Early Permian conodonts from the Xainza area, central Lhasa Block, Tibet, and their palaeobiogeographical and palaeoclimatic implications
Bibliographic record
Abstract
The Tibetan Plateau, the highest plateau in the world, is relatively difficult to access. Therefore, the stratigraphy and fossils in this area are poorly known, although they are very important for interpreting the palaeogeographical evolution of different tectonic blocks. Here we report the new discovery of an abundant conodont fauna from the lowest part of the Xiala Formation in the central part of the Lhasa Block, Tibet. This conodont fauna includes three genera and four species (Mesogondolella idahoensis, M. siciliensis, Vjalovognathus nicolli Yuan, Shen & Henderson sp. nov. and Hindeodus sp.). The conodont fauna indicates that the lowest part of the Xiala Formation is late Kungurian in age based on the presence of abundant Mesogondolella idahoensis and the denticle characters of Vjalovognathus nicolli sp. nov. The presence of the conodont genus Vjalovognathus, the associated small solitary corals and the absence of any fusulinids clearly suggest a cool-water condition in the lower part of the Xiala Formation. Thus, the Xiala Formation in the central Lhasa Block can be restricted to an age from late Kungurian to Wuchiapingian. This is in contrast to the warm-water faunas consisting of abundant fusulinids, compound and large solitary corals, and warm-water conodonts in the upper part of the Xiala Formation from late Guadalupian to Wuchiapingian in age. This dramatic faunal change suggests that either the palaeoclimate had greatly changed from a cold condition to a warm condition after the late Kungurian in the peri-Gondwanan region, or the palaeogeographical position of the Lhasa Block had drifted northward into the warm-water regime from the late Kungurian to Guadalupian. The new family Vjalovognathidae Shen, Yuan & Henderson fam. nov. and the new species Vjalovognathus nicolli Yuan, Shen & Henderson sp. nov. are proposed, based on abundant specimens from central Tibet.http://zoobank.org/urn:lsid:zoobank.org:pub:35EFEF79-315E-4CCE-A72E-5BE27CFAFBF5
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.001 | 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".