Phylogenetic Position of Xenoturbella bocki and Hemichordates Balanoglossus carnosus and Saccoglossus kowalevskii Based on Amino Acid Composition or Nucleotide Content of Complete Mitochondrial Genomes
Bibliographic record
Abstract
To clarify the phylogenetic position of Xenoturbella bocki and hemichordates (Balanoglossus carnosus and Saccoglossus kowalevskii), which occupy an ambiguous evolutionary position between vertebrates and invertebrates, we expanded a pre-existing baseline vertebrate data set by incorporating randomly selected invertebrates. Based on nucleotide content calculated from complete mitochondrial genomes, invertebrates were classified into two groups, high C/G and low C/G, with vertebrates placed within the high-C/G invertebrate group. X. bocki and hemichordates (B. carnosus and S. kowalevskii) also fell into the high-C/G invertebrate group. We also analyzed amino acid composition and nucleotide content of complete mitochondrial genomes or 16S rRNA genes using Ward’s clustering method and neighbor-joining. In the resulting phylogenetic trees, invertebrates are classified into high C/G and low C/G categories, and vertebrates are divided into terrestrial and aquatic groups. In addition, X. bocki and representative hemichordates B. carnosus and S. kowalevskii appear to be more closely related to vertebrates than to invertebrates.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".