A new Antarctic heterobranch clade is sister to all other Cephalaspidea (Mollusca: Gastropoda)
Bibliographic record
Abstract
For a long time, Diaphanidae has been considered a basal family within Cephalaspidea, based on the presence of plesiomorphic morphological features within this taxon. Traditionally, the family contained the genera Bogasonia , Colobocephalus , Colpodaspis , Diaphana , Newnesia , Toledonia and Woodbridgea . Some phylogenetic analyses of several of these genera support the basal position of Diaphanidae within Cephalaspidea sensu stricto . However, the family is presently confirmed to be a polyphyletic taxon in which only the genus Diaphana is included. Several genera previously embraced within the family, such as the monotypic Newnesia , have never been previously analysed in molecular studies. Here, we provide an extensive morphological, anatomical and histological description of a new species of Newnesia from Antarctic deep waters (967–1227 m depth) in the Drake Passage. We also discuss the similarities to the traditional Diaphanidae genera to try to shed light into this phylogenetic conundrum. We sequenced cytochrome c oxidase subunit I, 16S rRNA , 28S rRNA and histone H3 markers of Newnesia antarctica and Newnesia joani n. sp. We analysed a comprehensive dataset of sequenced genera to evaluate the placement of both Newnesia species within the cephalaspidean families. Maximum‐likelihood and Bayesian phylograms support the monophyly of N. joani n. sp. and suggest cryptic speciation in N. antarctica specimens. Newnesia is recovered as the most basal offshoot of Cephalaspidea, suggesting the establishment of a new family restricted to Antarctic waters, named Newnesiidae n. fam., to hold both species. The possible Antarctic origin of Cephalaspidea is discussed.
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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 | 0.001 |
| 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".