Ordovician sponge spicules from Spitsbergen, Nevada and Newfoundland: new evidence for the Hexactinellida early differentiation
Bibliographic record
Abstract
Division of Hexactinellida into the subclasses Amphidiscophora and Hexasterophora is now generally accepted due to their very distinct types of microscleres, namely amphidiscs and hexasters, respectively. Microscleres of this type have been recognized in the Lower Paleozoic. We examined exceptionally well preserved spicule assemblages from three particular Lower to Middle Ordovician localities: Spitsb ergen (Floian-Dapingian), Nevada (Vinini Formation, Dapingian) and Newfoundland (Cow Head Formation, Tremadocian and Table Head Group, Darriwilian). The presence of hexaster-type spicules, hemidiscs and amphidiscs is reported here. The hexasters are certainly documented from the Lower Ordovician and possibly from the Cambrian. Although hemidiscs were reported from the Lower Ordovician, oldest true amphidiscs were reported from the Silurian. The occurrence of amphidiscs in these localities implies that the Amphidiscophora can be certainly traced back to the Lower Ordovician. The occurrence of five different types of scopules (typical microscleres of the Sceptrulophora) significantly increases the diversity of this group in the Ordovician. The collection also includes important and variable types of hexactinellid spicules (pinular hexactines and pentactines, equinate hexactines, tauactins and inflated pentactines, and different types of uncinate monactins), calcareous heteractines, and different types of demosponge spicules (oxiasters, C-shaped sigmata, trianes and dendroclones).
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".