The skull and the palaeoecological significance of Labidosaurus hamatus, a captorhinid reptile from the Lower Permian of Texas
Bibliographic record
Abstract
The cranial skeleton of the large captorhinid reptile Labidosaurus hamatus, known only from the Lower Permian of Texas, is described on the basis of new, undescribed specimens. Labidosaurus is distinguished from other captorhinids by the more extreme sloping of the ventral (alveolar) margin of the premaxilla, a low dorsum sellae of the parabasisphenoid, a reduced prootic, a narrow stapes, and a relatively small foramen intermandibularis medius. Despite the presence of a single row of teeth in each jaw, the skull of Labidosaurus resembles most closely those of moradisaurines, the large multiple-tooth-rowed captorhinids of the latest Early and Middle Permian. A phylogenetic analysis confirms that the single-tooth-rowed L. hamatus is related most closely to moradisaurines within Captorhinidae, a relationship that supports the hypothesis of a diphyletic origin for multiple rows of marginal teeth in captorhinids (in the genus Captorhinus and in the clade Moradisaurinae). In view of the close relationship between L. hamatus and moradisaurines, which are regarded to have been herbivorous, L. hamatus is a critical taxon for studies of the evolution of herbivory in early tetrapods. L. hamatus shares several trademark features of herbivorous adaptation with moradisaurines, which suggest that this captorhinid species was omnivorous. As such, it represents a transitional taxon between faunivorous basal reptiles and the herbivorous moradisaurines.
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".