A new record of <i>Megalonyx</i> (Xenarthra, Megalonychidae) from the Pliocene of Mexico: a new addition to the megalonychid diversity from the late Cenozoic of North America
Why this work is in the frame
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Bibliographic record
Abstract
In this study, the Blancan (Pliocene) ground sloth material from the Los Hornitos locality, northeastern Sonora, northern Mexico, is described. The Mexican fossil record of the Pilosa is somewhat rare, documenting the dispersal of members of the Megalonychidae and other sloth families from South America to North America. The sample comprises six isolated teeth and a patella. We reconstructed the diet based on isotopic analysis (δ13C and δ18O) of teeth and indirectly inferred the habitat preference of the studied megalonychids. Our results suggest a diet predominantly consisting of C3 plants as in other Cenozoic ground sloths. The morphology of the Sonoran specimens best fits with Megalonyx leptostomus, although the sample size and the dental variation in this genus limit their species identity. This is the oldest Megalonyx in Sonora and the first record of the genus from the Pliocene of Mexico, connecting the Late Miocene records of Megalonyx sp. to those of M. wheatleyi and M. jeffersonii from the Early and Late Pleistocene. This record adds to the diversity of Mexican Megalonychidae, consisting of six genera and about 10 species, three times the number of genera and 40% greater than the species diversity for the United States of America and Canada.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 it