibers occur at expected locations in other arctometatarsus-bearing coelurosaurs. In contrast, the Coelophysis metatarsal lacked Sharpey’s fibers or rugosity at the sectioned location, acting as a definitive negative control for identifying these features in tyrannosaurids. With soft-tissue correlates confirmed as ligament entheses, we conclude that tyrannosaurids possessed distinctive and specific ligament attachments to the third metatarsal lacking in other large carnivorous dinosaurs. Histological evidence for extensive distal intermetatarsal ligaments is consistent with greater inferred agility in derived tyrannosaurid dinosaurs than in earlier lineages of large theropods.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".