The oldest African crocodylian: phylogeny, paleobiogeography, and differential survivorship of marine reptiles through the Cretaceous-Tertiary boundary
Bibliographic record
Abstract
A gavialoid crocodylian from the Maastrichtian of the Oulad Abdoun phosphatic Basin (Morocco) is described, representing the oldest known crocodylian from Africa. The specimen consists of a skull that exhibits several features not found in other gavialoids, and a new genus and species is erected, Ocepesuchus eoafricanus. A phylogenetic analysis has been conducted including 201 characters and 71 taxa, where Ocepesuchus eoafricanus appears as the most basal African gavialoid, and the South American gavialoids are paraphyletic. This paraphyly has strong biogeographic implications, and the previous hypothesis of South American and Asian assemblages derived from African gavialoids should be reviewed. The historical biogeography of Gavialoidea is probably more complex than previously supposed. The phosphatic deposits of Morocco provide a unique opportunity to study the vertebrate faunal turnover across the Cretaceous-Tertiary (KT) boundary. The crocodyliforms are very scarce in the Maastrichtian marine basins of Africa which are dominated by mosasaurid squamates. The latter became extinct by the KT boundary, while crocodyliforms survived and diversified in the Paleocene. Mosasaurids and crocodyliforms both lived in probably comparable marine environments during the Maastrichtian. The selectivity of the KT boundary extinctions remains to be explained; since freshwater environments are known for having been less affected by the KT crisis than marine ones, a freshwater lifestyle of the juveniles, like in extant marine crocodiles and unlike the fully marine mosasaurs, could explain this difference with regard to survivorship.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".