Anatomy of the Critically‐Endangered Anji Salamander ( <i>Hynobius amjiensis</i> ) Provides New Insights Into Morphological Evolution of Salamanders
Bibliographic record
Abstract
The Anji Salamander (Hynobius amjiensis) is a critically-endangered amphibian endemic to the Tianmushan Mountain area in southeastern China. As most of its congeneric species in the ancestral salamander family Hynobiidae, the osteology of H. amjiensis has remained essentially unknown and has hampered efforts in understanding morphological evolutionary patterns of early salamanders. Here, we investigate the skeletal anatomy of H. amjiensis based on microcomputed tomography scans of post-metamorphosed juvenile and adult specimens. Our results reveal Hynobiidae has more early-tetrapod-like plesiomorphic characters than expected, as H. amjiensis has a stapedial foramen in the middle ear and two centralia and a centrale-radius contact in the limb. We demonstrate that Hynobius amjiensis is the first known living salamander species with a stapedial foramen whose absence was believed to unite salamanders and anurans, and hence opens major questions on the evolution of the middle ear in modern amphibians: if some salamanders and caecilians had a stapedial foramen inherited from their common ancestor, when and how many times was the foramen lost independently in modern amphibians, and how did this structural loss impact the phylogenetic evolution of salamander clades? Our findings of hyper-ossified pectoral and pelvic girdles and loss of postminimus in the pes in H. amjiensis demonstrate that functional morphological features in hynobiids are potentially informative in phylogeny and ontogeny of early salamanders.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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) | 0.000 | 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 teacher head, 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".