<i>Polypterus</i> and the evolution of fish pectoral musculature
Bibliographic record
Abstract
Polypterus, a member of the most primitive living group of ray-finned fishes, has demonstrated the ability to perform fin-assisted terrestrial locomotion, a behavior that indicates a complex pectoral musculoskeletal system. Review of the literature reveals that many aspects of the pectoral muscular anatomy of Polypterus are still unclear, with a number of conflicting descriptions. We provide a new interpretation of the pectoral musculature using soft tissue-enhanced microCT scanning and gross anatomical dissection. The results demonstrate a complex musculature, with six independent muscles crossing the glenoid-fin joint. Comparisons with other bony-fish (Osteichthyes), including both ray-finned (Actinopterygii) and lobed-fin (Sarcopterygii) fish, indicate the presence of novel muscles within Polypterus: coracometapterygialis I+II and the zonopropterygialis medialis. Examination of these muscular additions in the context of osteichthyan phylogeny indicates that this represents a previously unrecognized event in the evolution of pectoral musculature in Osteichthyes. Despite its phylogenetic position as a basal actinopterygian, the musculature of Polypterus has more similarities both anatomically and functionally with that of sarcopterygians. This anatomy, along with other features of Polypterus anatomy such as lobed fins, ventral paired lungs, and a large spiracle, may make it a good model for inferences of stem tetrapod locomotion.
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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 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.001 | 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".