Large Carnivorous Dinosaurs with Tiny Arms: Why Tyrannosaurus rex had Relatively Short Forelimbs
Bibliographic record
Abstract
Tyrannosaurus rex (T. rex) is perhaps the most famous non-avian dinosaur due to its large size, ferocity, and portrayal in popular culture. T. rex was the apex predator of its time and dominated parts of North America during the Late Cretaceous around 66 million years ago. This theropod ranged from 12–13 meters in length and weighed around 7 tonnes. It had long, serrated banana-shaped teeth adept at crushing bone, a skull length of around 1.2 meters, and the most powerful jaws of any land animal ever to have lived. Curiously, T. rex had highly reduced forelimbs approximately 28% of its hindlimb length. The purpose of this paper is to discuss why T. rex had such proportionally short forelimbs, and what, if anything, they were used for. Proposed functional hypotheses range from signaling to holding prey to slashing. Hypotheses aiming to describe the mechanism behind reduction have included a compensatory relationship, where forelimb reduction is linked to the increase in skull size for more effective predation. Additionally, selective pressures from group feeding may have favoured reduction, as shorter forelimbs would reduce vulnerability to injury. These hypotheses and conclusions are discussed in terms of phylogenetics, behavioural ecology, and a literature-based assessment.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".