First report of <i>Sphenothallus</i> Hall, 1847 in the middle Cambrian
Bibliographic record
Abstract
Sphenothallus Hall, 1847 is a widespread Paleozoic marine taxon that has been interpreted most recently as a tubiculous annelid or other ‘worm’ or as a thecate hydrozoan or scyphozoan cnidarian (e.g., Mason and Yochelson, 1985; Feldmann et al., 1986; Van Iten et al., 1992, 1996; Neal and Hannibal, 2000; Zhu et al., 2000). Members of this genus are characterized by a very gently tapered, finely lamellar apatitic tube bearing a closed subconical holdfast and a pair of robust longitudinal thickenings situated at the ends of the tube's greatest diameter (Zhu et al., 2000). Rarely, the tube exhibits an internal transverse wall that extends adaperturally along the inner surface of the tube proper and may also exhibit a subcylindrical terminal protuberance (Van Iten et al., 1992, figs. 5, 6). The transverse wall of Sphenothallus is essentially identical in gross morphology and microstructure to the schott (apical wall) of conulariids, an extinct group of thecate cnidarians (Van Iten, 1991, 1992a, 1992b; Jerre, 1994; Van Iten et al., 1996; Hughes et al., 2000) that may have been closely related to Sphenothallus (Van Iten et al., 1992). Clarke (1913, pl. 26, figs. 16-18; see also Van Iten et al., 1992, fig. 3) illustrated a compound specimen of S. sica consisting of numerous “daughter” tubes arranged in a highly regular manner (in opposition and evenly spaced) along a single, relatively large “parent” tube whose test wall appears to be confluent with the base of the “daughter” tubes. This compound specimen is distinctly different from the more common associations of epibiontic, holdfast-bearing Sphenothallus arranged in a less orderly fashion on Sphenothallus tubes or other shells (see for example Feldmann et al., 1986, fig. 2), and probably is best interpreted as a clonal colony. Sphenothallus tubes, both solitary and branched, are most similar to thecae of solitary and colonial hydrozoan and scyphozoan polyps, differing from these relatively delicate structures mainly in being mineralized and in bearing a pair of longitudinal thickenings. Like conulariids, Sphenothallus occurs in rocks originally deposited in a broad spectrum of marine facies (open carbonate shelf to restricted shale basin), but is perhaps most conspicuous in restricted basin and shelf slope facies represented by dark shales and lime mudstones.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.002 |
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".