Oldest skeleton of a plesiadapiform provides additional evidence for an exclusively arboreal radiation of stem primates in the Palaeocene
Why this work is in the frame
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Bibliographic record
Abstract
Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recognized as among the oldest and most primitive euarchontan mammals, a group that includes extant primates, colugos and treeshrews. Despite their relatively sparse fossil record, palaechthonids have played an important role in discussions surrounding adaptive scenarios for primate origins for nearly a half-century. Likewise, palaechthonids have been considered important for understanding relationships among plesiadapiforms, with members of the group proposed as plausible ancestors of Paromomyidae and Microsyopidae. Here, we describe a dentally associated partial skeleton of Torrejonia wilsoni from the early Palaeocene (approx. 62 Ma) of New Mexico, which is the oldest known plesiadapiform skeleton and the first postcranial elements recovered for a palaechthonid. Results from a cladistic analysis that includes new data from this skeleton suggest that palaechthonids are a paraphyletic group of stem primates, and that T. wilsoni is most closely related to paromomyids. New evidence from the appendicular skeleton of T. wilsoni fails to support an influential hypothesis based on inferences from craniodental morphology that palaechthonids were terrestrial. Instead, the postcranium of T. wilsoni indicates that it was similar to that of all other plesiadapiforms for which skeletons have been recovered in having distinct specializations consistent with arboreality.
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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 | 0.002 | 0.000 |
| 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 | 0.000 | 0.001 |
| Open science | 0.003 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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