A latest Eocene (Chadronian) brontothere (Mammalia, Perissodactyla) from the Antero Formation, South Park, Colorado
Bibliographic record
Abstract
ABSTRACT Late Eocene brontotheres are documented most prevalently from formations in the Great Plains of North America. Here we describe UCM 109045, a mandible and lower dentition of a brontothere recovered from a latest Eocene (Chadronian) locality in the Antero Formation in South Park, Colorado. This is a high-altitude locality in which vertebrate fossils are rare. Lower incisor number and presence of a long postcanine diastema indicate that UCM 109045 does not belong to Megacerops coloradensisLeidy, 1870, by far the most abundant brontothere from the Chadronian North American Land Mammal Age. Instead, UCM 109045 is morphologically most similar to Protitanops curryiStock, 1936, from the early Chadronian of the southwestern United States, and nomen dubium Megacerops primitivusLambe, 1908, from the Chadronian of Saskatchewan, Canada. It is possible that Megacerops kuwagatarhinusMader and Alexander, 1995, is a junior synonym of M. primitivus. If UCM 109045 belongs to Megacerops primitivus (= M. kuwgatarhinus), it would support the hypothesis that only two species of brontothere—M. primitivus (= M. kuwgatarhinus) and M. coloradensis—survived into the latest Eocene. Regardless of its exact identification, the discovery of UCM 109045 in the Antero Formation provides insight into a poorly understood, high-altitude locality in North America from just before brontothere extinction at the Eocene–Oligocene boundary.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| 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".