Taxonomy, morphology and phylogeny of Late Cretaceous spirulid coleoids (Cephalopoda) from Greenland and Canada
Bibliographic record
Abstract
Abstract: Groenlandibelus rosenkrantzifrom the Maastrichtian of Greenland has long been thought to constitute an early representative of spirulid coleoids. This study shows that this view must be reassessed, at least in part. A re‐investigation of the types and of material recorded subsequently has revealed that none of these specimens is conspecific with the holotype ofG. rosenkrantzi.Cyrtobelus birkelundaegen. nov, sp. nov. differs from the type ofG. rosenkrantziin having lower chambers and in lacking an apically elongated sheath. The longiconic phragmocone ofG. rosenkrantzihas more features in common with the presumed spirulid genusNaefia. A specimen described in detail by J. A. Jeletzky in the mid 1960s as ‘G. rosenkrantzi’ is designated holotype ofC. birkelundaesp. nov., which means that internal phragmocone features are still unknown inG. rosenkrantzi. Cyrtobelus hornbyensegen. nov, sp. nov. from the Campanian of western Canada constitutes the first record of early spirulids from the northeast Pacific, being based on seventeen extraordinarily well‐preserved phragmocones. This species differs fromC. birkelundaesp. nov. only in the width of the siphuncular tube. The presence of a caecum, a nacre‐less conotheca that represents the continuation of the protoconch conotheca, conothecal flaps that anchor the mural parts of the septa, and a thin investment‐like sheath are characters shared only with RecentSpirula.In particular, the unusual protoconch architecture ofCyrtobelusgen. nov. challenges a phylogenetic origin within bactritoid‐like coleoids.
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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 | 0.001 | 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".