On the origin of euphyllophyte roots: hypotheses from an Early Devonian <i>Psilophyton</i>
Bibliographic record
Abstract
BACKGROUND AND AIMS: Rooting structures have been documented in different Early Devonian plants, including rhyniophytes and zosterophylls. However, the basal euphyllophytes, the plexus from which modern ferns, equisetophytes and seed plants evolved, are the only group with no known rooting structures in Early Devonian representatives. We revisit the early euphyllophyte Psilophyton crenulatum, whose emergences have implications for rooting structure evolution within the clade. METHODS: Well preserved Early Devonian (earliest Emsian) material from the Val d'Amour Formation in New Brunswick (Canada) was freed from the rock matrix using acid. Over 2000 emergences from 28 randomly selected P. crenulatum axes were characterized qualitatively and quantitatively in terms of morphology and distribution. KEY RESULTS: The features of the emergences are more consistent with a rooting function than with any other possible role: irregular morphology, including forms with complex branching; anatomy involving external layers of thin-walled cells; apical meristematic growth that allowed for branching; terminations in filiform rhizoid-sized tips; and vertically polarized distribution, with nearly twice as many emergences on the lower sides of axes compared with the upper sides. The absence of any other potential rooting structures associated with P. crenulatum also supports a rooting function for the emergences. CONCLUSIONS: If the emergences of P. crenulatum had a rooting function, they are the oldest euphyllophyte rooting structures. They are also a novel, sui generis type of such structures among Early Devonian plants. They also provide the oldest direct evidence for gravity-induced morphological features in euphyllophytes. If they evolved from emergences like those of P. crenulatum, then euphyllophyte roots probably inherited from them apical growth and branching, and gene networks responsible for production of tip-growing filamentous cells. Progressive increase in size of such emergences could have increased auxin fluxes, leading to specification of vascular connections to subtending axes.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".