Two exceptionally preserved biotas from North Dakota reveal cryptic Ordovician shelf ecologies
Bibliographic record
Abstract
The Ordovician saw one of the greatest evolutionary radiations in the Earth’s history, precipitating the assembly of modern animal-dominated ecologies in the aftermath of the Cambrian Explosion. However, Ordovician nonmineralized faunas are rare and mostly sample ecologically marginal settings. We describe small carbonaceous fossils (SCFs), including semiarticulated elements preserving submicrometric detail, from epicratonic deposits of the Deadwood and Winnipeg formations (ND). The Osterberg SCFs, associated with biostratigraphically informative conodonts and graptolites, record two successive biotas of Cambrian-Tremadocian (the “lower Osterberg” biota) and Darriwilian (the “upper Osterberg” biota) ages, demonstrating a long-term persistence of high-quality, Burgess Shale-type microfossil preservation after the end of the Cambrian. Their components open a window on normal marine, well-oxygenated Ordovician shelf habitats, revealing taxa and functional morphologies unrecorded by coeval macrofossils. These include specialized grazing and predatory molluskan radulae, triturative crustaceomorph molars, the oldest known eurypterid-type cuticles, and microphagous priapulid worms. The Osterberg fossils attest to an Ordovician co-occurrence of cryptic taxa and feeding adaptations, reminiscent of the most ecologically modern Cambrian biotas, alongside classic later-Paleozoic forms like colonial zooplankton and biomineralized early vertebrates. By contrast, they do not record classic Burgess Shale-style taxa typical of marginal or deeper-water Ordovician assemblages. These results demonstrate a lasting presence of cryptic, modern-style shelf faunas throughout the earliest Paleozoic, suggesting that exceptional Ordovician macrofossil sites are unrepresentative of the broader state of their coeval biosphere.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.000 |
| 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 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".