A histological investigation of dental crown characters used in mosasaur phylogenetic analyses
Bibliographic record
Abstract
Mosasaur researchers have used varieties of tooth crown ornamentation as diagnostic and phylogenetic characters for decades. Such tooth crown features include facets, flutes, striations, serrated carinae, and coarse anastomosing texture. This study investigates the relative contribution of dentine and enamel to the development of these dental characters and assesses possible homologies between these structures. Histological analysis of isolated mosasaur teeth revealed that flutes and facets develop initially from the dentine, and the external enamel morphology we observe macroscopically mirrors the shape the underlying dentine. Striations combine underlying contributions from the dentine with additional and irregular enamel deposition that results strictly from amelogenesis. In both serrated carinae and anastomosing texture the border between the dentine and the enamel is smooth, and these external ornamentations form through variations in enamel development. Based on these observations, we infer that flutes and facets are part of a morphological spectrum and should not be treated as separate phylogenetic characters. Conversely, striations develop differently than flutes and facets, and should therefore be treated as a distinct character. We recommend referring to the “serrations” on mosasaur carinae as crenulations to differentiate these enamel-only structures from true denticles possessing a dentine core. Anastomosing texture can also coincide with significant apical thickening, both of which could be adaptations for processing hard-shelled prey. Care must be taken when using tooth crown features as diagnostic or phylogenetic characters because seemingly different morphologies can have similar developmental origins, and tooth morphology can be more closely tied to diet than to common ancestry.
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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) | 0.000 | 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 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".