Unexpected ubiquity of heart‐shaped scale morphotype in Centroplasthelida (Haptista): Ancestral trait or multiple acquisitions?
Bibliographic record
Abstract
Centrohelids (Haptista: Centroplasthelida) are axopodial protists with a remarkable diversity of external siliceous scale morphologies. It is believed that the last common ancestor of centrohelids had a double layer of siliceous scales composed of plate scales closer to a cell surface and spine scales radiating outwards. The characteristic morphotype of spine scales with a heart-shaped base was once believed to be a unique feature of the genus Choanocystis, as it was defined by Siemensma and Roijackers (1988). Further research revealed that this morphology is present in different and sometimes distantly related lineages: Ozanamiidae, Meringosphaeridae, and Marophryidae. Here, we report the fourth clade, Pterocystidae, which is also revealed to contain representatives having this phenotype. Cernunnos gen. nov. is erected here to place Cernunnos uralica sp. nov., Cernunnos arctica sp. nov., Cernunnos america sp. nov., and Cernunnos antarctica Tikhonenkov et Mylnikov, 2010, Gerasimova comb. nov. C. uralica was studied with scanning electron microscopy and SSU rDNA sequencing. Molecular phylogenetic analysis placed it into marine environmental clade P within Pterocystida. The ubiquity of spine scales with heart-shaped bases could be an example of parallel evolution, but taking into account the considerable similarity it is likely an ancestral trait, acquired from the last common ancestor of centrohelids.
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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 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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".