Morphology and systematic position of <i>Shaninopsis</i> Isberg, 1934 (Bivalvia: Cryptodonta), from the Boda Limestone (Upper Ordovician), Sweden
Bibliographic record
Abstract
ABSTRACT In a classic study of bivalves from the Upper Ordovician (Katian) Boda Limestone, Sweden, Isberg (1934) named and described 18 species of the unusual bivalve Shaninopsis, all from the same locality. Our study of the type material indicates that only three species at most are present: Shaninopsis prona Isberg, 1934, Shaninopsis radiata Isberg, 1934, and an unnamed species. Shaninopsis features a thick, prosocline, tear-drop-shaped shell with an opisthogyrous larval shell. Anterodorsally, the shell outline appears truncated to strongly concave owing to an inset sical surface that frames a conspicuous pedal gape. Above the gape, the lunule accreted posteriorly (retrusive growth—new term) and abuts the anterior part of the ligament area, perhaps compensating for anterior splitting of the ligament during growth. The hinge plate is edentulous, with a broad, opisthodetic, monovincular ligament. Muscle scars visible include only the posterior adductor, which is set near the posteroventral shell margin. Relict calcite prismatic texture preserved on the ligament area indicates the external prismatic calcite shell layer underlaid the ligament as in cardiolid praecardioids and some inoceramiformians. Evidence for a retractable non-biomineralized sheath-like structure extending from the pedal gape is presented. Shaninopsis is reconstructed as an orthothetic, epifaunal or shallow semi-infaunal bivalve capable of deeply probing underlying sediment for H2S uptake for chemosynthesis. Shaninopsis is assigned to a new subfamily Shaninopsiinae in the family Lunulacardiidae (infraclass Cryptodonta), a group otherwise unknown in pre-upper Silurian rocks. Remarkable similarities of Shaninopsis with the Permian bivalve Eurydesma suggest a mutual though geochronologically distant phylogenetic relationship.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| 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".