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
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.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".