Permian spiriferellid brachiopods from northern Pangaea: taxonomy, biostratigraphy, macroevolution and implications for palaeoenvironmental and palaeobiogeographical reconstructions
Bibliographic record
Abstract
This study reports diverse spiriferellid brachiopods from the Permian rocks of Svalbard and adjacent areas (Arctic Canada and Subpolar Urals of Russia) located at the northern margin of Pangaea. In total, 11 brachiopod species in four genera are recognized and described in detail, including two new species (Spiriferella protodraschei and Arcullina? enokiani). According to our taxonomic investigation, morphological characteristics of the ventral sulcus and dorsal fold are relatively stable within each species, in spite of considerable intraspecific variations in shell outline and macro-ornamentation. In addition, both the arrangement of pustules, as a shell surface micro-ornamentation, and the development of delthyrial coverings are shown to be significant features for inferring phylogenetic relationships and for defining species. The best-known but still questionable taxon, Spiriferella keilhavii, is here identified as an endemic species restricted to Bjørnøya and, possibly, to central East Greenland; it is phylogenetically closest to S. loveni. Following the taxonomic revision, the stratigraphical ranges of the spiriferellids within the Kapp Starostin Formation in Spitsbergen are fully refined: three species, S. protodraschei, A. polaris and Timaniella wilczeki, are confined to the lowermost Vøringen Member (late Artinskian–early Kungurian), whereas S. loveni dominates the overlying members with a much longer stratigraphical range (late Kungurian–Lopingian?). This abrupt compositional change, along with comparable changes in other taxonomic groups, can be explained by a palaeoclimatic shift from cool to cold conditions between the Vøringen Member and the overlying Svenskeegga member. A similar biotic transition is identified between the Hambergfjellet and Miseryfjellet formations in Bjørnøya. On the other hand, S. loveni is abundant in the Late Permian strata of central East Greenland, but there it appears to be more costate in plication compared to its counterpart from Spitsbergen. It is suggested that this alteration in shell ornamentation may represent a possible response (adaptation) to warming arising from the southward migration of the species.http://zoobank.org/urn:lsid:zoobank.org:pub:85B863D2-DB42-4835-940A-2DE852C82178
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| 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) | 0.001 | 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".