Reassessment of the late Campanian (Late Cretaceous) heteromorph ammonite fauna from Hornby Island, British Columbia, with implications for the taxonomy of the Diplomoceratidae and Nostoceratidae
Bibliographic record
Abstract
Three heteromorph ammonite families are represented within upper Campanian (Upper Cretaceous) strata of the Northumberland Formation exposed on Hornby Island, British Columbia: Baculitidae, Diplomoceratidae and Nostoceratidae. A variety of species are distinguished within these families, of which only three taxa – Baculites occidentalis Meek, 1862, Diplomoceras (Diplomoceras) cylindraceum (Defrance, 1816) and Nostoceras (Nostoceras) hornbyense (Whiteaves, 1895) – have been reported previously. Over the last decade, large new collections and the further preparation of existing collections has provided new taxonomic and morphometric data for the Hornby Island ammonite fauna, from which new descriptions of heteromorph taxa are formulated. Eleven taxa are recognized, including the new species Exiteloceras (Exiteloceras) densicostatum sp. nov., Nostoceras (Didymoceras?) adrotans sp. nov. and Solenoceras exornatus sp. nov. Morphometric analyses of over 700 specimens demonstrate the considerable phenotypic plasticity of these ammonites, which exhibit a broad spectrum of variability in their ornamentation and shell dimensions. A large population sample of Nostoceras (Nostoceras) hornbyense provides an excellent case study of a member of the Nostoceratidae; the recovery of nearly complete, well-preserved specimens enables the re-evaluation of diagnostic traits within the genus Nostoceras. The north-east Pacific Nostoceras (Nostoceras) hornbyense Zone and the global Nostoceras (Nostoceras) hyatti Assemblage Zone are here regarded as correlative, reinforcing a late Campanian age for the Northumberland Formation. http://zoobank.org/urn:lsid:zoobank.org:pub:EEF7416A-3AC7-47CC-8667-806F6A7FE567
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".