Braincase of a polycotylid plesiosaur (Reptilia: Sauropterygia) from the Upper Cretaceous of Manitoba, Canada
Bibliographic record
Abstract
The braincase of a polycotylid plesiosaur referable to Dolichorhynchops from the Niobrara Formation (Santonian to the earliest Campanian) in Manitoba, Canada, is described. The well-preserved material without matrix permits observation of various anatomical features of the polycotylid braincase with unprecedented clarity. A virtual reconstruction of the braincase was created by using a three-dimensional scanning technique that produces accurate reconstruction of missing or damaged elements and demonstrates the three-dimensional relationships among the elements. Comparison with other plesiosaurian braincases revealed previously unrecognized characters and character states. The I-beam-shaped parasphenoid, the relatively short pituitary fossa, and the anterior process of the prootic are possible synapomorphies of the Polycotylidae or of its subclades. It could be a challenge to confirm the presence of the supraoccipital process and its median ridge, as well as the presence of the fenestra ovalis, in polycotylid skulls because of the location and orientation of these structures. Variable morphology of basioccipital-basisphenoid contact and the paroccipital process in Dolichorhynchops and related taxa require further investigation. The I-beam of the parasphenoid and the wide contact surfaces of the basioccipital and neighboring elements provide more resistance to flexion of the braincase. Distribution of the extensive pterygoid-basicranium contact, the shape of foramen magnum, anterior process of the prootic, and the short pituitary fossa do not confirm the current phylogenetic hypotheses. The location and orientation of the fenestra ovalis suggest the lack of a tympanic ear in this plesiosaur.
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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) | 0.001 | 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 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".