When teeth and bones disagree: body mass estimation of a giant extinct rodent
Bibliographic record
Abstract
Body size is correlated with virtually every morphological, physiological, and life-history trait in mammal species. As a consequence, estimates of body size of fossil species are often used for paleoecological reconstructions. Characters used as proxies for body mass in extinct species include teeth, skull, and skeletal measurements. We show that the body-mass estimates of extinct species from living taxa can be misleading and depend largely on the morphological variable selected as a proxy for body mass. We also discuss statistical tools that are available to assess the accuracy of body-mass estimates in extinct species. Here, we focus on the revision of the mass estimate of the giant Miocene fossil rodent Phoberomys pattersoni (Venezuela), the 2nd largest rodent ever reported, with an estimated body mass between 436 and 741 kg. This is far beyond the range of average body masses in living rodents, which vary from several grams to 40 kg. We conclude that body mass of Phoberomys was most likely overestimated. The species P. pattersoni likely weighed between 220 kg and 280 kg, the mass of a horse or a large antelope.
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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 | 0.003 | 0.012 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".