Ontogeny of <i>Euphanerops longaevus</i> from the Upper Devonian Miguasha Fossil–Fish–Lagerstätte and comparison with the skeletogenesis of the sea lamprey <i>Petromyzon marinus</i>
Bibliographic record
Abstract
Ontogeny is of paramount importance to understand evolutionary relationships of organisms. However, in the fossil record, early developmental stages are rarely preserved because of their unmineralized skeleton. Here, we describe the ontogeny of the Devonian jawless fish, Euphanerops longaevus, based on observations from more than 3500 specimens. The ontogeny of Euphanerops is compared with the development of the median fins of the extant jawless fish, the sea lamprey ( Petromyzon marinus). From a subsample of 216 specimens of Euphanerops, we define three ontogenetic stages: larvae (2–38 mm total length (TL), mostly composed of “ Scaumenella mesacanthi”), juveniles (28–98 mm TL), and adults (≥90 mm TL) based on the degree of skeletal development, chemical and microscopic compositions. Larvae display three cranial plates, a simple branchial apparatus, notochordal elements, and caudal fin supports. In juveniles, we document the development of paired anteroventral, anal, and median dorsal fins. Given how little information is generally available on ostracoderm ontogeny, the growth series of Euphanerops provides an unparalleled opportunity to understand the development of early vertebrate characters.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| 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".