Early Eudicot flower and fruit: Dakotanthus gen. nov. from the Cretaceous Dakota Formation of Kansas and Nebraska, USA
Bibliographic record
Abstract
Abstract An extinct plant that populated the eastern margin of the Cretaceous Midcontinental Seaway of North America about 100 million years ago has attracted interest as one of the earliest known bisexual flowers in the fossil record. Reexamination of the type specimen of Carpites cordiformis Lesq., and corresponding specimens from sandstones and clays of the Dakota Formation of Kansas and Nebraska and the correlative Woodbine Sandstone of Texas, with both light microscopy and micro CT scanning, leads to a revised concept of the morphology and affinities of the “Rose Creek flower”. The moderately large flowers (22–30 mm diameter) have two perianth whorls: five basally fused sepals and five free spatulate petals. The gynoecium is pentacarpellate with five styles. A crescent-shaped nectariferous pad occurs at the base of the gynoecium aligned with each sepal. Ten stamens are inserted at the level of the nectaries, one whorl organized opposite the sepals and another opposite the petals. In situ pollen is oblate, brevitricolporate and finely verrucate. The fruits are loculicidal capsules with persistent calyx and disk. Comparing the full suite of observed characters with those of extant angiosperms indicates particularly close similarity to the monogeneric fabalean family Quillajaceae, with shared features of perianth number and morphology, nectary position and morphology, stamen number and morphology, and gynoecium merosity, although the fossil differs from extant Quillaja in fruit type (capsule vs basally syncarpous follicles) and especially in pollen morphology (10 μm oblate, microverrucate, vs 30–40 μm prolate, striate).
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".