An enigmatic braincase from Five Points, Ohio (Westphalian D) further supports a stem tetrapod position for aïstopods
Bibliographic record
Abstract
ABSTRACT We describe a new specimen of the aïstopodOestocephalusfrom Five Points, Ohio, which preserves much of the posterior braincase. The specimen, the largest aïstopod skull described, preserves the postorbital region to the occiput. The posterior braincase has coossified the basioccipital, exoccipitals, and opisthotic. The parasphenoid is rostrally restricted, toothless, and highly vaulted along the cultriform process. The lateral walls of the cultriform process are further reinforced by large longitudinally running, ventral flanges from the parietals. Two large endochondral ventral projections from the basioccipital, previously interpreted as basal tuberosities for hypaxial muscle insertion, are here instead interpreted as articulations for the branchial skeleton. This interpretation is further supported by traces of vasculature that is consistent with what is seen in gill-bearing species. A model for the reorganisation of the basicranial region on the transition from hyomandibula to stapes is proposed, which suggests that gills, or gill-support skeletal elements, might be further distributed along the tetrapod stem than previously thought. These data further support the placement of aïstopods in the tetrapod stem group and require a reconsideration of our understanding of early tetrapod evolution.
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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 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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".