The postcranial skeleton of the aquatic parareptile <i>Mesosaurus tenuidens</i> from the Gondwanan Permian
Bibliographic record
Abstract
The postcranial skeleton of Mesosaurus tenuidens, a reptile from the Lower Permian of eastern South America and southern Africa, is redescribed and illustrated in detail. The number of presacral vertebrae varies in M. tenuidens from 29 to a maximum of 33, which falls just short of the maximum (34–35 presacrals) known in its close relative Stereosternum tumidum. A cleithrum is reported for the first time in a mesosaur. The head of the interclavicle is triangular, rather than diamond-shaped as in other basal reptiles, including S. tumidum. The carpus of M. tenuidens is apomorphic in that the intermedium and the lateral centrale are coossified. The lateral centrale pedis is absent. Reappraisal of the aquatic adaptations of M. tenuidens suggests strongly that this reptile was fully dedicated to an aquatic lifestyle. Pervasive pachyostosis of the postcrania probably allowed animals to maintain neutral buoyancy in the uppermost 3–4 m of the water column. Additionally, such pachyostosis may have helped to control rolling at the surface, or perhaps served to maintain forward momentum during periods of gliding while moving underwater. Limited movement at the elbow and the ankle suggests that M. tenuidens could not walk on land, but individuals may have been able to push themselves across terrestrial substrates, perhaps in a manner analogous to that seen in female extant marine turtles on nesting beaches.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".