<i>Arcellites punctatus</i> sp. nov.: a new megaspore from the Early Cretaceous of Portugal studied using high resolution synchrotron radiation X-ray tomographic microscopy (SRXTM)
Bibliographic record
Abstract
A new species of megaspores, Arcellites punctatus sp. nov. and associated microspores, are described from the Early Cretaceous Torres Vedras, Catefica and Buarcos localities in Portugal. The new taxon is most abundant in the Torres Vedras plant assemblages where it co-occurs with several other types of megaspores, remains of aquatic and terrestrial angiosperms as well as other plant fossils. The megaspore body is smooth without appendages, finely perforated and with a rugose surface pattern. High resolution synchrotron radiation X-ray tomographic microscopy (SRXTM) analysis of the megaspore wall shows a three-layered structure. The outer layer is punctate-perforate. Perforations are densely spaced in the valleys between the ridges, while they are more scattered or lacking on the top of the ridges. The middle layer is granular-fibrous and of uneven thickness causing the rugose surface pattern. The inner layer is evenly thin and solid. The outer layer of the megaspore body continues into the elongated, six-parted and inverted cone-shaped acrolamella or neck. Lateral margins of acrolamella segments are laminar and crenulate. Microspores occur attached to the acrolamella of all specimens studied in scanning electon microscopy (SEM) and SRXTM. In general morphology, the megaspores are closely similar to megaspores of Arcellites rugosus from Canada that also lack body appendages, but the Portuguese megaspores are distinguished by their distinct punctate-perforate megaspore wall structure.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".