Possible dickinsoniomorphs from the latest Ediacaran Nama Group, southern Namibia
Bibliographic record
Abstract
The late Neoproterozoic Ediacaran Period is marked by one or more pulses of biotic turnover thought to represent intervals of global extinction, and which removed several enigmatic groups of Precambrian metazoans over a ∼10-million-year interval in the lead-up to the Cambrian. Here, we report the discovery of putative dickinsoniomorph ‘survivors’ from the Nama Group of southern Namibia, including specimens preserved in place directly above an ash bed dated in this study at 538.97 ± 0.21 Ma, and thus within error of the currently defined Ediacaran-Cambrian boundary. Some key features are poorly preserved and thus identification at this point is not definitive; however, following comparisons with a wide variety of other Ediacaran taxa and abiotic structures, we argue that interpretation as dickinsonimorph body fossils is most parsimonious. More material is undoubtedly required; however, if supported these fossils would represent the youngest dickinsoniomorph fossils found anywhere in the world, showing that this group survived the first pulse of Ediacaran extinction at ∼550 Ma, and necessitating a re-evaluation of hypothesized drivers of late Ediacaran biotic turnover events. We suggest that these new fossil discoveries are consistent with recent models of selective extinction driven by pulses of ecological stress, reinforcing the inference that environmental perturbations were likely a crucial influence on patterns of early animal evolution prior to the main phase of the Cambrian explosion.
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".