Morphometric analysis of the conodont <i>Chiosella timorensis</i> (Nogami) from the early Anisian of Romania and China, and its significance for the definition of the Olenekian–Anisian Boundary
Bibliographic record
Abstract
Abstract The conodont Chiosella timorensis (Nogami) has long been proposed as a biotic proxy for identifying the Olenekian–Anisian Boundary (OAB). However, uncertainty regarding the relationship between this species and the morphologically related species Ch . gondolelloides (Bender) and its stratigraphic range have cast doubt on its suitability as a proxy. Morphometric analysis of large populations of Chiosella from the global stratotype section and point (GSSP) candidate at Deşli Caira, southeastern Romania, as well as other OAB sections in south China, demonstrate that most morphological variation in this genus is caused by variability in the position of the cusp, not the length of the mid‐lateral rib (traditionally used to separate the species Ch . gondoelloides and Ch . timorensis ). Furthermore, there is little to no stratigraphic separation between the two species, and no obvious trend in any of the investigated sections of a morphological shift from one species to the other with increasing stratigraphic height. Finally, when investigating the size variation of the population, it becomes apparent that in general, specimens assigned to Ch . gondolelloides are much smaller than those Ch . timorensis . Taken together, these results imply that most specimens of Ch . gondolelloides could be juvenile forms of Ch . timorensis . If Ch . timorensis is used as the biotic proxy for the OAB, then the results of this morphometric analysis necessitate the base of the Anisian being moved down in several OAB sections, including Deşli Caira. Despite this, the study provides greater taxonomic stability, enhancing the utility of Ch . timorensis for future stratigraphic correlation.
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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 | 0.000 |
| 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 | 0.000 | 0.000 |
| Open science | 0.000 | 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 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".