Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), IV: the oldest edentulous frog (Salientia) from Laurasia
Bibliographic record
Abstract
Edentulism—lack of teeth—is a derived condition among salientians (total-group frogs and toads) that has arisen independently at least 22 times within the crown group, Anura. Despite this frequency, edentulism (in part or complete) is seldom documented in the salientian fossil record, and thus its evolutionary history remains obscure. A ∼90 Ma gap presently exists between the edentulous salientians Notobatrachus reigi (late Toarcian; Argentina) and the five known species from the latest Cretaceous of Argentina, South Africa, Canada, and the U.S.A. Here we report a new instance of edentulism in an Early Cretaceous salientian, Ostrombatrachos nodos gen. et sp. nov., based on a maxilla from an early Albian age (∼ 111 Ma) locality in the Cloverly Formation of Wyoming, U.S.A. Although incomplete, the holotype maxilla exhibits a distinctive suite of features (i.e., edentulous; pit-and-ridge external ornament; shallow groove across anteriormost portion of margo orbitalis and continuing anteroventrally down lateral surface of pars facialis to interrupt the external ornament; medially expanded orbital flange; moderately broad, deep lamina horizontalis; and weakly developed processus pterygoideus) that is unknown in any other salientian. This new taxon represents the oldest occurrence of edentulous maxillae in a Laurasian salientian and helps fill the long temporal gap in edentulism among salientians. O. nodos gen. et sp. nov. does not appear to be closely related to other edentulous Mesozoic salientians, suggesting it represents yet another independent evolution of this feature.
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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 | 0.001 | 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".