<i>Paucicanthus vanelsti</i>gen. et sp. nov., an Early Devonian (Lochkovian) acanthodian that lacks paired fin-spines
Bibliographic record
Abstract
The acanthodian Paucicanthus vanelsti gen. et sp. nov. is described from six body fossils from Lower Devonian (Lochkovian) rocks of the southern Mackenzie Mountains, Northwest Territories, Canada. This new species is unique among acanthodians in that it lacks both pectoral and pelvic fin-spines. In the absence of fin-spines, the leading edges of the pectoral and pelvic fins are reinforced by enlarged scales. The anatomy of the acanthodiform Traquairichthys pygmaeus is similar to P. vanelsti in that both lack pelvic fin-spines, although T. pygmaeus also lacks pelvic fins. Similarly, the acanthodian Yealepis douglasi lacks both paired and median fin-spines, and its anatomy resembles that of P. vanelsti based only on the loss of paired fin-spines. The lack of paired and (or) median fin-spines in these three taxa contrasts with the widely held view that acanthodian fins all were preceded by spines. The anatomy of P. vanelsti also is similar to that of the acanthodian Brochoadmones milesi in that both have a completely unossified endoskeleton, slightly elevated pectoral fins, and deep, compressed bodies. The median fin-spines of P. vanelsti have an anterior leading edge rib followed by a field of fine striations. This striated ornamentation coupled with few leading edge ribs also is seen on fin-spines of Cassidiceps vermiculatus and primitive acanthodiform acanthodians (e.g., Mesacanthus and Lodeacanthus species). I tentatively suggest that this fin-spine ornament indicates relationship between P. vanelsti, acanthodiform acanthodians, and C. vermiculatus. However, a cladistic analysis is required to test whether or not the characteristics such as fin-spine loss, unossified endoskeleton, elevated pectoral fins, deep compressed bodies, and (or) median fin-spine ornamentation are synapomorphies within the Acanthodii or evolved convergently within the class.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".