New Siluro-Devonian Anomalocystitids (Echinodermata, Stylophora) from Bolivia and Canada, and a Reevaluation of Skeletal Homologies in Mitrates
Bibliographic record
Abstract
Two new mitrate stylophorans are described from the upper part of the Santa Rosa Formation (Lochkovian) in the Central Subandean Zone of Bolivia and from the Jupiter Formation (Cybèle Member, late Llandovery) of Anticosti Island (Canada). Both stylophorans are identified as allanicytidiine anomalocystitids. The new Bolivian mitrate, Perikefalea racheboeufi gen. and sp. nov. is characterized by a strongly reduced number of plates (five) on its upper thecal surface and a strong spike on its posterior median marginal. The morphology of P. racheboeufi suggests relatively strong affinities with Occultocystis, from the Lower Devonian Talacasto Formation of Argentina. Although incompletely preserved, the Anticosti mitrate, Perikefalea? cybeleae sp. nov., represents the first stylophoran described in the Silurian of North America and the first report of post-Ordovician Allanicytidiinae outside of (peri) Gondwanan regions. Skeletal homologies in mitrates (marginals, infracentrals, posterior spines, adorals, supracentrals) are reevaluated, so as to describe the plate pattern of Perikefalea. This revision was prompted by new fossil evidence from the Furongian–Tremadocian interval suggesting that (1) mitrates derive from “Phyllocystis” jingxiensis-like cornutes with wide marginals, a posteriorly open marginal frame (loss of M5 and $${\text{M}}_{5}^{'}$$ ), a zygal plate in central position, and confluent, sutured M3 and G; (2) anomalocystitids derive from Mitrocystites-like mitrocystitidans by modification of two marginals (digital and glossal) into posterior spines. Two distinct terminologies are tentatively proposed for supracentrals in Allanicytidiinae and Anomalocystitinae, because the highly standardized plate patterns of their Siluro-Devonian representatives were possibly acquired independently in the two clades.
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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".