A new species of osteostracan from the Lochkovian (Early Devonian) of the Mackenzie Mountains, with comments on body size, growth, and geographic distribution in the genus <i>Machairaspis</i>
Bibliographic record
Abstract
Machairaspis, a genus of the Osteostraci, an extinct clade of jawless vertebrates, has been reported from localities in Spitsbergen, Norway, Podolia (Ukraine), and Prince of Wales Island (Nunavut, Canada). A new species of Machairaspis, described here from the Delorme Formation at the MOTH locality, extends the geographic range of this genus to the Mackenzie Mountains. Machairaspis serrata sp. nov. is known from a very small headshield and a fragment of an even smaller individual. The two specimens share distinctive, dorsally pointed serrations on the posterior margin of the exceptionally tall dorsal spine of the headshield. The new species can also be differentiated from other species of Machairaspis by characteristic rows of denticles along the margin of the headshield and is represented by much smaller individuals than are known for previously described species in the genus. Differences in the proportions of the cephalic spine illustrate allometric increase in relative spine height during growth, as previously documented for the related genus Superciliaspis. Machairaspis is here included with Scolenaspis in the subfamily Scolenaspidinae, sister to the subfamily Zenaspidinae in the family Zenaspididae. The presence of Machairaspis at MOTH is an additional similarity with Early Devonian fauna of Spitsbergen and is consistent with the Lochkovian (Early Devonian) age that has been proposed previously for the MOTH locality and with the suggestion that Spitsbergen represents part of the Laurentia terrane.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".