Earliest North American articulated freshwater acanthomorph fish (Teleostei: Percopsiformes) from Upper Cretaceous deposits of Alberta, Canada
Bibliographic record
Abstract
Abstract Fossil material from the Maastrichtian part of the Scollard Formation is identified as belonging to an acanthomorph fish. An articulated specimen, preserved in part and counterpart, is a member of the paracanthopterygian order Percopsiformes, based on it having a full neural spine on the second preural centrum and two epurals in the caudal skeleton (both paracanthopterygian characters), as well as six branchiostegal rays and an anterodorsal excavated margin on the opercle (percopsiform characters). We name this as a new genus and species,Lindoeichthys albertensis. A phylogenetic analysis with no prior constraints recovered a single most-parsimonious tree with the new taxon placed as the sister group to a clade containing the Palaeocene Montana genusMcconichthys+ Percopsidae. However, this analysis did not recover the traditional percopsiforms (including Aphredoderidae and Amblyopsidae) as monophyletic. A second analysis, in which we constrained the traditional members of the Percopsiformes to be monophyletic, resulted in the new species being placed as the sister group toPercopsis. The articulated percopsiform specimen from the Pisces Point locality allows isolated dentaries from vertebrate microfossil localities to be identified as being from a member of that group. These isolated elements first appear in the late Campanian Judith River Group of Alberta and the Kaiparowits Formation of Utah, documenting that percopsiform fishes were present in the Western Interior of North America at least 75 Ma ago.
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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 | 0.003 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".