Elasmobranchs from the Lower Triassic Sulphur Mountain Formation near Wapiti Lake (BC, Canada)
Bibliographic record
Abstract
Hybodontoid and nonhybodontoid sharks are described from the Lower Triassic Vega-Phroso Siltstone Member of Sulphur Mountain Formation on the basis of newly discovered material. The age of the classic fossil site ‘Wapiti Lake’ in the Canadian Rocky Mountains is discussed on the basis of new field data and one conodont found in association. Preliminary results suggest that these elasmobranch remains are between early Smithian and Spathian in age. Apart from the enigmatic genus Listracanthus and previously reported edestoids, the shark fauna consists of at least one hybodont, at least two questionable hybodontoid genera and an elasmobranch of enigmatic affinities, represented by peculiar denticles only and described as ‘genus A’ incertae sedis. The presence of the only previously reported hybodont genus, cf. Palaeobates, is erroneous. The largest specimen represents the most complete Early Mesozoic shark known. The heterodonty of its dentition, fin spine morphology and the short, robust body shape imply it represents a member of a new family of shark, Wapitiodidae fam. nov., and is described here as Wapitiodus aplopagus gen. et sp. nov. The unique dental morphology shows affinities to Polyacrodus but clearly differs in the complete lack of side cusps. Wapitiodus gen. nov. possesses a primitive fin spine structure. The tooth crowns are entirely blunt in the distal (posterior) tooth files, and are acuminate-unicuspid in several anterior files. Tooth morphology, the shape of the basal cartilages, the proximal insertion of the fin spines and the pectoral fin structure are interpreted as diagnostic characters for this new genus, and possibly for the Wapitiodidae fam. nov. The majority of observed characters appear to be primitive and are reminiscent of Palaeozoic sharks, however, and these features include dorsal fin spine morphology and gross skull anatomy. A second species, provisionally placed in the same genus, is described as Wapitiodus homalorhizo sp. nov. Wapitiodus homalorhizo sp. nov. can be distinguished from W. aplopagus gen. et sp. nov. by the proportions of the fin spines, tooth morphology and possibly the body shape. Several isolated teeth and other fragmentary material are referred to either Wapitiodus gen. nov. sp. indet. or to ?Polyacrodus sp. (Polyacrodontidae gen. et sp. indet.). A third genus of elasmobranch (incertae sedis) is described as ‘Genus A’ and is recognized by its peculiar scales.
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".