A New Species of<i>Pityostrobus</i>from the Lower Cretaceous of California and Its Bearing on the Evolution of Pinaceae
Bibliographic record
Abstract
A single cylindrical, abraded cone specimen has been found associated with ammonites of the Lower Cretaceous Budden Canyon Formation near Ono, California. The specimen was embedded in bioplastic and sectioned using the cellulose acetate peel technique. The pith is composed of parenchyma and scattered sclereids and is bounded by a ring of resin canals. The secondary xylem of the cone axis, with a ring of small‐diameter resin canals, is continuous. The cortex is composed primarily of parenchyma with an outer sclerotic zone 10–16 cells thick and has 27–30 dilating resin canals. Vascular traces to the ovuliferous scale and bract diverge separately from the vascular cylinder and are accompanied by a single resin canal from the pith that is positioned between the arms of the horseshoe‐shaped ovuliferous scale trace. The bract trace is terete, accompanied by two lateral resin canals from the cortical axial system, and enters the free part of the bract. The ovuliferous scale is almost completely sclerotic, with resin canals both abaxial and adaxial to the vascular strands. A large interseminal ridge is present between the two winged seeds on each scale. This cone represents a new species of Pityostrobus and is described as Pityostrobus californiensis sp. nov. A phylogenetic analysis using morphological data from the ovulate cones of all the extant and fossil taxa of Pinaceae, as well as those of Cryptomeria japonica, Sciadopitys verticillata, and Pararaucaria patagonica, was done. Relationships of the fossil species of Pityostrobus, Obirastrobus, and Pseudoaraucaria to the living taxa of Pinaceae were assessed. The idea that Pityostrobus represents an artificial assemblage of pinaceous taxa is supported by the analyses. The genus Obirastrobus cannot be distinguished from Pityostrobus species, while Pseudoaraucaria species appear as a clade. The difficulty of basing fossil taxa purely on cone characteristics is discussed in light of the analyses.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".