Fortified Frogs and Skeletogenesis in the Skin: Osteoderm Development and Structure Across Tetrapods
Bibliographic record
Abstract
Skeletal organs reinforce the skin of many vertebrates. For most tetrapods these organs are osteoderms, bone‐rich inclusions of the dermis. Although common to armadillos and various reptilian groups, osteoderms have also been reported in frogs. Here we investigate and compare the structure and development of osteoderms across tetrapods, including new data from the study of two distantly related groups of frog, neotropical tree frogs (phyllomedusines) and Asian leaf litter frogs (megophyrids). Within each group, osteoderms demonstrate an inconsistent taxonomic distribution. Similar to other osteoderm‐bearing species, frog osteoderms are one of the last skeletal elements to form and exhibit asynchronous development across the body. Osteoderms first mineralize over the head and pectoral region, before appearing in more caudal and lateral positions across the body. Skeletogenesis is initiated within the dermis at the interface between the superficial and deep layers. Whereas all skeletally mature osteoderms demonstrate a heterogeneous tissue composition, including lamellar‐fibred and woven‐fibred bone, the organization of these tissues often differs between species. Unique to some frogs, the dermis is occupied by a second skeletal organ. This calcified, glycosaminoglycan‐rich tissue, known as the Eberth‐Kastschenko layer (= EK layer; lamina calcarea), is histologically distinct from bone and may instead represent a dental tissue. Our data reveals strong developmental and structural similarities among all tetrapod osteoderms, and highlights the latent skeletogenic capacity of the dermis. Support or Funding Information Natural Sciences and Engineering Research Council of Canada (NSERC) 400358
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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".