Extant cartilaginous fishes share trabecular and areolar mineralization patterns, but not tesserae, and evidence for a paedomorphic chimaera skeleton
Bibliographic record
Abstract
Abstract A comprehensive study is lacking that clearly defines and directly compares the diverse mineralized endoskeletal tissues exhibited by extant chondrichthyans (elasmobranchs, such as sharks and skates, and holocephalans, such as chimaeras). Tiles of mineralized polygonal structures called tesserae occur at cartilage surfaces in chondrichthyans, but recent studies showing trabecular structures suggest that tesserae are not as common as previously thought. A specific region of tesserae termed cap zone and continuous (not tiled) mineralized elasmobranch neural arches demonstrate bone-like tissues. Areolar mineralized tissue in elasmobranchs is generally considered a unique chondrichthyan feature. Despite these reports, it remains unclear what mineralized endoskeletal features define extant chondrichthyans. To address this question, adult skeletal tissues in two elasmobranchs (little skate and small-spotted catshark) and a chimaera (spotted ratfish) were characterized using synchrotron radiation and desktop micro-CT imaging, and histological and immunofluorescent assays. Data from these extant chondrichthyan representatives suggested that trabecular and areolar mineralization, but not tesserae and bone-like tissues, are shared features of the extant chondrichthyan endoskeleton. Interestingly, three separate analyses argued that the chimaera endoskeleton retains ancestral embryonic features (i.e., paedomorphic). This study further proposes general terminology for character states of the extant chondrichthyan endoskeleton and infers those states in ancestral chondrichthyans.
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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 | 0.000 |
| 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".