The morphology of the terminal phalanges in Permo-Carboniferous synapsids: an evolutionary perspective
Bibliographic record
Abstract
Morphological features of the terminal phalanges of extinct tetrapods can be used to infer whether or not keratinous claws were present even though these structures are not preserved in the fossil record. Such features as dense vascularization grooves and foramina, and a general claw-like morphology, are present in some of the earliest fully terrestrial tetrapods, the Permo-Carboniferous synapsids. Early synapsids are represented by a rich fossil record that preserves the detailed anatomy of the terminal phalanges and allows for an examination of the early evolution of these structures in a well-resolved phylogenetic context. The pattern of change in the morphology of the terminal phalanges of five basal synapsids, Cotylorhynchus romeri, Varanops sp., Edaphosaurus boanerges, Haptodus garnettensis, and Dimetrodon limbatus, reveals a clear trend from a broad, flat, and spatulate morphology in the basal taxa to a tall, narrow, and curved structure. This trend in overall shape change does not reflect changes in feeding behaviour. The size and shape of the flexor tubercle appears to be a factor of size and function, rather than possessing a phylogenetically informative signal. The osteological features used to infer the presence of a keratinous sheath in the synapsids are also observed in the non-amniote taxon Diadectes absitus. This indicates that claws were not an amniote innovation and that they instead originated somewhere outside the crown group Amniota.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".