Digital volumetric modeling reveals unique body plan experimentation in the Devonian tetrapod Ichthyostega
Bibliographic record
Abstract
The water-to-land transition in tetrapods promoted a radical shift in locomotor function and kinematic patterns, from axial- to appendicular-dominated propulsion and from buoyancy- to musculoskeletal-driven support. Many of these facets of locomotion are dictated by an animal's whole-body mass properties, which presumably also changed across this transition. We herein use digital volumetric modeling to reconstruct mass properties in the Late Devonian tetrapod Ichthyostega . In comparison to fishes and crown tetrapods, our results show that Ichthyostega possessed a uniquely "robust" body plan, combining traits typical of both "fishes" (anterior center-of-mass) and "tetrapods" (well-developed limbs, especially forelimbs). We also find that variation in body composition has little effect on body attitude at flotational equilibrium, suggesting that whole-body "evolutionary tinkering" had little impact on hydrostatic profile. These results support previous inferences of forelimb-dominated movements in Ichthyostega and highlight a hitherto underappreciated level of morphological experimentation during the tetrapod transition to land.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| 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".