Examining competition during the agnathan/gnathostome transition using distance-based morphometrics
Bibliographic record
Abstract
Abstract The rise of jawed vertebrates (gnathostomes) and extinction of nearly all jawless vertebrates (agnathans) is one of the most important transitions in vertebrate evolution, but the causes are poorly understood. Competition between agnathans and gnathostomes during the Devonian period is the most commonly hypothesized cause; however, no formal attempts to test this hypothesis have been made. Generally, competition between species increases as morphological similarity increases; therefore, this study uses the largest to date morphometric comparison of Silurian and Devonian agnathan and gnathostome groups to determine which groups were most and least likely to have competed. Five agnathan groups (Anaspida, Heterostraci, Osteostraci, Thelodonti, and Furcacaudiformes) were compared with five gnathostome groups (Acanthodii, Actinopterygii, Chondrichthyes, Placodermi, and Sarcopterygii) including taxa from most major orders. Morphological dissimilarity was measured by Gower's dissimilarity coefficient, and the differences between agnathan and gnathostome body forms across early vertebrate morphospace were compared using principal coordinate analysis. Our results indicate competition between some agnathans and gnathostomes is plausible, but not all agnathan groups were similar to gnathostomes. Furcacaudiformes (fork-tailed thelodonts) are distinct from other early vertebrate groups and the least likely to have competed with other groups.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| 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 | 0.000 |
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".