Revision of <i>Habrosaurus</i> Gilmore (Caudata; Sirenidae) and relationships among sirenid salamanders
Bibliographic record
Abstract
The sirenid salamander Habrosaurus is revised and redescribed based on skull elements and vertebrae from the middle Campanian–middle Palaeocene of the North American Western Interior. Habrosaurus differs from the Cenozoic (Eocene–Recent) sirenids Siren and Pseudobranchus in a suite of cranial and vertebral plesiomorphies, one vertebral character of uncertain polarity and five apomorphies describing the structure of the dentary, atlas and tooth crowns. Two species are identified based on dental characters: the type species H. dilatus (late Maastrichtian–middle Palaeocene) has stout marginal and palatal teeth with bulbous crowns and prominent wear facets, whereas H. prodilatus sp. nov. (middle Campanian) has chisel‐like marginal teeth (palatal teeth unknown) with weaker wear facets. Habrosaurus is argued to be the geologically oldest, undoubted sirenid and the sister‐taxon of Siren + Pseudobranchus. Replacement of marginal teeth with a broad, horny beak in Siren and Pseudobranchus and the broad, bulbous marginal and palatal teeth in H. dilatus are proposed to be convergent strategies for achieving a crushing bite. The chisel‐like teeth of H. prodilatus are interpreted as being transitional to the more specialized, crushing dentition of H. dilatus.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 0.002 |
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".