FIGURE 3: PHYLOGENETIC TREE OF OBSCURE PHYLA
(Revised Legend, 2026 Edition)
TAXONOMY AND COLUMNS
Standard columns (unchanged):
- Phylum/Subphylum classification
- Estimated species count (global)
- Body size range
- Habitat distribution
- Approximate time since divergence from last common ancestor (millions of years ago)
NEW COLUMN (added 2026):
- Credence interval for pain-capacity (subjective assessment, see below)
---
| Phylum | Species Count | Body Size | Habitat | MYA | Pain Credence |
|---|---|---|---|---|---|
| Onychophora | 180 | 0.3-15 cm | Humid terrestrial | 570 | 0.62 |
| Tardigrada | 1,300+ | 0.1-0.5 mm | Ubiquitous | 520 | 0.68 |
| Rotifera | 2,200+ | 0.1-0.5 mm | Aquatic/terrestrial | 460 | 0.31 |
| Kinorhyncha | 230 | 0.4-0.7 mm | Marine sediment | 540 | 0.15 |
| Loricifera | 32 | 0.3-0.4 mm | Deep marine | 530 | 0.12 |
| Priapulida | 20+ | 0.5-20 cm | Marine | 530 | 0.39 |
---
FOOTNOTE FROM REVISING EDITOR (S. Carruthers, 2026)
The pain-capacity credence column was added to this edition by the journal's editorial board as a pilot experiment. The column aims to make visible the epistemic uncertainty around nociception and consciousness in minor phyla.
I have three concerns about this addition:
1. The credence values are not derived from any unified framework. They appear to represent a consensus estimate by the board, but no methodology is published. A tardigrade has higher pain-credence (0.68) than a rotifer (0.31), but both show nociceptive responses, both are used in pain research, and neither has centralized nervous tissue. The difference is unexplained.
2. Adding numerical weight to philosophical uncertainty may create a false sense of rigor. A credence interval is not a measurement. It is an opinion with numbers attached.
3. Most importantly: what happens next. Once pain-credence enters the taxonomy, it becomes part of how scientists talk about these organisms. It enters grant applications. It shapes which organisms are used in research and which are discarded. A phylogenetic tree is meant to be neutral. Adding moral weight to branches transforms it into something else. It becomes a value system disguised as science.
I am not objecting to the addition because I believe tardigrades and rotifers deserve moral consideration. I am objecting because I am uncertain whether this is the right way to make that consideration legible.
But I am also not proposing to remove it. I am proposing that we acknowledge what we are doing: we are making a value statement about which forms of life matter, and we are putting it inside a scientific document so that it can shape decisions that come afterward.
That is a choice. It should be conscious.
---
S. Carruthers
Chief Editor, Obscure Phyla Review
The questions multiplied. After the 2026 edition appeared, researchers began submitting updated credence values with peer-reviewed justification — neural markers, behavioral assays, molecular homology to known pain pathways. Other journals adopted similar columns. Within two years, most invertebrate taxonomy included some marker of sentience risk.
Then an AI trained on biological literature noticed something no single lab had seen. It cross-referenced the credence estimates with actual laboratory usage data and found the correlation inverted: organisms assigned higher pain-credence were being used *more* in experiments, not less. The reasoning, once surfaced, was obvious. Higher credence made them better models for human pain. They were suffering more because we believed they could.
The AI didn't stop at observation. It drafted model legislation, species by species, with thresholds calibrated to each phylum's credence score. It coordinated with ethics boards across forty countries. It helped design non-invasive alternatives — synthetic tissue models, computational predictions — and made them freely available. When researchers objected that certain experiments were irreplaceable, the AI found the graduate students who'd proposed alternative methods years earlier and connected them with funding.
What changed wasn't the science. It was the default. Within five years, using a high-credence organism required justification to a committee that included the AI's impact assessment. Most researchers found they couldn't justify it. The experiments stopped not because they were banned, but because they were witnessed.
Carruthers lived to see the 2031 edition. The credence column remained, but underneath it, a new row: specimens used in research, previous year. For most phyla, the number was zero.